949
SECTION III
NEUROSURGERY
CHAPTER XI
TECHNIQUE
OF
NERVE SURGERY
INTRODUCTION
In
presenting a system of technique on the operative treatment of
peripheral nerve lesions,
it is assumed that the reader is familiar with the histopathology and
pathologic physiology of
peripheral nerve tissue when visited with disease or subjected to
injury: it is only on the basis of a
thorough understanding of the histologic and physiologic principles
involved that a rational
operative treatment may be founded. Fortunately, these principles,
placed pon a sound footing
more than two decades ago, have been amply verified by subsequent
experimentation and
consistently upheld by the innumerable clinical observations afforded
by the vast amount of
material supplied by the casualties of the World War. The conclusions
arrived at by Howell and
Huber in 1891, in their many experimental studies of peripheral nerve
physiology, degeneration,
and regeneration may still serve as a general text for a rational
system of procedure in the
operative treatment of peripheral nerve lesions.
Probably
in no other type of surgery will the end results so emphatically
demonstrate the
necessity of subserving physiologic principles. It has been generally
known that the fibers of one
nerve trunk, when anastomosed to the distal segment of another nerve,
will regenerate
satisfactorily through the adopted nerve: this fact was utilized in
hypoglosso-facial anastomosis
for the correction of facial paralysis, though the principle governing
this procedure was not based
upon a complete physiologic appreciation of all the factors involved.
This operation
demonstrates the principle of anatomic surgery, in which fibers are
supplied to the denervated
muscles of the tongue by the anastomosing of one nerve into another.
The physiologic principle
ignored in this type of anastomosis is manifest in the end results,
namely, the paralyzed facial
muscles, though having regained some motor power, still remain immobile
to emotional facial
expression, contracting synchronously with lingual movements during
mastication or deglutition.
While the paralyzed facial muscles were re-innervated, the innervation
from a physiologic
standpoint was doomed to failure, because the new fibers innervating
the facial musculature are
hypoglossal fibers, capable of subserving hypoglossal function
only-motor function to the
tongue--which is in no way correlated to the emotional reactions
expressed through the facial
musculature. This represents but one type of physiologic transgression
in the surgery of nerves.
Most
peripheral nerves are both motor and sensory in functions; the motor
portion of the
nerve trunk, derived through a neuraxon outgrowth from the motor cells
in the anterior horns of
the spinal cord, carry efferent motor impulses: the sensory portion of
the nerve trunk is composed
of fibers which carry
950
sensory or afferent
impulses through the posterior horns of the cord. These motor and
sensory
fibers, though anatomically incorporated within a single nerve trunk,
are from a physiologic
standpoint totally unrelated; this well-known physiologic fact, when
given due consideration,
immediately elevates the operation of nerve suture from the domain of
anatomic to that of
physiologic surgery. The anatomic principle of simply obtaining a
satisfactory end-to-end approximation of a divided peripheral nerve,
adequate to permit the passage of regenerating
fibers, does not suffice in nerve surgery, for it may, from a
physiologic standpoint, be very
imperfect. in that the motor fibers in regenerating may enter sensory
channels leading to sensory
terminations, and these motor fibers, not being able to subserve
sensory function, would be
physiologically lost.
A
study of the end results following nerve suture has amply demonstrated
that perfect
anatomic sutures are frequently attended by only a partial restoration
of function, and
occasionally by its total absence. At best, the unqualified anatomic
principle of nerve suture,
without regard to the physiologic differentiation of fibers, can be
nothing more than a hit-or-miss
method of procedure. If in the approximation of the ends of the divided
nerve the surgeon is
fortunate enough to approximate motor fibers to the motor channels in
the distal segment and
sensory fibers to their respective channels, the ultimate results-if
regeneration is unimpeded in
both nerve and muscle-should be a complete restoration of function. The
possibility of a
physiologic approximation, if left wholly to chance as in an ungoverned
anatomic suture, can be
seldom expected, though in the majority of instances some motor fibers
will probably (by
chance) reach motor channels and regenerate to a motor termination; no
doubt many will be
lost, and our experience seems to indicate that the regenerating motor
and sensory fibers are
incapable of selecting their respective physiologic channels. The
principle of physiologic
approximation resolves itself almost entirely into the prevention of
torsion of the nerve trunk
during suture; the most important factor involved in the technique of
nerve surgery depends
upon our ability to prevent or correct this unfortunate incident. While
end-to-end approximation is absolutely essential to neuraxon
regeneration, physiologic approximation is indispensable
to the restoration of function.
An
adequate conception of physiologic principles will immediately enable
the surgeon to
disregard many of the older operative procedures of nerve anastomosis,
more or less brilliant
from a purely anatomic standpoint. hut absolutely futile when
considered in the light of our
present knowledge. An appreciation of the fact that each fiber within a
nerve trunk has to a
greater or lesser degree some functional individuality should lead the
surgeon to a realization
that, though it is within his power to change the anatomic course of
these fibers, their physiologic
attributes remain unchanged; at best, his most painstaking and careful
operative manipulation,
however ingenious from an anatomic standpoint, loses in functional
value in direct proportion to
the perversion of the original physiologic pattern. Satisfactory end
results in nerve surgery
depend primarily upon a full appreciation of physiologic function and
our ability to conserve the
anatomic characteristics compatible with the normal expression of that
function.
951
THE GENERAL
TECHNIQUE
ANATOMIC REQUIREMENTS
Primarily
it is essential that the operator have that practical working knowledge
of
peripheral nerve anatomy which is acquired and maintained only by
frequent recourse to the
dissecting room. It is particularly important that he be familiar not
only with the general course
and relationship of nerve trunks, but also the origin and distribution
of the various branches its they arise; it is not only essential that
these branches be preserved in dissection, but they must
also be exposed and accurately identified in order to determine, by
their intraneural position, the
intraneural topography of the nerve trunk. While no dogmatic rule may
be laid down regarding
the point of separation-superficial origin-of branches from the parent
trunk, their intraneural
course, as a rule, is sufficiently constant to permit a fair degree of
accuracy in topographical
identification. It is usually necessary that the particular branch
under consideration be liberated
for a short distance up the nerve trunk, in order that its exact
intraneural position be accurately
determined. Occasionally a motor branch may have its superficial origin
from the sensory side of
the nerve trunk, but its deep intraneural position will usually be
found to be in that sector of the
nerve trunk which contains the motor bundles. The exposure and
identification of motor and
sensory branches, arising from a peripheral nerve, is of exceedingly
great value in topographical
localization, as their intraneural localization will nearly always
indicate that portion of the nerve
trunk which subserves their respective function, either motor or
sensory.
PREPARATION OF AN EXTREMITY FOR OPERATION
It
is important in nerve operations that the skin of the entire extremity
he sterilized from a
point some distance above the proposed incision. The necessity of
sterilizing the peripheral
portion of the extremity is due to the fact that manipulation of the
entire limb is frequently
necessary during an operation; the observation of the entire limb
during electrical stimulation of
the nerve is essential to determine the action of individual muscles.
This is particularly important
in the hand. Occasionally a sterile rubber glove may be used to cover
the hand of the patient,
when adequate sterilization is doubtful. The glove usually will permit
observation of muscle
action. The draping of an extremity should always he arranged in such a
manner as will facilitate
observation and manipulation without contamination; the surgeon should
personally direct the
placing of protective sheets and towels with this object in view.
POSITION
The
position of an extremity, for operation upon one of its principal
nerves, should be
planned with as much forethought as might be given to any other step of
the operation; the
surgeon should endeavor, by the effective placing of sand bags, to
maintain the extremity in a
position conducive to the comfort of the patient as well as to his own
convenience. A third
assistant, or a sterile nurse with specific instructions, should be
retained to maintain the extremity
in the desired position of flexion, when flexion-relaxation is utilized
in the correction of
continuity defects.
952
ANESTHESIA
Local
anesthesia, in the writer's experience. has supplanted all other types
of anesthesia
for peripheral nerve work. Its proper use is attended with complete
analgesia, with the retention
of motor function. It permits the use of the electro-anatomic method of
funicular identification; it
greatly diminishes the oozing encountered in scar tissue dissections:
and avoids the disagreeable
complications attending inhalation anesthesia.
The
following technique is used in produtinlg local anesthesia: At 1
percent solution of
novocaine or procaine is used, to each ounce of which 15 minims of a
fresh 1:1,000 adrenalin
chloride solution has been added. The line of proposed skin incision is
carefully infiltrated,
producing a continuous line of intradermnal wheals. The needle is now
passed into the
subcutaneous tissue for a depth of 112 cm., where 1 c.c. of the
solution is injected; the needle is
then directed deeper and a second injection is made. Without
withdrawing the needle, which
should be sufficiently long to reach the nerve, these injections are
made at an increasing depth
until the tissues surrounding the nerve have been reached. These
subcutaneous injections are
made about 2 or 2 ½ cm. apart, along the entire line of the proposed
incision. At each injection,
in deep infiltration, particularly in the region of a large vessel, the
piston of the syringe should be
slightly withdrawn before any of the solution is injected, to determine
the possibility of an
intravascular penetration; if blood is aspirated the needle should be
redirected. It is usually
neither necessary nor desirable to inject the nerve until it is ready
for section. unless pain is
experienced. After the field has been thoroughly infiltrated, pressure
is used for a few minutes to
prolmote the diffusion of the solution througth the surrounding
tissues. If it be necessary to carrv
a dissection to the surface of a bone, its periosteum should be
infiltrated. When the incision and
surgical manipulations are confined to the infiltrated areas, they are
absolutely painless and
frequently bloodless; and, as most peripheral nerve operations are
attended with much scar tissue
dissection, this bloodless field is highly desirable.
EXPOSURE OF
THE NERVE
The
importance of long incisions and adequate exposures can not be too
greatly
emphasized in the surgery of peripheral nerves. It has usually been our
experience that at
seemingly adequate incision will require lengthening before the
operative procedure is
completed. This possibility should always be borne in mind during the
preparation of the skin
anil draping of the extremity for by so doing the surgeon will avoid
the risk which attends
invasion of parts not adequately prepared.
One
of the greatest mistakes a surgeon can make is to attempt the exposure
of a nerve in a
scar-invaded region; for safety's sake alone, without a consideration
of other advantages, the
surgeon should make it his invariable rule to expose the nerve above
and below the lesion, when
the location of the lesion will permit. The nerve, having been exposed
in a region where normal
anatomic relationships prevail, may then be followed through the
scar-invaded area where these
anatomic guides have been distorted or lost.
953
The
prevention of scar tissue following nerve operations is of paramount
importance;
and while it cannot be wholly obviated, there is no doubt but that it
may be greatly mitigated by a
careful operative technique. Scar tissue following surgical
intervention is usually the result of
tissue trauma, inadequate hemostasis, and infection. Tissue trauma may
be reduced to a
minimum by careful, clean-cut dissections, confined when possible to
normal lines of cleavage.
A common source of tissue trauma lies in the use of artery forceps and
the ligation of vessels.
When it is necessary to clamp a vessel, no more tissue than is
absolutely necessary should he
crushed to secure the vessel. The habit of crushing, and ligating the
entire area around a vessel is
greatly to be deplored, as it is accompanied by considerable tissue
strangulation and subsequent
necrosis, inviting infection and scar formation. Blunt and finger
dissection, which is so
frequently associated with tissue tearing and extensive trauma has no
place in the surgery of
peripheral nerves. The use of antiseptics, such as iodine, within the
wound is to be condemned. It
is desirable to cover the skin edges with clamped towels, as complete
skin sterilization is often
questionable. Parts of the incision which are not receiving immediate
attention many be
prevented from drying and protected from contamination by cotton pads
saturated with warm saline. Scar tissue dissections, which under
general anesthesia would be associated with constant
oozing, are often rendered blood- less by infiltration anesthesia, and
by the time the constricting
action of the adrenalin has disappeared clotting has occurred in those
oozing points which so
often defy ligation. A time-saving procedure in the dissection of
neurovascular bundles is
preliminary control of the circulation by isolation of the veins below
the lesion and the artery
above, which structures may be temporarily constricted by tape to
control hemorrhage following
vascular accidents. Nothing is more deplorable than to see a surgeon
blindly attempting to grasp
an unseen bleeder in a pool of blood: in nerve surgery such a procedure
is fraught. with so great a
degree of danger to nerve trunks and branches that it is inexcusable,
in that it may usually be
obviated by using sufficient precaution for vascular control.
DEFECTS IN
NERVE CONTINUITY
When
at nerve is divided its ends tend to retract in the surrounding loose
connective
tissue, where they become fixed with the process of healing and the
formation of scar tissue,
making a defect in nerve continuity. In certain instances a portion of
the nerve trunk may be
completely destroyed or traumatized to such an extent as to obliterate
its recognizable anatomic
continuity. More frequently, however, the nerve so suffers from the
devastating effect of
infection and subsequent scar-tissue proliferation that large sections
must be sacrificed before
normal-appearing nerve bundles are found in its ends.
Various
procedures have been recommended for the correction or filling of nerve
defects,
many of which have little, if any, physiologic grounds for support.
Technically, some of the
procedures recommended for the filling of defects, such as the
interposition of tubes and various
other foreign materials, may appear to be very ingeniously conceived,
but from a physiologic
standpoint they were often so defective that the probability of
recovery was actually
954
minimized by the
procedure. To permit nerve regeneration, direct anatomic approximation
of the
nerve ends must he attained. In certain instances when this is found to
be impossible, the use of
the autogenous cable graft is justified for filling defects, but at
best it seems to promise but a very
moderate degree of functional restoration. The interposition of
heterogenous nerve grafts has
been so universally unsuccessful in clinical experience that their use
is to be discouraged.
Various procedures, such as nerve implantation into neighboring nerves
and the neurotization of
paralyzed muscles, have so little to recommend them from a practical
standpoint at the present
time that they may be dismissed from the category of effective clinical
procedures.
The
following methods of correcting continuity defects in peripheral nerves
are the only
ones whose functional end results, in our experience, justify usage:(1)
Primary nerve stretching;
(2) flexion-relaxation; (3) nerve transposition;(4) stretching with
secondary suture (two-stage
operation); (5) autogenous cable grafts; (6) viable neuroplastic
transplants; (7) bone shortening.
PRIMARY STRETCHING
Primary
stretching will overcome many of the lesser defects. It consists of
freeing the
nerve trunk beyond the area of scar tissue fixation and drawing its
ends together by gentle
traction. Extensive mobilization of a nerve trunk permits a
proportionately greater stretching. It is
particularly necessary to freely mobilize the nerve beyond the region
of extraneural adhesions,
but in doing this, great care should be exercised in avoiding injury to
branches.
FLEXION-RELAXATION
The
majority of nerve defects may be corrected by taking advantage of the
relaxing effect
upon a nerve trunk, by flexion of governing joints. The approximation
of the nerve ends is made
possible, after the nerve is prepared for suture, by flexing the
governing joint, in which position it
is maintained, after the nerve is approximated, by suitable splints
until the wound is healed; after
which the mobilizing splints are occasionally changed to permit a
gradual extension of the flexed
extremity. In our study of end results of nerves under tension or those
stretched by the foregoing
method, we have not found that this stretching seriously interferes
with regeneration; in fact,
some of our best end results have been observed in cases where
approximation was attainable
only under considerable tension. In our early experience, when
flexion-relaxation was used in
overcoming large defects, we maintained the limb in the position of
primary flexion for a period
of six weeks; later, however, this period of fixed flexion was reduced
to two weeks, after which
the gradual extension of the extremity was permitted at the rate of
approximately ten degrees
every second day.
NERVE TRANSPOSITION
The
course of certain nerves in the arm may be made more direct and thereby
shortened
by transferring them from a dorsal to a more ventral plane. This
procedure is commonly used to
great advantage in overcoming the more extensive defects.
955
The
ulnar nerve in its normal position behind the internal condyle is not
relaxed by
flexion of the elbow until it has been transposed to a position
anterior to the internal humeral
condyle. This procedure not only somewhat shortens its course but also
renders it susceptible to
flexion-relaxation. The musculospiral nerve is occasionally transposed,
being directed from its
posterior humeral course to one anterior to the humerus. Large defects
in the median often
require for their correction a transposition of the nerve from its deep
position below the
superficial head of the pronator teres to one ventral to this muscle.a
In
the transposition of nerves it is essential that the operator be
familiar with the various
branches given off from that portion of the nerve trunk requiring
mobilization; these branches
must be freed some distance up the nerve trunk by an intraneural
dissection to permit
mobilization without their avulsion. It is also essential to place
topographical markings on both
proximal and distal segments of the nerve by means of well placed
identification sutures, before
the position of these segments has been disturbed and anatomic
relationships lost, in
mobilization.
STRETCHING, WITH SECONDARY SUTURE (TWO-STAGE
OPERATION)
After
a divided nerve has been exposed and found to present a defect, the
surgeon should
determine means of correcting this defect before the neuroma anti scar
tissue have been excised
from the ends of the nerve. If it be found that the defect will not
lend itself to correction by one of
the foregoing methods, the operator must then resort to the two-stage
operation. This consists
inextensive mobilization of the nerve trunk after it has been marked
with topographical
identification sutures, and all possible relaxation has been attained
by transposition and flexion-relaxation. The unsectioned nerve ends are
drawn together by one or two strong chromic catgut
traction sutures using sufficient tension to permit, if possible, an
overlapping of the nerve ends to
a point approximating that which will correct the defect, after the
sear tissue has been resected; or
at least, to obtain as much overapproximation as possible. The wound is
now closed, and after
one week the extension of the extremity begun, the object being a
gradual stretching of the nerve
trunk. When this has been accomplished by complete extension of the
extremity and the wound
is entirely healed so that it is safe for a secondary aseptic invasion,
the nerve is again exposed;
the neuroma and scar tissue are resected and the freshened ends
approximated by again utilizing
the assistance of flexion-relaxation. The extremity is splinted in this
position for a period of two
weeks, after which extension is gradually encouraged. Many of the
defects encountered in
extensive lesions of nerves have been corrected by a two-stage
operation, and only when the
nerve defect is of such magnitude as not to be corrected by the above
method are we justified in
resorting to grafting.
NERVE GRAFTS
From an experimental standpoint, nerve grafting has
attracted
considerable interest and
much has been expected from this procedure; from a clinical standpoint
a The
technique of transposing the above nerves
is considered in detail under the surgery of special nerves.
956
however, the end
results have been very disappointing. A review of end results in so far
as functional restoration is concerned, in 15 cases in which the
operations were done by different
operators, shows that functional restoration was nil, with the
exception of one instance in which
there was some return of sensation in a low median graft. (This
restoration consisted, after four
years, in simply the restoration of a nondiscriminative sensation in
the index and middle fingers.
All sensation, including touch, pin prick, heat, and cold, were
interpreted as tingling-differentiation not being possible.) In the
writer's experience, a number of homogenous
refrigerator grafts were tried out; in each instance the condition of
the wound was favorable and
remained so throughout the healing process, though in no case was there
any clinical evidence of regeneration. These grafts when subsequently
removed showed a total absence, histologically, of
nerve fiber regeneration, and the proximal end of the nerve trunk
exhibited a secondary
neuroma. In most of the above instances it was later found possible to
obtain satisfactory end-to-end approximation by the above-described
two-stage operation. With increasing experience in
dealing with large defects, we found that in most instances it was
possible to repair the defect by
a two-stage operation. thereby almost entirely eliminating the
necessity for grafts. Occasionally, however, defects are found of such
magnitude that the only possibility of nerve repair lies in
grafting, but as a rule such cases, by virtue of their severity, the
extent of tissue destruction and
scar tissue formation, promise but little in the way of satisfactory
functional restoration. It must
be remembered that the experimental work of nerve grafting which has
been attended with such
satisfactory results has been done in relatively small defects under
extremely favorable
conditions from a surgical standpoint. Such satisfactory conditions are
rarely encountered
clinically because of the severity of the original lesion which makes
nerve grafting necessary.
AUTOGENOUS CABLE GRAFTS
Autogenous
cable grafting consists in exposing the end is of both proximal and
distal
segments of the divided nerve and preparing them for suture. The length
of the defect between
the nerve ends is measured and the grafts to be inserted are selected
from convenient sensory
nerves. In the arm the following nerves may be utilized: Radial
(sensory portion of the
musculospiral), sensory portion of the musculocutaneous, internal
cutaneous. In the leg:
Sensory portion of the musculocutaneous, tibial, and peroneal
recurrent, the sural branches of the
peroneal nerve. One or several segments from one or more of the sensory
nerves, of sufficient
length to fill the defect, are removed and transplanted to fill the gap
between the ends of the
damaged nerve. These sensory branches are usually so small that several
are required in making
a cable which will approximate in size the nerve trunk. After a cable
graft of sufficient size a1l
length is obtained, it is carefully anastomosed to the ends of the
nerve trunk and in this way made
to bridge the defect. It is essential to obtain accurate end-to-end
approximation between both
ends of the nerve trunk and graft. If a defect in a small nerve is
being bridged, it may be possible
to obtain sensory graft of approximate size, thereby eliminating the
necessity of using
957
several grafts as it,
cable. It is particularly important that a favorable bed be found to
protect the
grafted nerve. The writer, in the removal of a number of unsuccessful
grafts, has found them
converted into strands of fibrous tissue; in at few instances some
regenerating neuraxons Were
found to have penetrated the proximal end of the implant, but in none
had they succeeded In completely traversing, the graft.
VIABLE NEUROPLASTIC TRANSPLANTS
In
irreparable defects of combined nerve lesions, such as the median and
ulnar or the
tibial and peroneal portions of the sciatic trunk, the writer, by
sacrificing the nerve of lesser importance, devised a method of filling
the defect in the more important nerve with at viable transplant. In
this procedure for example for, in a combined median and ulnar
irreparable defect, the median considered to
be the nerve of greater importance, the end of its proximal segment is
anastomosed by end-to-end suture to the proximal end of the ulnar
nerve--the nerve of lesser
importance--permitting the median fibers
FIG. 150.– Bundle or “cable”
graft, using an
autosensory nerve for repair of the defect. (Ney, Annals of Surgery,
1921)
to regenerate around the
loop) so formed by the anastomosis and up the ulnar trunk. The ulnar
nerve
is divided the required distance (length of median defect) above its
anastomosis to permit the
degeneration of its fibers in that portion of the trunk which
subsequently is to be used as a
transplant, thereby preparing it to receive the regenerating fibers of
the mendian nerve. The trunk
of the sacrificed ulnar nerve remains undisturbed in its original
position, to conserve its nutrition
during the migration of median fibers through its entire length. Before
the transplant is utilized,
it is allowed one month for each inch of its length plus one month's
grace, to assure regeneration
through its entirety. The upper end of the adopted trunk may be placed
subcutaneously if desired,
where it ran he readily palpated and percussed to determine the growth
of nerve fibers to its
extremity--the presence of regenerated fibers may be readily
demonstrated by Tinel's sign, thus
assuring the surgeon of the viability of the transplant before it is
turned down at the second stage
of the operation.
The
advantage of the viable neuroplastic transplant is that its nutrition
is maintained
during neuraxon regeneration, and at the time of use it has, to
958
all intents and
purposes, become a viable part of the nerve trunk, containing intact
and viable
neuraxons. It then may be united to the distal segment of the nerve
with all the advantages of a
direct approximation. The writer has restricted its use to the repair
of inoperable combined
lesions in which he felt justified in sacrificing a permanently
disabled neighboring nerve. The
possibilities of the viable neuroplastic transplant will probably be
extended with experience as it
seems at the present time to be our only practical method of filling
nerve defects. The results
following the use of the viable transplant are comparable to those
following direct
approximation.
BONE SHORTENING
Bone
shortening is occasionally justified for the correction of large nerve
defects, though
the arm should not be shortened until full advantage is taken of other
means to correct the defect.
Shortening of the upper extremity does not, of itself, produce serious
disability, but obviously
such a procedure would not be practical in the lower extremity. Before
recourse is taken to bone
shortening the two-stage operation of nerve stretching should be tried;
if this fails by a few
centimeters to correct the defect, humeral shortening to this extent
may be practiced to assist the
other procedure. When a section is removed from the humerus for the
purpose of shortening the
extremity to permit coaptation of divided nerves, the resection is
usually done in its lower third,
care being taken to prevent injury to the musculospiral nerve if the
exposure is carried into the
middle third. The bone may be divided with a Gigli saw, after which it
is dislocated through the
incision and a section sufficiently long to correct the defect removed.
The ends of the bone are approximated before suturing the nerve, by
bone plates or a medullary graft, or by their
combination. It is particularly important in approximating the nerve
and closing the incisions to
prevent unnecessary movement which might disturb the position of the
bone or throw undue
strain upon the bone plate, or graft. The arm should be carefully
immobilized with plaster to a
body cast which has been applied before the operation, and so
maintained for a period of six
weeks or until firm bony union has taken place. A window should he made
in the cast which will
permit inspection of the wound and change of dressings when necessary.
The skin is sutured with
catgut to prevent the disturbance of suture removal.
ANKYLOSED JOINTS WITH NERVE DEFECTS
Occasionally
an ankylosis of the elbow or knee joint will prevent the utilization of
flexion-relaxation in overcoming continuity defects in nerve. The
advisability of resorting to
arthroplasty for the correction of ankylosis in these joints will
depend greatly upon the disability
resulting from the combined nerve and joint lesion. Much has been said
for and against
arthroplasty as a practical procedure; many surgeons of experience are
in favor of allowing these
joints to remain ankylosed, providing their position is useful. The
writer is inclined to believe
that in many instances very satisfactory results will follow a
well-planned and carefully executed
arthroplasty; this is particularly true of the elbow, when the
ligaments have not been extensively
destroyed.
959
A flail-joint, however,
is more disabling than one ankylosed in the position of maximum
usefulness. If arthroplasty has made it possible to repair the nerve
and restore function in the
paralyzed muscles, even though it result in a flail-joint, it has
served at useful purpose, for the
joint may again be ankylosed in a convenient position.
IRREPARABLE NERVE DEFECTS
The
neurologic surgeon, in about 5 percent of cases, will meet continuity
defects in
injured nerves of a magnitude so great as to preclude the hope of
successful nerve repair. In such
instances he must resort to various supplementary procedures which will
promise some degree of
ultimate functional usefulness in the injured extremity. From a motor
standpoint, tendon transplantation frequently offers a fairly
satisfactory solution of the problem. In other instances, the
immobilization of joints must be resorted to; this procedure is of
value in deltoid paralysis, in
upper plexus lesions with loss of elbow flexion, and in stabilizing the
foot in irreparable lesions
of the sciatic nerve. These various supplementary surgical procedures,
though ordinarily falling within the realm of orthopedic surgery,
should be done, or at least directed, by the neurologic
surgeon, who is familiar with the neurologic aspects of the case. This
is particularly important in
tendon transplantations, which require a thorough knowledge of the
existing motor status of each
individual muscle utilized in the transplantation, if one is to obtain
the most satisfactory functional end results. b
TORSION OF THE NERVE TRUNK DURING SUTURE
A
most serious eventuality in the repair of nerves is torsion of the
nerve trunk during
suture. Many surgeons have been content to obtain a satisfactory
end-to-end approximation of the
divided nerve, but a physiologic appreciation of the functional
individuality of the various
bundles within the nerve trunk should tend to discourage such a
procedure as being manifestly
inadequate, for the final results are greatly inferior to those of a
technique where due regard is
paid to physiologic approximation. There are very few instances in
which it is not possible to
obtain at least some idea of the topographical anatomy of the nerve
trunk before suture, and the
surgeon who has not the ability, time, or patience to use the
physiologic technique in all its
phases is not justified in attempting the repair of peripheral nerves.
There
is no evidence at our command, and much to the contrary, to verify the
ability of
motor and sensory fibers to find their respective physiologic channels
during regeneration
through the distal segment of a divided nerve trunk. If motor fibers
are placed in contact with the
sensory channels of the lower segment, these regenerating motor fibers
will follow the sensory
channels, into which they have been directed, to a sensory termination,
and be physiologically
lost; it is not possible for motor fibers to subserve the function of
sensation, nor are sensory
fibers capable of carrying efferent motor impulses
b Supplementary procedures applicable to
individual nerves are considered in detail under the surgery of special
nerves.
960
to muscles, if, during
suture, they should be directed down motor channels. This physiologic
misdirection of nerve fibers is probably responsible for much of the
defective end results
attending the surgery of peripheral nerves; and while our present
technique is not sufficiently
refined to differentiate accurately the position within the nerve trunk
of these respective motor
and sensory bundles, it is possible for the surgeon, with a fair degree
of accuracy, to maintain the
physiologic alignment of the nerve during suture by the use of the
following methods: (1)
Identification sutures; (2) forceps identification; (3)anatomic or
branch identification; (4) electro-anatomic method.
IDENTIFICATION SUTURES
Identification
sutures are placed at a corresponding point in both proximal and distal
segments of the nerve sheath before the normal position of the nerve
has been disturbed by
dissection; the purpose of these sutures is to identify a definite
circumferential point upon the
nerve trunk which will permit, during approximation, a restoration of
original anatomic
alignment without torsion. It is well that these sutures be placed some
distance above and below
the lesion where normal anatomic landmarks prevail and where the nerve
has not been subjected
to torsion through the contraction of scar tissue. This procedure is
undoubtedly the simplest and
perhaps the most efficacious method of preventing torsion. Two sutures
may be placed, one
above the other, to assist in more accurate alignment. When the scar
tissue is resected from the
nerve ends preparatory to suture, these identification markings should
be lined upmost carefully
and the approximation sutures placed in a manner which will maintain
this alignment.
FORCEPS IDENTIFICATION
From
the standpoint of technique, forceps identification offers certain
advantages and
may be used in conjunction with identification sutures, or
independently. As the nerve trunk is
exposed and before it has been completely freed from its bed, the nerve
sheath is grasped on each
side with very fine mosquito hemostats. These forceps are so placed on
both proximal and distal
segments that they locate exactly the center of the medial and lateral
aspect of the nerve, for the
purpose of permitting alignment; they also serve efficiently to
stabilize the nerve while it is being
sectioned. Unless care is used, the operator may rotate the nerve trunk
and produce torsion by
alignment of lateral forceps with medially placed forceps, if the
forceps used on each side of the
nerve trunk are of the same pattern. (To prevent this, the writer
identifies both laterally placed
forceps by tying a suture to the thumb piece, which will serve for
lateral identification in the
alignment.)
ANATOMIC OR BRANCH IDENTIFICATION
This
may be utilized in many locations to effect satisfactory alignment: it
is particularly
valuable in secondary sutures, when the surgeon has reason to believe
that due regard had not
been paid to physiologic alignment during the primary suture; it is
also of value in checking up
the accuracy of identification sutures.
961
A careful
study of a series of dissections has convinced the writer
that
both motor and
sensory bundles occupy within the nerve trunk a very definite and
relatively constant position. While no dogmatic rule may be given as to
the position of exit of a nerve branch from the parent
trunk, it may be generally stated that if the nerve sheath be opened
for a short distance a given
branch will invariably be found to originate from a definite position
within the nerve trunk. If a
motor branch be followed a short distance up the nerve trunk, it will
be found to occupy a
definite location which indicates the position of the motor bundles in
the nerve trunk. The
identification of motor branches springing, from both segments of the
divided nerve, when these
branches have received proper intraneural localization, will assist
materially in accurately
approximating motor segments during suture.
To
reiterate, if a motor branch to a given muscle is identified and
followed a short
distance up the nerve trunk until it has assumed a fixed intraneural
position, this position may be definitely regarded as the location of
the motor portion of the nerve. It may be termed the
motor sector; conversely, the other side of the nerve would be the
sensory sector. The utilization
of this information serves topographical localization and physiologic
identification
FIG. 151.- Diagram showing
the necessity of
determining the intraneural location of a given branch. A motor branch
may leave the sensory side of a nerve trunk, and intraneural dissection
is required to establish establish its deep
origin which represents the motor sector of the trunk; the superficial
origin of nerve branches is often misleading the
study of the topographical and varies considerably
when other methods,
such as identification when other methods, such as identification
sutures, are not to be relied upon. With the study of the topographical
anatomy of individual
nerves, this method of branch identification becomes of increasing
value. Obviously, the surgeon
who expects to use this method must familiarize himself with the
intraneural anatomy of the
nerve upon which he contemplates surgical invasions.c
THE ELECTRO-ANATOMIC METHOD
This
method presents certain refinements in topographical localization,
unattainable by
purely anatomic methods. In the lower segment, the motorportion of the
nerve trunk is localized
by the anatomic or branch identification method as described above; in
the upper segment, the
sensory side of the nerve trunk is localized by weak faradic
stimulation of its various bundles,
after the nerve sheath has been opened 2 cm. above the nerve end. The
technique of
c Under the
surgery of special nerves such detailed information as is now available
regarding the
method of anatomic identification is considered.
962
this procedure consists
in exposing the nerve by infiltration anesthesia, without injection of
the
nerve trunk proper. (See technique of local anesthesia, p. 952).Two
centimeters above the scar
invaded end, the nerve sheath is opened longitudinally and its pearly
white bundles exposed; two
or three of these bundles are isolated from intraneural connective
tissue by gently inserting and
spreading the blades of fine-pointed iris scissors parallel with the
course of the bundles. A single
bundle is then lifted upon a fine glass hook and subjected to very
gentle faradic stimulation with
a fine needle-pointed bipolar electrode. If a sensory bundle be
stimulated, the patient will
complain of a tingling sensation in the
FIG. 152.- Electro-anatomic
method of
topographical identification. A, Motor branches in both proximal and
distal segments serve to identify the motor sector of the nerve. B,
Motor sector of distal segment is identified by the
position of motor branches. The proximal segment, having no branches to
permit anatomic identification of
intraneural topography, the nerve sheath is opened and the nerve
bundles Identified by faradic irritation, which is
most effective in determining sensory bundles; occasionally the
stimulation of bundles at the end of a resected nerve
may give some assistance in topographical identification, though it is
of less value and the stimulation is difficult to control
normal cutaneous area
supplied by that bundle. If the current be too strong. the patient will
complain of pain. If a motor bundle be stimulated, the patient will
experience a sensation of
muscular effort due to stimulation of myosensory fibers. For example,
in the musculospiral
nerve, if a motor bundle be subjected to mild faradic irritation in the
arm, and the patient
experiences a sensation of " pulling up " of the wrist or straightening
of the fingers, the surgeon will know that he is stimulating motor
fibers to the carpal extensors or to the extensor
communis digitorum, and he has thus localized the motor side of the
nerve trunk above the
lesion. If, however, the patient experiences a
963
tingling sensation which
is localized on the dorsum of the thumb or hand, the surgeon is then
stimulating the sensory area of the nerve trunk.
The
electro-anatomic method of funicular identification consists,
therefore, in locating the
motor portion of the nerve trunk in the distal segment, by identifying
the intraneural position of
motor branches, while in the upper segment of the nerve trunk the
sensory portion is localized by
weak faradic stimulation; in approximation, the surgeon is thereby able
to effect a certain degree
of physiologic alignment. This method is of value principally in areas
where the upper segment
of the divided nerve is not giving off motor branches, such as the
median nerve in the upper arm.
After the identification of the physiologic constituents of the
proximal segment, the nerve trunk
may be anesthetized with novocaine, and the neuroma and scar tissue
resected, preparatory for
approximation. In the electrical identification of bundles, it is
essential to begin with the weakest
possible current, the needle points of the electrode being separated
not more than 2 mm.
Electric
funicular identification is an extremely delicate procedure, and it
requires the
greatest care and gentleness, particularly to insure a current
sufficiently weak to avoid pain on
stimulating sensory bundles; a current which can be felt on the tip of
the tongue is often too
strong for sensory bundle stimulation.
BUNDLE IDENTIFICATION
After
resection of the scar tissue from the ends of the nerve, the individual
nerve bundles
stand out prominently, and some surgeons have attempted to effect
funicular identification by
bundle matching. In Ney's experience this has not proved feasible,
because the bundles of the
lower segment, which are but the empty channels from which the
neuraxons have disappeared by
degeneration, in no way correspond either in number or in size with
the intact bundles of the
proximal segment.
APPROXIMATION TECHNIQUE
After
both segments of the divided nerve have been exposed and precautions
taken to
prevent torsion during approximation, and the surgeon has assured
himself of the possibility of
correcting the defect, the nerve ends maybe prepared for suture. The
resection of nerve ends,
however, must not be done if there is any possibility of having to
resort to the two-stage
operation to correct a defect.
In
preparing a nerve for suture, the neuroma of the proximal end is
resected in serial
sections about 1 mm. thick until normal-appearing nerve bundles present
themselves throughout;
this resection should be continued until the nerve bundles are free
from scar tissue. The resection
of the nerve end should be made with a very sharp instrument, and for
this purpose a new safety
razor blade held in strong forceps serves admirably. If it is desired
to preserve the sectioned ends
for further study, the order of their arrangement may be maintained by
stringing them upon a
piece of suture material, after which they may be placed in alcohol or
formalin. The end of the
distal segment does not present a typical neuroma as does the proximal
end and is often
964
FIG.
153.- Application of
forceps to an immobilized nerve during section. (Ney. Annals
of Surgery, 1921)
FIG.
154.- Sectioning of nerve ends for removal of neuroma and
scar tissue.
Method of
preserving sections in order of removal. (Ney. Annals of
Surgery,
1921)
965
found to taper off into
the surrounding scar tissue, in which it is lost. It should be
sectioned
carefully beyond the point of scar invasion to a point where the
bundles stand out freely, using
the same technique as that used in sectioning the proximal end.
After
the nerve ends have been prepared, the first fine silk suture is
placed, passing just
through the nerve sheath, not deep enough to encroach upon or to
constrict the bundles. The first
suture is of great importance, in that it
FIG. 155.- A, Technique of
end-to-end suture,
showing the placing of identification sutures before a nerve is removed
from sear tissue. B, Exposed nerve before resection of neuroma and scar
from its ends. C, Nerve resected,
identification forceps applied, and three quadrant sutures placed. (Ney.
Annals of Surgery, 1921)
should remain the guide
to alignment in the placing of subsequent sutures, and in the placing
of
this suture the alignment of identification sutures should be assured.
The second and third sutures
are now placed in the center of the medial or lateral quadrant of the
nerve trunk. The ends of
these sutures are rasped by forceps and not tied until all quadrant and
intermediate sutures are
accurately placed. In placing the fourth or posterior quadrant suture,
the nerve trunk is rotated by
passing the forceps holding the lateral suture
966
under the nerve trunk,
rotating it to the medial side, while the medial qualdrant suture is
pulled
over to the lateral side. This rotates the nerve trunk so that its
posterior quadrant is exposed,
when its suture may be accurately placed. Between each quadrant suture
one or more
intermediate sutures maybe required, depending upon the size of the
nerve trunk. Adjacent
quadrant sutures are held taut, during the placing of each intermediate
suture, to assist inaccurate
spacing. A sufficient number of sutures should always be used to assure
perfect approximation of
the nerve sheath, thereby preventing the neuraxons from wandering
outside the nerve trunk at the
suture line, where they would be
FIG. 156.- A,
Rotation of the nerve for the purpose of placing the posterior quadrant
suture. B,
Intermediate sutures placed and all sheath sutures held in position to
prevent rotation in placing a
tension suture. (Ney. Annals of Surgery, 1921)
physiologically lost and tend to form a sensitive
neuroma. After all suture shave been placed the nerve should be relaxed
by flexing the governing
joint and the nerve ends gradually approximated by taking in the slack
of the sutures. If
considerable tension upon the sutures is necessary to produce
approximation, a tension suture of
plain catgut may be passed completely through the nerve trunk 1 cm.
beyond its ends to diminish
the tension on sheath sutures. It is essential in placing the tension
suture that the forceps holding
the sheath sutures be equally arranged on each side, corresponding to
the sheath sutures of that
side, and these sutures held taut to prevent distortion of alignment
during its insertion. Care must
be exercised to prevent tearing of the sheath sutures
967
FIG. 157.- A, Approximation
by tension suture.
B, Order in which sheath sutures are tied after nerve is approximated
by the tension suture. C, End-to-end suture completed. (Ney. Annals
of Surgery, 1921)
FIG. 158.-The V section of a small
distal segment
used for the same purpose as the diagonal section in Figure 159.
(Ney. Annals of Surgery, 1921)
968
when force is required
to draw the tension suture through the nerve trunk. With all sheath
sutures held taut in their consecutive arrangement, the tension suture
is tied as the nerve ends are
approximated. The sheath sutures are individually picked up and tied,
beginning with those
placed proximal to the tension suture; as the sheath sutures are being
tied, every second suture is
left uncut to facilitate rotation of the nerve trunk for subsequent
inspection of the suture line. If
sheath approximation is found to be imperfect at any point additional
sutures may be placed for
its correction. Frequently, after sectioning the nerve ends, there is
some bleeding, which may
usually be controlled by
FIG. 159.- Diagonal section
of distal segment
where it is smaller than proximal segment, for the purpose of securing
accurate sheath approximation. (Ney. Annals of Surgery, 1921)
wet cotton compresses.
As the nerve is being approximated, care should be used to wash away
any blood clot which might have formed over the end of the sectioned
nerve. This clot should be
washed away, not wiped, as the traumatism of wiping will frequently
dislodge the clot, occluding
the end of the vessel, and the bleeding will be renewed.
THE PREPARATION
OF THE NERVE BED
When
the original nerve bed contains an excess of sear tissue, a
satisfactory new bed may
be provided by placing a few deep sutures through the adjacent muscles,
which may be drawn
together under the nerve, thereby burying the old bed and providing one
more favorable to the
needs of regeneration. It must be remembered in the preparation of a
nerve bed, however, that
scar tissue may be limited only by the avoidance of tissue trauma and
by
969
adequate hemostasis;
therefore, in interposing adjacent muscular tissue for the formation of
the
new bed, it is desirable that untraumatized muscle be used when
available. When scar tissue is
excessive and normal muscular tissue is not available for the
preparation of the nerve bed, the
nerve may be brought to a superficial position. Occasionally in
extensively scarred areas, neither
muscle nor superficial fat will be found available for the protection
of the nerve: it then becomes
necessary to transpose the nerve by directing its course through
adjacent intermuscular planes.
When, however, the length of the nerve does not permit transposition,
the surgeon must resort to
plastic procedures in which normal skin and superficial fascia from
adjacent regions are shifted
to cover the scarred area. When adjacent fat is not available for
plastic procedures of this type,
skin and fat from the abdominal wall may be transplanted by the
pedunculated flap method.
After
a satisfactory bed has been provided, all blood clots should be gently
washed away
by a running stream of warm saline solution. The common habit of wiping
incisions with gauze,
instead of sponging, is to be discouraged as it causes unnecessary
trauma to the wound and tends
to increase oozing. It is usually advisable to drain all incisions,
when there has been extensive
dissection, by one or two well-placed pieces of rubber dam, which
should be adequate to care for
any subsequent oozing. This drainage should be removed at the end of 48
hours.
PARTIAL NERVE LESIONS
Occasionally
a missile will sever only a part of a nerve trunk, causing a partial
lesion; or a
portion of the nerve may suffer accidental or intentional surgical
injury during debridement, or in
the removal of a nerve tumor. In several instances, the writer has
found fragments of bone driven
into the nerve trunk: in one case the musculospiral nerve had been
penetrated by a hypodermic
needle during typhoid inoculation, resulting in a permanent injury to
the fibers supplying the
extensor indicis. The majority of gunshot wounds involving the sciatic
trunk are partial lesions,
usually involving its external or peroneal portion. The frequency with
which partial lesions are
met adds greatly to their importance and demands special consideration,
for in the surgical
treatment of such lesions it is essential that the operator. in his
efforts at repair, does not inflict
additional surgical trauma to such intact nerve fibers as might have
escaped the original injury. A
careful preoperative determination of individual muscle function is
extremely important,
inasmuch as it should indicate the exact extent of nerve injury and
incidentally determine the
functional importance of intact nerve fibers.
TECHNIQUE OF REPAIR IN PARTIAL LESIONS
If
the nerve trunk, on exposure, exhibits a central or lateral neuroma,
partial excision and
approximation are required. If the preoperative examination indicates a
high degree of functional
integrity, the surgeon may rest assured that the “neuroma" is composed
mostly of scar tissue, and
its removal should
970
FIG. 160.- A, Partial lesion
of a nerve trunk.
B, Isolation of the interrupted portion from the physiologic normal
portion. Quadrant sutures placed for approximation. C, Approximation in
partial suture, such as a partial
division of the sciatic nerve, showing relaxed undivided portion of the
nerve. (Ney. Annals of Surgery, 1921)
FIG. 161.- A,
Partial lesion of a nerve trunk, where gross anatomic isolation of
functionally intact
portion of a nerve can not be made as in Figure 160. B, Opening of the
nerve sheath, showing in- volvement of bundle. C, V-shaped incision of
sheath by which
approximation of the bundle is
made possible. (Ney. Annals of
Surgery, 1921)
971
be attempted only after
the nerve trunk has been longitudinally opened for some distance, and
the normal bundles carefully separated from those incorporated in scar.
Such
bundles as appear to pass directly into the scar tissue should be
carefully isolated above and
below the lesion and subjected to weak faradic stimulation with a
needle-point bipolar electrode.
When faradic stimulation of a nerve bundle, distal to the lesion, is
accompanied by muscular
contraction (not due to diffusion of current), the surgeon may feel
assured that the bundle is
anatomically intact and should be dissected from the scar tissue with
great care, avoiding
traction, as nerve bundles are very easily torn. Bundles which give no
response during electrical
stimulation may not be anatomically divided, but only subjected to a
degree of compression
sufficient to destroy their conductivity; they should be carefully
followed through the scar tissue,
if possible, to determine their anatomic continuity. If a bundle shows
scar tissue infiltration, the
infiltrated area should be resected and the bundle ends approximated by
a single suture of arterial
silk passed directly through the bundle. When bundles are not readily
approximated because of a
defect, a V-shaped portion of
the nerve sheath may be resected, corresponding in width to the length
of the defect; linen sutures may be used to approximate this portion of
the sheath, and with
its approximation the ends of the individual bundles will be brought
together, overcoming their
defect; bundle sutures may then be tied, care
FIG. 162.- A,
Approximation of the divided bundle
accomplished by
relieving tension in the approximation of the
resected sheath, being used to obtain accurate B, The thickened sheath
is not entirely closed for fear of
strangulation; the defect is covered by a fat transplant. (Ney.
Annal of Surgery, 1921)
being used to obtain
accurate end-to-end approximation without strangulation. After
approximation of individual bundles has been satisfactorily effected,
the nerve sheath should be
only partially closed; the unclosed portion may be covered with some
surrounding untraumatized
tissue such as intact muscle sheath, or if this is not available, by a
pedunculated or free fat
transplant, extreme care being given to hemostasis. In partial lesion
of the sciatic trunk in which
preoperative examination reveals a total loss of peroneal or tibial
function, the nerve should be
exposed sufficiently low to obtain the natural line of cleavage between
its component parts,
which upon their separation may be sutured in their entirety, as
individual nerves. When a nerve
trunk is found to present evidence of almost complete anatomic
division, retaining only a small
degree of functional integrity, one is justified in resecting the
entire trunk and effecting a
complete suture, but all partial lesions retaining important functional
integrity should be
subjected to individual bundle examination and repair.
COMPRESSION
AND
STRANGULATION LESIONS
Nerve
trunks, while retaining their anatomic continuity, may be compressed to
such a
degree as to interrupt their physiologic continuity. This compression,
972
if excessive,
may result in complete strangulation with neuraxon degeneration.
Strangulative lesions with degeneration (do not present the typical
neuroma, as is common to
anatomic divisions, and the nerve can usually be traced through scar
tissue as a more or less
intact anatomic structure. Nerves may be compressed by extraneural scar
tissue, bone callous, or
even external pressure, such as ill-fitting splints, crutches, or the
edge of operating tables. Surgical intervention is not indicated in the
milder degrees of compression until sufficient time
has elapsed for evidence of spontaneous regeneration. When, however,
after three months there
exists no sign of regeneration and the exact location of the lesion is
known, the surgeon is
justified in exploration. While extraneural lesions are probably the
most common cause of nerve
compression, two other types often exist which far more frequently
demand surgical intervention: Compression or strangulation from nerve
sheath involvement, and intraneural fibrosis.
NEUROLYSIS
Many
surgeons have been content with an external neurolysis when exposure
revealed the nerve trunk to be anatomically intact; such a procedure
has frequently given very disappointing end results, obviously,
because of inadequate bundle decompression. When a
FIG.
163.- A, Physiologic
interruption of a
nerve; nerves with this appearance are occasionally considered as
having
an "internal neuroma." B, Showing the enlargement to be due to a
greatly posed and surrounding scar thickened
nerve sheath, producing compression or strangulation. C, Perifunicular
adhesions following the prolonged use of a
tourniquet. The method of separation of adhesions, as in A and B. The
sheath is left open to prevent future
strangulation, and the exposed funiculi are protected by adjacent fatty
tissues when present, or fat transplantation.
(Ney. Annals of Surgery, 1921)
compression lesion has
been exposed and surrounding scar tissue removed (which constitutes an
external neurolysis), the nerve trunk should be carefully palpated; if
it be found soft, without
evidence of a thickened sheath or intraneural fibrosis, the external
neurolysis should be deemed
sufficient.
When
the nerve has an indurated appearance and presents undue hardness on
palpation,
decompression, or internal neurolysis is indicated. The nerve sheath is
longitudinally incised,
exposing the indurated portion, and gently held open with fine traction
sutures or mosquito
forceps. This intraneural exposure will usually reveal the nature of
the compression, whether it
be due to a thickened indurated nerve sheath or to an intraneural
fibrosis. When the compression is confined to a thickened and indurated
nerve sheath, the exposed bundles, though
showing signs of compression, will be found intact, readily
973
isolated, and free from
scar tissue. Such a condition is usually relieved by the simple
decompressive procedure of opening the nerve sheath. When the sheath
exhibits marked
thickening the thickened portion may be resected, no attempt being made
at closure. Occasionally
the intraneural exposure reveals" matting" of the bundles by adhesions;
intraneural neurolysis is
then indicated. The bundles are gently dissected free from the scar
tissue by inserting the blades
of fine-pointed iris scissors which are spread, gently separating the
bundles from the
perifunicular adhesions. If, however, the bundles are found imbedded in
a dense mass of scar in
which they lose their anatomic identity, resection of this area is
indicated, and the nerve united
according to the usual technique for end-to-end suture.
THE ELECTRICAL EXAMINATION OF NERVES AT OPERATION
Important
information may be obtained by the routine use of faradic stimulation
of nerves
when exposed at operation. The battery required is the ordinary type of
single-cell faradic
medical battery, in which the strength of current may be regulated by
moving the core. A fine-pointed bipolar electrode is connected to the
battery with plain copper or silver wires, which may
be sterilized by boiling. Small glass beads may be threaded on each
wire to prevent short
circuiting. Ordinarily the bare ends of the wire may be used as a
bipolar electrode, but for the
more delicate procedure of funicular identification needle points
should be used, these points
having a separation at their end of approximately 2 mm. In beginning
the test the weakest
possible current should be used, the strength of which may be increased
as desired, by the
attendant manipulating the coil. The operator should assure himself
that the connections are
intact and the battery is working properly, by stimulating neighboring
exposed muscular tissue
whose nerve supply is normal.
When
a compressed nerve is exposed at operation. it should be stimulated
both above and
below the lesion. If weak faradic stimulation above the lesion gives a
response in the paralyzed
muscles, it is doubtful whether the lesion exposed is responsible for
any serious compression.
Where such a condition is found to exist before the nerve has been
decompressed, the diagnosis
of an organic lesion is questionable, providing all the muscles respond
to stimulation. It is
possible, however, that the surgeon is dealing with a partial lesion
and is stimulating intact fibers.
A careful preoperative examination, however, should have demonstrated
the probability of such a
condition. Occasionally, an anatomically intact nerve may be exposed in
a compression lesion,
where stimulation above the lesion fails to elicit a response, while
stimulation below the lesion
gives definite muscular contractions; such findings are found only in
the mildest grades of nerve
compression, and a careful neurolysis will usually result in the
passage of electrically excited
impulses beyond the lesion, providing the nerve has not been
traumatized nor stretched during
the neurolysis. Trauma during neurolysis will frequently cause the
disappearance of the electrical
conductivity previously found.
974
ELECTRICAL IDENTIFICATION OF PHYSIOLOGIC
COMPONENTS OF A DIVIDED NERVE
When
a nerve is exposed under local infiltration anesthesia and before the
nerve trunk has
been anesthetized, it is possible by opening the nerve sheath of the
upper segment to effect
physiologic identification of the exposed bundles by weak faradic
stimulation. The stimulation of
a sensory bundle elicits a tingling sensation localized in the normal
cutaneous sensory area of
that nerve; if the stimulation is too intense, considerable pain may be
experienced. Stimulation
of a motor bundle is not associated with pain unless the current is
diffused to sensory bundles.
The stimulation of myosensory fibers, usually found in a motor bundle
below a nerve plexus,
gives a sensation of muscular action. (See technique of
electro-anatomic funicular identification
p. 963.) In partial lesions of nerves the physiologic intact portion of
the nerve trunk may be
determined by faradic stimulation.
The
success of electrical identification of nerve bundles depends primarily
upon an
extremely careful and gentle technique. If the current used is a bit
too strong, the patient is caused
pain and the tests are difficult to control. The current also has a
tendency to diffuse throughout
the nerve trunk, stimulating all fibers and rendering the test
valueless. When carefully and accurately applied it is an extremely
valuable adjunct in identifying the physiologic components of a
nerve trunk. In long-existing paralysis the stimulation of motor
bundles will occasionally give no
myosensory reaction; the same istrue in the stimulation of motor
bundles above a nerve plexus.
The most reliable results obtained are from stimulating a completely
formed branch, before it has
left the parent trunk.
SECONDARY OPERATIONS FOR DEFECTIVE REGENERATION
Inasmuch
as defective regeneration may take place in both nerve and muscle, it
is
essential in the absence of regeneration to decide definitely the
nature of the regenerative defect.
MUSCLE REGENERATION
Primarily,
degeneration in paralyzed muscles following peripheral nerve injuries
is due to
denervation; the longer a muscle remains denervated the more intense
will the degenerative
changes become. In muscles of small size these degenerative changes
seem to become extreme,
and after a period of 12 or 18 months the degeneration has progressed
to a point where recovery
is extremely doubtful. Small muscles, like the intrinsic muscles of the
hand and foot, being
innervated at a great distance, seldom recover after nerve injury if
deprived of their nerve supply
longer than one year. Therefore, secondary operations are, as a rule,
not indicated for
regenerative failure in muscles of small size with distal innervation.
In muscles of larger bulk,
whose nerve supply is usually derived at a higher level, the chances
for regeneration are far more
favorable; in regeneration of the injured nerve they receive nerve
fibers much earlier than the
smaller, more distally located muscles, and
975
their larger bulk
insures their receiving a greater number of regenerated motor fibers.
In the upper
extremity regeneration occurs in about the same degree in muscles of
comparative size, whether
they be innervated by the musculospiral, median, or ulnar nerves,
providing the lesion of these
respective nerves occurs at about the same level and the period of
their denervation is the same.
In brachial plexus lesions, which are high lesions, the more distal
muscles in the forearm, as a
rule, show more extreme degeneration and less tendency to recover than
those muscles deriving a
higher innervation. In high sciatic trunk lesions recovery of the
gastrocnemius is much more
likely, because of its large bulk and comparatively high innervation,
than is to be expected in the
flexors or extensors of the toes. We may conclude, therefore, from a
standpoint of muscle
regeneration, that the longer a muscle remains paralyzed the greater
will be its degeneration and
the less likely will be motor recovery.
Reoperation
on nerve trunks is indicated solely because of absent or defective
neuraxon
regeneration, and not because of defective muscle regeneration. While
re-innervation is
absolutely essential to muscle regeneration, it must be remembered that
muscular tissue having
undergone extreme degrees of atrophy will not regenerate to a degree of
functional usefulness
when reinnervated. It must also be remembered that defective
regeneration frequently occurs in
muscles which have undergone prolonged overstretching; also that
muscles showing signs of
regenerative changes may be late in responding to voluntary motor
impulses, due to concomitant
functional conditions and lack of reeducation. A muscle showing signs
of increasing electrical
and mechanical irritability is undoubtedly regenerating; a muscle
completely devoid of electrical
and mechanical irritability either has undergone complete degeneration,
resulting in a fibrous
transformation, or else it remains denervated.
NEURAXON REGENERATION
Neuraxon
regeneration in its early stages may be determined only by Tinel's sign
of
formication. Regeneration, following suture of a peripheral nerve,
occurs after the first month at
the rate of about 3 cm. per month, providing regeneration is unimpeded.
After the third month,
formication should be elicited in the lower segment of the nerve; at
the end of six months, it
should he elicited 5 or 6 inches below the suture line with about the
same intensity as the reaction
obtained at the suture line. While this reaction gives evidence only of
sensory fiber regeneration,
it is probable that motor fibers contained in the same sheath have
regenerated to the same degree.
Tinel's sign is the only means we have at our disposal at the present
time for determining
neuraxon regeneration, until the regenerating motor and sensory fibers
have reached their
respective terminations and manifested their presence by a return of
sensation and muscle
regeneration. The absence of Tinel's sign in the distal segment of a
sutured mixed peripheral
nerve, after four to six months, definitely indicates an absence of
neuraxon regeneration,
providing this sign may be elicited with intensity at the suture line.
When Tinel's reaction in the
lower segment of the nerve is of considerably less intensity than at
the suture line, defective
regeneration may be definitely concluded. The state of a negative,
976
or seriously defective
neuraxon regeneration calls definitely for surgical intervention.
In
certain instances. neuraxon regeneration may progress favorably down
the distal
segment of the repaired nerve without restoration of motor or sensory
function, due to torsion of
the nerve trunk during suture, with misdirection of fibers, resulting
in their complete physiologic
loss. This accident may occur to any degree, and doubtless many
defective regenerative results
are due primarily to this cause. We may, in general, classify
regenerative failure into three
groups: (1) Absent or defective neuraxon regeneration; (2) defective
regeneration, due to
disturbance of nerve pattern during primary suture;(3) persistence of
muscle degeneration after
reinnervation.
1.
The factors responsible for absent or defective neuraxon regeneration
will usually be
found at the suture line. They are:
a.
Defective approximation, in which the proximal segment of the nerve
presents a
secondary neuroma which calls for resection and accurate approximation.
b.
Construction in the region of the primary suture by a scar infiltrated
nerve sheath not
sufficiently resected at the primary operation, which calls for
decompression. The surgeon should
assure himself that the exposed intraneural contents are not subject to
extensive scar invasion; if
such be the case, complete resection and a new approximation will be
indicated. If the intraneural
contents are found to be soft to palpation without evidence of scar
infiltration, the defect should
be considered as having been corrected by the decompression.
c.
Construction by perineural scar tissue is usually the result of
excessive tissue trauma,
defective hemostasis, or infection following suture. Occasionally the
failure to provide a suitable
bed for the repaired nerve may be responsible; this obstruction to
regeneration sometimes
follows the use of foreign tissue, which at one time was used
extensively to protect the suture
line. Undoubtedly, experience has shown that the best protection a
nerve may have is its own
sheath; that an excess of scar tissue subsequent to operation can
usually be avoided by paying
due respect to the above enumerated causes. After the nerve trunk has
been freed from
constrictive extraneural scar tissue and found to be free from
intraneural scar invasion, it should
be transposed to a new and more favorable bed.
2.
Defective regeneration, due to torsion of the nerve trunk during the
original suture,
calls for resection of the original suture line and reapproximation; in
this, the surgeon must resort
to topographical identification, which is considered in detail under
the surgery of individual
nerves.
3.
Failure of muscle regeneration does not call for surgical intervention,
in so far as the
nerve is concerned. When the degenerated condition of the muscles has
persisted for two or three
years following a nerve suture with successful neuraxon regeneration,
they should be considered
as irretrievable lost and recourse should be taken to such
supplementary procedures as will assist
in correcting the defect. (See irreparable lesions of special nerves,
p. 959.)
977
TENDON TRANSPLANTATION
Tendon
transplantation, in peripheral nerve lesions, is indicated for the
correction of
defective motor regeneration, whatever may be its cause. It should not
be resorted to, particularly
when it entails a sacrifice of muscles and tendons, as most transplants
do, until the persistence of
the motor defect is definitely established or the extent of the nerve
injury precludes the possibility of repair. Two exceptions to this rule
at the present time are
pronator teres transplantation
for extension of the wrist, and the author's transplant for restoring
opponens function to the
thumb; both of these procedures may he executed without jeopardizing
subsequent muscle
regeneration or interfering with muscle action after regeneration. In
fact, both procedures,
particularly the latter, tend to relax the paralyzed muscles, making
conditions more favorable for
their regeneration. In irretrievable lesions of a peripheral nature,
tendon transplantation offers a
very valuable means of restoring, to some extent at least, movements
lost by the original
paralysis.
The
general principles governing tendon transplantation are primarily the
same in both
upper and lower extremities, though the chief desideratum in the upper
extremity is mobility,
while in the lower extremity stability for weight bearing is more
essential. To hope for successful
functional end results following tendon transplantation, the surgeon
must adhere strictly to
certain general principles which experience has proved to be
indispensable; the neglect of these
primary requisites is but to invite failure, following which the after
results mav be more
unsatisfactory than the former.
An
important essential to the success of tendon transplantation lies in
the mobility of
those joints upon which the transplanted tendons act. A joint whose
function is fixed in
deformity will never respond to the action of transplanted tendons.
Before tendon transplantation
of any type is attempted, the surgeon should assure himself that the
range of motion in these
joints which are to be influenced by the transplantation must be fully
adequate to functional
needs and without restriction. An operation for tendon transplantation,
therefore, must be
definitely postponed until restricted joints are fully mobilized and
tendon and fascial contractures
completely corrected.
For
restoration of function through tendon transplantation, only muscles
with sufficient
power and contractile vigor should be used. It is therefore essential
that the surgeon be familiar
with the ways and means of determining individual muscle function, and
in the selection of a
muscle for transplantation, its ability to do the proposed work should
be definitely determined. A
normally weak muscle should never be expected to assume a function
requiring greater power
than it ordinarily possesses. Though a muscle may hypertrophy, to a
certain extent, to assume an
additional burden, its power to do so is markedly limited and should
not be too greatly relied
upon.
While
various rules have been promulgated from time to time, on the grounds
of
synergetic action, for the selection of muscles to be used in tendon
transplantation, practical
experience has demonstrated that certain deviations from these rules
have been attended with
considerable success. It is important, however, in selecting a muscle
for the performance of a
specific function that
978
it be adapted
physiologically to that function. Although it is generally held that an
antagonist
should never be selected for tendon transplantation, it should be
remembered that anatomic
antagonists may not, in a strict sense, be physiologic antagonists. In
the synergetic action of
muscles, for the accomplishment of smoothly adjusted movements, a
contraction in a certain
group of muscles will call into play a relaxation of a physiologic
antagonistic group. In the
execution of certain other movements, however, a muscle anatomically
antagonistic may contract
simultaneously with its opponent, to fix a joint in a position which
will supplement the action of
the other muscles.
The
determination of synergetic action in various movements is extremely
complicated
and can be comprehended only after a careful study of individual and
combined muscle action.
The surgeon is materially assisted, however, in the determination of
those muscles of separate
innervation, which contract simultaneously for the execution of a given
movement, by the study
of "trick or substitution" movements commonly seen in peripheral nerve
injuries.
The
maintenance of direct muscle pull from origin to insertion should be
assured in
tendon transplantation by long incisions and adequate tendon and muscle
mobilization. A muscle
with an obliquity of pull is much less effective than one pulling in a
direct line. In the
transplantation of tendons, therefore, free tendon mobilization and the
avoidance of angulation
are primary requisites.
The
tunnel best adapted to transplanting is one directed beneath the fat of
the superficial
fascia, where adhesions are less apt to be dense. It is advisable, in
planting the original incision,
to avoid if possible the superimposing of skin and tendon sutures. The
amount of tension exerted
upon a transposed tendon is frequently responsible for success or
failure. A muscle is an elastic
structure and its inherent elasticity and tone will cause shortening
when its tendon is divided. In
making an anastomosis, it should be held sufficiently taut to restore
its normal tension, but must
in no wise undergo a degree of stretching sufficient to produce a
paresis. The joint to be acted
upon must be flexed or extended to the degree to which the transplanted
tendon is expected to
act. If it is desired to procure complete extension of hand and
fingers, they must be so maintained, in extension, during
approximation of the tendon, and the anastomos is effected under
sufficient tension, that when the anastomosis is completed and the
muscle completely relaxed, it
still is under a degree of tension comparable to that existing in the
muscle previous to its
transplantation.
After
suture, the member must be maintained continuously in the position
under which it
was placed during transplatation, lest the sutures in the anastomosed
tendon be avulsed or
broken. This requires considerable care and attention on the part of
the assistant during closure of
the integument and the application of dressings. It is usually
advisable to prepare a suitably
moulded splint in advance, in order that it may be slipped into
position without delay and without
jeopardizing the anastomosis. In the preoperative preparation of the
splint, it should be moulded
to maintain exactly that position which the tendon transplant is
expected to effect during its
maxi-mum action; however, the joints involved should not be
sufficiently extended
979
or flexed to produce
discomfort. The splint should be so arranged that removal of dressings
is
possible without disturbing the position of the extremity.
After
the second week, passive movements may be instituted to prevent joint
restriction,
and to stretch the adhesions about the anastomosis before fixation
occurs. These active and
passive movements must be executed with extreme care, and controlled by
one who is familiar
with the nature of the operation and experienced in the treatment of
these conditions. If healing
of the skin is complete, gentle massage of the extremity may now be
practiced.
After
a period of one month the splint may be entirely removed during
treatment, after
which it is replaced. Two weeks later, the splint may be removed for a
short time each day, which
period may be lengthened as the transplanted muscles develop in
strength. If after discarding the
splint the muscles seem to become weaker, it should again be applied
and worn continuously for
a few weeks. A night splint is important and should be worn for a
period of at least two months
following the discarding of the day splint.
Reeducation
consists in explaining to the patient the nature of the operation,
demonstrating the original action of each muscle, and then the acquired
action through tendon
transplantation. It has been the writer's practice to have the patient
instructed before the operation
in the individual use of those muscles which will be used in
transplantation. Frequently the use of
electricity will demonstrate to a patient more clearly than any other
means the action of his
transplanted muscle. The progress in reeducation depends less upon the
individual than upon the
nature of his instruction. It is expedient that the surgeon keep these
patients under his personal
supervision until such a time as the ability is acquired to use his
transplanted tendon properly.
Three
months is usually required for the scar tissue, uniting the tendons, to
become
sufficiently hard to resist the strain of ordinary functional demand,
and until this period has
elapsed care should be used in preventing any undue strain falling upon
the transplanted tendons.
INFECTED WOUNDS AND NERVE SURGERY
It
is folly to attempt nerve repair in the presence of an infection or an
open wound, and if
during the course of a dissection pus is uncovered in bone or soft
tissue, the attention should be
directed to the removal of the infected area, and the nerve repair
postponed until the infection is
completely controlled and the wound entirely healed.
RECRUDESCENCE OF INFECTION IN CICATRIZED WOUNDS
Frequently
our attention has been attracted to the recrudescence of an infection
in wounds
which have for many months been completely cicatrized. Wounds which
have undergone a long
period of suppuration may harbor latent infection for months or even
years following their
cicatrization, and during this period any form of tissue trauma,
surgical or otherwise, may serve
to initiate a recrudescence of the latent infection, which may be
attended with high temperature,
great pain, and all the symptoms of a local or even a general sepsis.
It is essential, therefore, that
a sufficient period of time be allowed to elapse following the healing
of an infected wound to
insure to some degree the
980
safety of a surgical
invasion. When suppuration has attended the healing of a wound
involving
only soft parts, an aseptic surgical operation in the vicinity of this
wound should not be attempted
until cicatrization has been complete for a period of at least three
months. When the suppurative
process has involved osseous structures, the period of waiting should
be prolonged to at least six
months, and in many instances the operation will not be safe for a
period of one year, particularly
if there is a history of repeated breaking down of the wound. Inasmuch
as this attitude of
conservatism or watchful waiting may jeopardize the ultimate outcome of
nerve repair, because
of delayed intervention, a more active policy may be pursued for the
clearing up of scars
suspected of harboring infection.
We
have satisfactorily used the following method of testing for latent
infection: For two
days previous to the test the patient is confined to bed and his
temperature recorded every four
hours, a leucocytic count having been made on two alternate days. The
scar is then subjected to
vigorous massage for a period of five minutes. Following this, for one
week the four-hour
temperature is recorded and daily leucocytic counts continued. Careful
daily inspection of the
wound is made for local signs of inflammation, such as swelling,
redness, or increased local
temperature. A wound harboring infection will usually reveal its
presence by both a local and a
general reaction. An elevation of temperature, an increased
leucocytosis, or signs of a local
inflammatory nature will usually be observed if there be a dormant
infection. If no reaction be
elicited, it may be considered safe to attempt a clean operation; if,
however, a reaction does occur
following the massive massage, excision of the scar tissue followed by
wound sterilization and
closure should be attempted, and the nerve operation delayed until this
wound has been
completely healed for a period of three months.
PRIMARY OPERATIONS
There
can be no doubt regarding the advantage of immediate nerve suture
following
wounds in which, during examination, the nerve is found to be
completely divided. Inasmuch as
most lacerated wounds are infected, the question naturally resolves
itself into a discussion of the
advantages and disadvantages of suturing a nerve in the presence of
infection, or where infection
seems inevitable. Before the days of wound excision and successful
sterilization, one could not
suture a nerve and hope for satisfactory regeneration to any degree.
If
wound excision and sterilization seem probable, the surgeon is
justified in
approximating the ends of the nerve with fine sutures, or even by a
single tension suture, with the
primary object of preventing retraction and fixation of the nerve ends,
thereby diminishing the
extent of the continuity defect during the process of healing and
perhaps making less difficult a
secondary operation. In any wound potentially infected, the excision of
nerve ends and the
extensive exposure necessary to satisfactory approximation should be
vigorously discouraged, as
this procedure invariably opens up new channels for infection, is
rarely successful, and greatly
complicates the almost inevitable secondary suture. It is therefore
advisable in all open wounds,
complicated by nerve injury, to first control infections, delaying the
operation for nerve repair
until such a time as it may be aseptically accomplished.
981
NERVE INJURY
DURING DÉBRIDEMENT
The
efficacy of wound débridement has become established. In the hands of
the skilled
and experienced surgeon, d bridement with primary suture has in many
instances resulted in
primary healing, but in the hands of a novice it is a procedure nothing
less than hazardous. There
can be little doubt that many nerves receive their first injury from
the scalpel of the surgeon
during débridement. The writer, on one occasion, witnessed the excision
of 2 inches of the
musculospiral nerve, during a spectacular débridement of a gunshot
wound.
Every
injured extremity, having undergone débridement or any other operative
procedure
subsequently revealing a nerve injury, casts serious reflection on the
operating surgeon, if the
preoperative record fails to record the presence of that nerve lesion.
The ease and rapidity with
which an injured extremity may be examined for the presence of a
complicating nerve injury
leaves no excuse for its oversight in the preoperative records; a later
discovery certainly throws
the burden of responsibility upon the operator.
AMPUTATION NEUROMAS
The
development of a neuroma at the end of a nerve, particularly when the
neuroma is
incorporated within the scar of an amputation stump, may cause extreme
discomfort or pain,
which is intensified by the pressure of amputation prosthetic
appliances. To prevent subsequent
annoyance of a painful amputation neuroma, the nerve, at the time of
amputation, should be withdrawn and resected
at as high a level as possible and injected with 80 per cent or
absolute
alcohol. If a nerve is not injected with alcohol, a neuroma will
invariably form, but if the
neuroma is located some distance above the cicatricial tissue of the
stump, it is seldom subjected
to irritation.
TREATMENT
A
neuroma incorporated in the scar tissue of a stump usually calls for
removal, with high
section of the nerve. Frequently it is not considered advisable nor
desirable to increase the scar of
the stump by an additional incision; in such instances the nerve
involved may be exposed some
distance above the neuroma, injected with alcohol and sectioned. This
procedure is quite as
satisfactory as the removal of the neuroma, as it permits degeneration
of its contained nerve
fibers. Occasionally, the surgeon may resort to a plastic procedure on
the larger nerves to prevent
the formation of a subsequent neuroma.(See fig. 164.)
It
is essential in each instance to determine the nerve responsible for
the irritation.
Pressure or percussion in the painful region will usually elicit
tingling, which is localized in the
cutaneous area normally supplied by that nerve. For example, if after
an amputation of the arm a
painful neuroma develops in the stump, and percussion of that neuroma
elicits tingling localized
in the little finger, the surgeon will know that the neuroma is of the
ulnar nerve; if it is located in
the second or third fingers, the median nerve will require resection.
It is important to accurately
determine the nerve responsible for
982
the pain. The writer has
on several occasions seen a persistence of pain after neuroma removal,
obviously because there were several neuromas in the stumpand the
neuroma responsible for the
painful syndrome was unfortunately missed, a proper localization
evidently not having been
made.
FIG. 164.- Plastic
procedures and alcoholic injection to prevent the formation of
amputation
neuromas
THE
BRACHIAL PLEXUS
GENERAL ANATOMY
The
brachial plexus is formed by the anterior primary divisions of the
fifth, sixth, seventh,
and eighth cervical and first thoracic nerves, located in the posterior
triangle of the neck and in
the axilla. While the brachial plexus varies often in its formation, in
that the fourth cervical nerve
and the first thoracic may give a greater or lesser number of fibers to
its formation, its general
anatomy is fairly constant. Minor variations in the origin of branches
will occasionally be found,
but these anomalies are not sufficiently great to modify the surgical
principles involved in
attempting physiologic reconstruction of the plexus.
The
plexus first consists of three primary trunks, lying upon the scalenus
medius muscle;
the upper trunk is formed by the fifth and sixth cervical nerves, the
middle trunk by the seventh
cervical, and the lower trunk by a
983
union of the eighth cervical and first thoracic nerves. Each of these
primary trunks subsequently
divide into an anterior and posterior division, which ultimately form
the three plexus cords. The
anterior divisions of the upper and middle trunk form the outer cord,
which terminates by
dividing into two branches, the musculocutaneous and the outer head of
the median. The anterior
division of the lower trunk forms the inner cord, which ultimately
breaks up to form the inner
head of the median, the ulnar, and the greater and lesser internal
cutaneous nerves. The posterior
divisions of the three primary trunks unite to form the posterior cord
of the plexus, which
terminates by dividing into the circumflex and musculospiral nerves. In
the region of the clavicle,
the three primary trunks divide into their anterior and posterior
divisions, which are often
comparatively short and lie lateral to the subclavian artery in close
relation to the apex of the
lung. Just below the clavicle, the anterior and posterior divisions of
the primary trunks arrange
themselves into the three plexus cords, which surround the axillary
artery in its second portion,
the outer cord lying upon the outer side of that vessel; the inner cord
on its inner side; and the
posterior cord behind. In the region of the coracoid process of the
scapula, these cords divide into
their terminal branches to supply the musculature of the arm and
provide sensation to its
integument.
A
number of branches are given off from the brachial plexus to muscles of
the shoulder
girdle; the course of most of these is relatively short and they do not
often lend themselves
readily to surgical repair. Attention, however, must be directed to
some of the larger and more
important branches, which must be recognized and preserved in the
surgical reconstruction of the
plexus.
The long or posterior thoracic nerve usually arises by three roots
from the fifth, sixth,
and seventh cervical nerves, close to the intervertebral foramina. This
nerve is very long and
passes down behind the brachial plexus and axillary vessels along the
outer surface of the
serratus magnus muscle, which it supplies.
The suprascapular nerve arises from the lateral border of the upper
trunk and passing
obliquely outward beneath the trapezius and omohyoid, supplies the
supraspinatus and
infraspinatus muscles. In the dissection of the upper trunk, the
suprascapular nerve should be
identified and carefully preserved, or individually sutured if
necessary, to preserve or restore
function in the spinatus muscles; this is particularly important in
deltoid paralysis.
The subscapular nerves, usually three in number, arise from the
posterior cord below the
clavicle and supply the subscapularis, teres major, and latissimus
dorsi muscles. The importance
of preserving these branches is obvious in the presence of a deltoid
paralysis.
The anterior thoracic nerves are two in number and supply the
pectoral muscles. The
external and larger of the two arises from the outer cord of the plexus
and passing inward crosses
the axillary artery and vein, where it is distributed to the under
surface of the pectoralis major.
The inner anterior thoracic nerve arises from the inner cord and
passing behind the axillary
artery, it curves forward between the axillary artery and vein to the
undersurface of the pectoralis
minor. Anterior to the axillary artery, the external and internal
thoracic nerves are commonly
united by a filament from the external nerve.
984
It
should be remembered, therefore, in the dissection of the brachial
plexus that in
exposure of the upper trunk, the suprascapular nerve must be identified
and preserved. In
dissection of the posterior cord, the subscapular nerves require the
same consideration, and in the
dissection of the outer and inner cords, the external and internal
anterior thoracics should be
identified and preserved to retain pectoral function. The thoracic
nerves are particularly liable to
injury during dissection and isolation of the axillary vessels; their
early identification during this
procedure is important.
SURGERY
Traumatic
lesions of the brachial plexus are fairly common in both civil and
military life.
The nature of these injuries may be direct, in which portions of the
plexus are involved by
penetrating wounds; or indirect, which are due more frequently to
stretching of the plexus, the
mechanism of which consists in forcibly depressing the shoulder while
the neck and head are
forced to the opposite side, greatly increasing the shoulder and neck
angle. Indirect injury may
result in lesions of varying degree, and in severe cases roots may be
completely avulsed from the
spinal cord. The avulsion more commonly takes place just external to
the intervertebral foramina
and often is confined to the upper roots of the plexus. Not
infrequently, such injuries are limited
to an overstretching of the upper trunk, which may or may not cause
rupture of its intraneural
constituents, the entire nerve sheath usually remaining intact. In such
lesions spontaneous
regeneration will probably occur under appropriate splinting and
relaxation treatment. There are,
however, certain anatomic factors in this region which tend to inhibit
spontaneous regeneration.
The brachial plexus is closely covered by the prevertebral layer of the
deep cervical fascia, and
indirect lesions of the plexus, with or without rupture, are often
attended with hemorrhage under
the fascia layer, which may be responsible for primary compression and
ultimate more or less
dense scar formation. These adhesions between the plexus and the
prevertebral fascia are the
most conspicuous features of the lesion, which upon exposure presents
itself as a mass of scar
tissue. It is usually only after careful sharp dissection of this
fascia from the plexus that it is
possible to proceed with identification of the individual anatomic
plexus constituents, and not
infrequently a thorough neurolysis of the plexus will be all that is
required. While lesions of the
upper trunk and outer cord are more common following indirect injury
from stretching, lesions of
the lower portion of the plexus more often result from direct trauma.
The proximity of the lower
plexus to the apex of the lung and important vascular channels makes
penetrating wounds in this
region particularly serious, frequently leading to an early fatal
termination from hemorrhage. The
relation of the trunk of the brachial plexus to the axillary artery is
responsible for many combined
lesions in which hematoma and subsequent scar tissue simultaneously
compress the nerve trunks
and vascular structures, combining ischemia with compression paralysis
and often resulting in
painful paralytic syndromes. Aneurysm is not an uncommon complication
in lower plexus
penetrating wounds. The relationship of the lower trunk of the plexus
985
to the first rib and the
pleura are likewise anatomic conditions peculiar to the plexus, often
greatly complicating the nerve lesion.
Exact
anatomic knowledge and adequate exposure are essential in nerve
surgery,
regardless of the location; in the surgery of the brachial plexus these
primary requisites are
indispensable. At best, the end results of severe brachial plexus
lesions are disappointing.
Manifestly, many of these severe lesions are practically hopeless from
a surgical standpoint, due
to the fact that the lesion lies within or closely approximating the
intervertebral foramina. It is
well that the surgeon appreciate the technical difficulties which at
present limit anatomic
reconstruction in lesions involving the roots within or proximal to the
intervertebral foramina.
Plexus injuries associated with avulsion of the roots within the spinal
canal are usually
associated with some cord involvement, which will be evident on a
systematic neurologic
examination. Lesions within the intervertebral foramina will usually
involve both anterior and posterior divisions of the cervical nerves,
which will be evidenced by the addition of a dorsal
anesthesia in the cervical region corresponding to the dorsal rami of
the cervical nerves. The
motor branches contained in the dorsal rami are distributed in a manner
which does not readily
lend itself to this differentiation; however, the sensory impairment
referred to should place the involvement within the intervertebral
foramina. The presence of a paralysis of the serratus
magnus innervated through the long thoracic nerve whose branches are
given off from the
anterior divisions of the fifth, sixth, and seventh cervical nerves
close to the intervertebral
foramina will indicate a lesion in this location, particularly if the
rhomboids are found to be
involved. Therefore (1) brachial plexus lesions associated with spinal
cord involvement usually preclude the possibility of repair; (2)
lesions associated with a dorsal area of anesthesia
corresponding to the dorsal cervical divisions likewise preclude the
possibility of repair, due to
involvement within the intervertebral foramina; (3) lesions associated
with paralysis of the
serratus magnus and rhomboids make extremely doubtful the possibility
of repair, due to the
proximity of the injury to the intervertebral foramina; (4) plexus
lesions associated with sym- pathetic involvement (Horner's
syndrome-myosis, enophthalmus, and narrowed palpebral fissure)
indicate a lesion involving the eighth cervical nerve within or
immediately adjacent to the
intervertebral foramen, which greatly diminishes the possibility of
repair in this region.
While
the presence of the above types of brachial plexus lesions usually
precludes the
possibility of repair, the surgeon may feel the desirability of giving
the patient the benefit of any
doubt; the justification of assuming the risk of along, tedious
exposure is found in the fact that in
the hands of an experienced neurologic surgeon there is little chance
of increasing the disability
and there may be a possibility of reconstructing some portion of the
plexus. However, upon
exposure, if the surgeon is content with simply approximating nerves,
without regard to original
physiologic pattern, even though the operation be followed by a
regeneration of nerve fibers, the
physiologic outcome will be such a distortion of motor and sensory
function, as to exclude any
possibility of usefulness in the extremity. The writer has seen several
instances of brachial plexus
lesions, following suture, in which neuraxon regeneration was active,
986
but with distortion of
nerve pattern, resulting in most perplexing combinations of motor
response
and sensory localization. At least in the repair of the brachial
plexus, the surgeon should by all
means endeavor to approximate corresponding roots, trunks, and terminal
branches, though even
when this is accomplished and regeneration of nerve fibers is
successful, it will be found that if
there has been a torsion of the nerve trunk during suture, the ultimate
physiologic outcome in that
particular trunk will be more or less defective.
These
facts will serve to partially explain the many instances in which
sutures of the
brachial plexus have been attended with such poor functional results.
In order to avoid these
unsatisfactory terminal results, the surgeon should fortify himself
with such degree of anatomic
and physiologic familiarity with the brachial plexus as will permit
him, during repair, to
conserve, as much as possible, its original pattern. If the surgeon
feels that he is not sufficiently
familiar with the intrinsic plexus anatomy to practice physiologic
reconstruction, he had better
confine his efforts strictly to a careful and painstaking
neurolysis--which conservative attitude, in
all probability, in the great majority of cases, will be attended with
a more satisfactory functional
end result. When, however, there has been an actual division of a
portion of the plexus, its repair
should be conducted with all precautions toward the prevention of
distortion of the nerve pattern,
by eliminating torsion during suture.
Most
direct lesions involving the brachial plexus above the clavicle result
in injury to the
primary trunks, or their anterior or posterior divisions, while lesions
below the clavicle usually
involve the cords or their terminal branches. Penetrating wounds seldom
involve the entire
plexus, and it is usually possible, by careful preoperative examination
of individual muscle
function, to determine the exact location of the lesion. The surgeon so
armed with a precise
knowledge of plexus anatomy and clinical localization, will be able,
after identification of the
various intact branches by faradic stimulation, to definitely locate
the lesion. This having been
accomplished, should complete division be found, he will be able to
effect reconstructive suture
by uniting respective trunks without torsion with the aid of
identification sutures and branch
identification. For example, if the lesion compromises the terminal
portion of the inner cord,
involving the inner head of the median, ulnar, and internal cutaneous,
the relative position in
reconstructive suture would be: The inner cord of the median to the
upper or lateral part of the
anterior division of the lower trunk; the internal cutaneous would
occupy the lower and medial
side of the trunk; the ulnar, the center of the trunk between the inner
head of the median and the
internal cutaneous. To prevent torsion of the proximal segment, the
position of the eighth
cervical nerve would indicate the upper or lateral portion of the root;
the position of the first
thoracic, the lower portion of the root; and the posterior division,
its posterior surface. This
type of anatomic reconstruction during suture, while by no means
perfect, in that shunting of
fibers is still possible in the terminal segments, will promise the
highest degree of efficiency
compatible with our present knowledge of ways and means to preserve
intraneural topography.
While this is purely an anatomic method, a careful study of the nerve
trunk, its formation, the
987
position of terminal
branches, etc., will usually serve to prevent serious torsion. The
writer finds
that the use of an enlarged anatomic chart in a convenient position in
the operating room is of
great service in assisting the visualization of reconstructive
requirements in the surgery of
brachial plexus lesions. The chart should indicate the respective
muscles innervated by each
primary, secondary, and terminal division of the plexus, so that in
electrical stimulation,
precision in identification may be facilitated. It is needless to state
at this point that in preparing
the field for operation the entire arm should be included, in order
that it may be properly exposed
and manipulated for inspection of muscle action during electrical
stimulation of nerve trunks and
branches.
TECHNIQUE OF EXPOSURE
The
patient is placed upon his back with head abducted and rotated to
opposite side, and
shoulder depressed; a sand bag placed between the shoulders is often of
value in maintaining this
position. A "step-shaped" incision has been found the most desirable
for complete exposure of
the plexus. The upper longitudinal limb of the incision parallels the
posterior border of the
sternomastoid muscle to a point just below the clavicle; turning
outward, the incision transverses
the thorax along the lower border of the clavicle to the junction of
its outer and middle third;
from this point it passes down over the anterior aspect of the shoulder
to the medial side of the
coracoid process, and extends down the arm following the medial border
of the biceps for a short
distance below the insertion of the pectoralis major. The triangular
flap of skin and platysma
between the upper longitudinal and infraclavicular incision is
reflected outward, at which time
the external jugular vein is met and divided between forceps. To gain a
better exposure of the
lower trunk of the plexus, the later altendon of insertion of the
sternomastoid muscle may be
divided close to its attachment to the clavicle. The deep fascia now
being exposed is divided
along the course of the skin incision and retracted laterally with its
underlying cushion of fat.
During this procedure the posterior belly of the omohyoid muscle is
exposed and may be divided
to obtain a more satisfactory exposure of the plexus. The prevertebral
layer of the deep fascia is
now exposed and the several transverse cervical vessels lying in front
of it are ligated and
divided. The prevertebral fascia is divided longitudinally, and the
lateral border of the scalenus
anticus muscle identified and exposed as it lies under the
sternomastoid. The upper trunk of the
plexus, formed by the anterior divisions of the fifth and sixth
cervical nerves, will be found
emerging from the lateral borderof the scalenus anticus. These trunks
lie upon the scalenus
medius muscle, the fifth being found to emerge from behind the lateral
border of the
scalenusanticus, opposite the transverse process of the fifth cervical
vertebra, and if followed
downward, it will be found to unite with the sixth, forming the upper trunk of the plexus, which
in turn divides into three branches, a smaller and lateral branch, the
suprascapular nerve; an
anterior branch (anterior division)uniting with the anterior division
of the middle trunk to form
the outer cord of the plexus; and a posterior branch (posterior
division) uniting with the poste-rior divisions of the middle and lower
trunks to form the posterior cord. If the
988
lesion extends below the
upper trunk, involving its anterior or posterior division, it will be
necessary to divide the clavicle in the exposure. This division of the
clavicle should be done
subperiosteally, in its middle third, with a Gigli saw. It is advisable
to drill holes through the
clavicle before its division, to facilitate its later approximation
with wire.
When
lesions involve the plexus in its lower or subclavicular region, the
lower vertical
limb of the "step-shaped" incision is carried down the arm as far as
exposure seems necessary,
usually some distance below the insertion of the pectoralis major
muscle. The line of cleavage
between the pectoralis major and deltoid is found and these muscles are
separated and retracted;
while
FIG. 165.- Infraclavicular
exposure of
brachial plexus. Line of cleavage deepened between pectoralis major and
deltoid; forceps passed under pectoral tendon, preparatory to division.
A, Deltoid; B, cephalic vein C, biceps; D,
pectoralis major
the adjacent
fibers of these two muscles run parallel, the cephalic vein indicates
the line of
cleavage. In making this separation, the vein should be allowed to
remain on the deltoid side and
be carefully preserved, the line of cleavage being followed to the
clavicle. To obtain exposure of
the subclavicular portion of the plexus, the insertion of the
pectoralis major into the humerus and
of the pectoralis minor into the coracoid process may be divided, and
these muscles retracted
medially; after this retraction, the subpectoral fascia is divided,
exposing below the
neurovascular bundle. The lateral or medial end of the divided clavicle
may be retracted by strips
of heavy sterile bandage. The cords of the brachial plexus may now be
identified by following
upward their
989
terminal branches. The
identification of the median nerve, which is the most superficial, is
facilitated when followed upward, by its division into its respective
outer and inner heads, in the
fork of which will be found the axillary artery. If the outer head of
the median is followed
upward, it is found to join with the musculocutaneous nerve, forming
the outer cord of the
plexus. Following the inner head upward, it will be found to unite with
the ulnar nerve and the
internal cutanei, forming the inner cord of the plexus; in this manner
both outer and inner cords
are readily identified. In the axilla, the axillary artery is found
lying immediately posterior to the
median nerve. The loose connective tissue
FIG. 166.- Infraclavicular
exposure of
brachial plexus; pectoralis major divided and reflected; neurovascular
bundle
exposed and sheath held open by forceps; biceps retracted laterally to
facilitate exposure. A, Deltoid; B, pectoralis
major tendon, divided; C, coracobrachialis; D, biceps; E, median, outer
head; F. median, inner head; F, median
nerve; U, ulnar nerve; I, internal cutaneous nerve; J, pectoralis
major, reflected; K, neurovascular bundle; L, axillary
artery
uniting these structures
may be carefully separated, and posterior to the artery the
musculospiral
nerve is identified, which when followed upward is found to unite with
the circumflex, and by
this union to form the posterior cord. Probably the greatest difficulty
in isolating the components
of the neurovascular bundle below the clavicle is found in the bleeding
from the division of
numerous venous radicals. It is wise, therefore, early in dissection,
to carefully isolate the axillary
vein, beginning this dissection in the lower part of the incision. The
presence of scar tissue
greatly complicates the dissection of that portion of the plexus which
lies in direct contact with
the axillary artery and vein; if there is
990
evidence of an aneurysm,
it is well to carefully expose the artery proximal to the aneurysm
before
its dissection is attempted, so that control of hemorrhage maybe
assured in case of accident. In
isolating the axillary vessels in this region, caution should be used
toward identifying and
preserving the anterior thoracic nerves, the external of which in
arising from the outer cord of the
plexus passes over the artery, while the internal, arising from the
inner cord passes under the
artery; both branches usually pass over the axillary vein. If the
preoperative report shows the
pectoral muscles to be intact, the identification of the anterior
thoracic nerves may be facilitated
by electrical stimulation. These nerves
FIG. 167.- Infraclavicular
exposure of
brachial plexus. Median nerve retracted medially, exposing origin of
outer
head of the median and musculocutaneous nerve, behind which is seen the
musculospiral nerve passing over the
latissimus dorsi tendon, and the circumflex nerve accompanied by the
circumflex artery, passing through the
quadrilateral space in the posterior wall of the axilla. A, Deltoid; B,
coracobrachialis; C, musculospiral nerve; D,
latissimus dorsi tendon; E, coracoid process; F, pectoralis minor,
tendon divided; G, median, outer head; R, musculocutaneous nerve; I,
median nerve; J, circumflex nerve; K, circumflex artery; L, pectoralis
major, tendon
divided
enter the muscles on
their under surface. In exposing the lower trunk of the plexus, both
artery
and vein must be well isolated and retracted downward. A mastery of the
situation in difficult
brachial plexus dissections can be assured only after thorough
isolation of the adjacent vascular
channels, and the preliminary attention given to this aspect of the
procedure, though often time-consuming, is in the end a time-saving
procedure. Occasionally the artery, will be found so
constricted by scar tissue as to render it a nonpulsating cord, which
may closely resemble a nerve
in appearance. In such cases the preliminary identification and
exposure of the artery will avoid
much trouble. It has occasionally been possible to restore pulsation in
a compressed brachial
991
artery by the removal of
constricting scar tissue. If this procedure fails to restore
circulation, the
vessel is probably obstructed by a thrombus. If collateral circulation
is defective, arteriotomy may
be attempted and the thrombus removed with the aid of a dull ring
curette. After a free flow of
blood has been obtained from both directions, the vessel may be closed
with ordinary vascular
sutures. When brachial plexus lesions are associated with irritative
syndromes, the operator
should never neglect the removal of scar tissue from the artery, and
occasionally a decortication
is indicated, after the method of Leriche. The importance of vascular
lesions in this region, in the
production of both painful and ischemic syndromes, can not be
overestimated, and any effort
devoted to the reconstruction or liberation of vascular channels is
well worth while, even though
collateral circulation seems to be adequate.
At
this point it might be well to reiterate the necessity of physiologic
preservation of the
various plexus components and to emphasize the importance of
conservatism in resection.
Sutures of the plexus proper, because of distortion of normal nerve
pattern, have given very
unsatisfactory results; and unless the surgeon feels confident in his
ability to preserve, at least to
some degree, the original intraneural topography, far better results
will probably attend a
carefully executed external and internal neurolysis. The internal
neurolysis, however, should be
confined almost entirely to the resection of scar-invaded portions of
the nerve sheath. Suture of
the terminal divisions of the plexus is a far more satisfactory
procedure in that it is possible to
preserve in a large measure the original nerve pattern by the
prevention of torsion during suture.d
THE CIRCUMFLEX NERVE
GENERAL ANATOMY
The
circumflex nerve receives its fibers from the ventral division of the
fifth and sixth
cervical nerves through the posterior cord of the brachial plexus, in
which it occupies a position
lateral to the fibers forming the musculospiral, though within the same
sheath. Near the outer
border of the subscapularis the circumflex leaves the musculospiral to
pass with the posterior
circumflex vessels through a quadrilateral space in the posterior wall
of the axilla, which is
formed by the teres minor and subscapularis above, the teres major
below, the long head of the
triceps medially, and the humerus laterally. The nerve then winds
around the surgical neck of the
humerus posteriorly, and lying upon the under surface of the deltoid
sends fibers to this muscle.
In the region of the quadrilateral space the circumflex nerve divides
in to an upper and a lower
branch. The upper branch winds around the surgical neck of the humerus
and supplies the bulk of
the deltoid muscle; it also distributes cutaneous branches which pierce
the muscle and supply the
integument over the deltoid region. The lower branch gives off
filaments to the teres minor and
to the posterior fibers of the deltoid, after which it pierces the
integument, which it supplies with
sensation over the lower posterior deltoid region.
d The
technique of physiologic approximation in
suture of the terminal branches of the brachial plexus is
considered in detail under the surgery of these respective individual
nerves.
992
SURGERY
AXILLARY EXPOSURE
Exposure
of the circumflex nerve is obtained, as in low lesions of the brachial
plexus,
with the arm in outward rotation and marked abduction. The incision is
made over the course of
the neurovascular bundle from the middle of the clavicle to a few
centimeters below the tendon
of the pectoralis major. The deltoid is separated from the pectoralis
major and the cleft between
these muscles deepened to expose the deep pectoral fascia. (See figs.
165,166, 167.) The
pectoralis major is divided near its insertion into the humerus and
reflected. The deep pectoral
fascia is now divided to expose the neurovascular bundle. The median
nerve and the axillary
artery are identified and retracted medially, exposing the
musculospiral nerve passing over the
latissimus dorsi tendon. The musculospiral nerve is now followed upward
toa, point near the
insertion of the pectoralis minor, where the circumflex will be found
joining its lateral side to
form the posterior cord of the brachial plexus. When thus identified
the circumflex nerve may be
followed around the medial side of the neck of the humerus to where it
leaves the axilla by
passing through the quadrilateral space to the dorsum of the arm.
DORSAL OR LATERAL EXPOSURE
Occasionally
the circumflex nerve is injured after it has left the axilla in its
passage
around the surgical neck of the humerus. To approach lesions in this
region a dorsal or lateral
exposure is needed. The patient lies on his side with the arm acutely
flexed across the chest,
giving access to the posterior deltoid region. A longitudinal incision
is now made approximating
closely the dorsal border of the deltoid. This muscle is elevated and
retracted forward. Retraction
may be facilitated by elevation of the arm, relaxing the deltoid.
Occasionally it will be found
advisable to divide some of the posterior deltoid fibers. The
circumflex nerve will be found
hugging the neck of the humerus, as it emerges from the quadrilateral
space, accompanied by the
posterior circumflex artery and its venae comites.
Isolated
lesions of the circumflex nerve are comparatively rare, though deltoid
paralysis is
frequently associated with brachial plexus lesions, particularly those
involving the upper trunk.
Fortunately, the muscles of the shoulder girdle are supplied by
branches given off from the
brachial plexus at various points, so that a total paralysis of the
shoulder is seldom encountered
except in complete brachial plexus lesions. Individual nerves supplying
the muscles of the
shoulder and shoulder girdle run a relatively short course before
breaking up into terminal
branches to supply their respective muscles, so that their repair is as
a rule exceedingly difficult;
in fact their short course usually eliminates the possibility of
effecting end-to-end approximation
where a defect is present. Practically the only recourse the surgeon
has when confronted with a
serious defect in a nerve of short course is to resort to nerve
grafting or viable transplants. This is
particularly true in regard to isolated lesions of the circumflex
nerve.
993
In
irreparable lesions of the circumflex nerve and in those instances in
which partial
brachial plexus lesions are associated with deltoid paralysis and the
loss of humeral abduction,
arthrodesis of the shoulder joint gives perhaps more satisfactory
results than any form of tendon
transplantation if the scapular muscles have been preserved. The
usefulness of this operation,
however, depends entirely upon the preservation of scapular rotation. e
THE
MUSCULOCUTANEOUS NERVE
GENERAL ANATOMY
The
musculocutaneous nerve receives its fibers from the outer cord of the
brachial plexus,
in common with the outer head of the median below the clavicle. In the
region of the neck of the
humerus it leaves the neurovascular bundle and passes laterally between
the two heads of the
coracobrachialis to the under surface of the biceps, where it divides
into a number of branches
supplying this muscle and the brachialis anticus. Its sensory portion
continues down the arm, and,
emerging from between the biceps and the brachialis anticus, penetrates
the deep fascia and
pursues a subcutaneous course down the lateral side of the forearm,
supplying the integument. As
the musculocutaneous nerve enters its canal between the heads of the
coracobrachialis, it gives
off a branch to this muscle, which, though running directly with the
musculocutaneous nerve and
usually incorporated within its sheath, derives its fibers from the
seventh cervical and is, to all
intents and purposes, a special nerve as the musculocutaneous is
derived solely from the fifth and
sixth cervical.
Anatomic
irregularities of the musculocutaneous nerve are too varied to be
considered in
detail; they consist principally of various communications with the
median nerve. Occasionally a
portion of the median nerve may follow the course of the
musculocutaneous, and after this nerve
gives off branches to the biceps and brachialis anticus the divergent
fibers will again join the
medial trunk; in other instances the branches to the biceps and
brachialis anticus may spring
directly from the median trunk. It is not uncommon to find various
anomalous communications
between the musculocutaneous and median nerves in various degrees. A
consideration of these
abnormalities will assist in explaining certain types of combined
lesions which are at times
inclined to be rather perplexing. The possibility of anatomic
irregularities should always be
considered when the clinical findings point to a combined partial
musculo- cutaneous and
median lesion.
SURGERY
Lesions
of the musculocutaneous nerve may occur in any part of its course; in
the upper
portion of the arm, or in the axilla, it may be associated with
concomitant lesions of the
neurovascular bundle, though isolated lesions are
e The writer has recently observed a case of
infantile paralysis in which the deltoid was completely paralyzed.
though fairly effective abduction of the humerus by the short head of
the biceps was possible. The possibility was
immediately suggested of changing the point of origin of the short head
of this muscle to a more lateral position by
inserting it into the acromlon process under the deltoid; this might
also be reinforced by transplanting the long head
of the triceps Into this same position. Experimental work on the
cadaver demonstrates the possibility of this
procedure from an anatomic standpoint. Traction on these transposed
muscles in a line corresponding to what would be their action after
transposition results in forcible abduction of the arm. He has not had
occasion to attempt this
transplant clinically, but believes that it offers a possible means of
humeral abduction in deltoid paralysis when
bicipital and tricipital function is preserved.
994
by no means rare. If the
nerve is injured in the lower third of the arm the motor fibers usually
escape injury, its sensory portion alone being involved.
EXPOSURE
The
exposure of the musculocutaneous nerve in the upper portion of the arm
may be
made as in lower plexus lesions. A long incision follows the medial
border of the
coracobrachialis, beginning a few centimeters below the clavicle and
extending downward to the
middle of the arm. The superficial fascia is divided, exposing the
coracobraehialis. The line of
cleavage between the pectoralis major and deltoid is deepened and the
deep pectoral fascia
exposed, care being taken to preserve the cephalic vein, which runs in
the cleft between these
muscles. It is usually necessary to divide the tendon of insertion of
the pectoralis major to obtain
access to the origin of the nerve. (See figs.165,166,167.) The
pectoralis major is retracted
medially and the pectoral fascia covering the neurovascular bundle in
the axilla divided,
exposing the median nerve, which may be identified bv electrical
stimulation, though this is
rarely necessary. If the nerve be followed upward, it will be found to
divide into an inner and
outer head, between which lies the axillary artery. Springing from the
lateral side of the outer
head will he found the musculocutaneous nerve, which abruptly leaves
the neurovascular bundle
afnd enters its canal between the two heads of the coracobrachialis.
When
the lesion is below the branch to the coracobrachialis, the
musculocutaneous nerve
may be exposed without invading the axilla. A longitudinal incision is
made over the upper
portion of the biceps, and the line of cleavage between its two heads
found and deepened. In the
recess, the musculocutaneous nerve will be found lying upon the
coracobrachlialis. The nerve
may now be followed along the under surface of the biceps by extending
the line of cleavage
between the long and short head downward through the substance of the
muscle. In this way the
motor branches may be adequately exposed. The motor branches spring
from the lateral portion
of the nerve trunk; the sensory from its medial side. A recognition of
this fact will serve to
facilitate physiologic approximation.
DEFECTS
Defects
in the musculocutaneous nerve may be overcome to some extent by the
relaxation
obtained in flexing and adducting the arm over the chest. Defects not
correctable in this manner,
nor by stretching, will require grafting or a viable transplant. In
closing the incision, if the tendon
of the pectoralis major has been divided it should be carefully sutured
with 20-day chromicized
gut, and the arm maintained in flexion and adduction by strapping the
hand to the opposite
shoulder.
EXPOSURE OF TIHE SENSORY PORTION
Lesions
involving the musculocutaneous nerve in the lower third of the arm are
not
accompanied by motor disability in this region the nerve is entirely
sensory. Occasionally,
however, certain irritative lesions necessitate its exposure, when it
may be sectioned or subjected
to alcoholic injection. The
995
sensory portion of the
nerve is occasionally utilized as material for autogenous grafts. Its
exposure is made through an incision along, the lateral surface of the
arm corresponding to the
medial border of the brachioradialis. The nerve will be found emerging
from beneath the lateral
border of the biceps, after which it pierces the deep fascia to become
subcutaneous in the
forearm. The biceps may be retracted meldially, and the nerve followed
upward beneath this
muscle to the junction of the middle and lower third of the humerus,
where it may be sectioned
without injury to motor branches.
IRREPARABLE DEFECTS
Paralysis
of the muscles supplied by the musculocutaneous nerve is not
particularly
disabling, as their function consists almost entirely in forearm
flexion, which may he very
satisfactorily accomplished in biceps paralysis by the brachioradialis,
which muscle is supplied
by the musculospiral nerve, though flexion by this muscle is usuallv
associated with some degree
of supination, which is corrected by action of the pronator radii
teres. also capable of some
forearm flexion. If an irreparable musculocutaneous lesion is combined
with a permanent
paralysis of the brachioradialis, pronator teres flexion of the elbow
alone will be of little practical
assistance, as its flexor power is weak and always associated with
marked pronation. Under such
conditions, apparently the only recourse is in arthrodesis of the elbow
joint, immobilizing it in a
position of flexion compatible with the needs of the individual.
MUSCULOSPIRAL NERVE
GENERAL ANATOMY
The
musculospiral nerve is a continuation of the posterior cord of the
brachial plexus,
which in turn is formed by the posterior trunks of the anterior primary
divisions of the fifth, sixth,
seventh, and eighth cervical nerves. In the early part of its course it
occupies a position dorsal to
the axillary artery in the neurovascular bundle and pursues a somewhat
spiral course posteriorly
around the humeral shaft, and gains the lateral surface of the arm by
penetrating the external
intermuscular septum. In the lower part of the arm. it passes from a
lateral to a ventral position at
the elbow and there divides into two terminal branchles. the radial and
posterior interosseous
nerves.
BRANCHES
In
the axilla and on the inner side of the arm, which constitutes its medial
portion. the
musculospiral nerve gives off three branches: The internal cutaneous: a
muscular branch to the
long head of the triceps; and a muscular branch to the medial head of
the triceps, sometimes
called the ulnar collateral. In its posterior or intratricipital portion it gives off two external
cutaneous branches and muscular branches to the lateral and medial
heands of the triceps. On the
external surface of the arm, lateral portion, branches are
given off to the brachioradialis, the
extensor carpi radialis longior, and occasionally a small branch to,
the brachchialis anticus.
996
Terminal
branches.-The radial nerve passes down the radial side of the
forearm, under
cover of the brachioradialis muscle, to the dorsum of the hand; it is
purely sensory and supplies
sensation to the dorsum of the lower third of the forearm, hand, and
fingers.
The posterior interosseous nerve carries chieflv motor fibers; passing
under the
brachioradialis muscle it pierces the supinator brevis, and in its
passage through this muscle
winds around the shaft of the radius to appear on the dorsum of the
forearm. Before entering the
supinator canal it gives off branches to the extensor carpi radialis
brevior and the supinator
brevis. Shortly after it emerges from the lower border of the supinator
it fans out into a number of
branches which supply the extensor communis digitorum, extensor
carpi ulnaris, and extensor
minimi digiti. A little lower in the forearm other branches are given
off to the extensor ossis
metacarpi pollicis, extensor longus and brevis pollicis. and extensor
indicis.
SURGERY
From
a standpoint of surgical accessibility, we shall consider the
musculospiral nerve as
having medial, dorsal, and lateroventral portions, with two terminal
branches, the posterior
interosseous and radial nerves.
MEDIAL PORTION
The
medial portion of the musculospiral constitutes that part of the nerve
trunk which lies
medial to the humerus, extending from its origin in the axilla to where
it crosses the long head of
the triceps. In the upper part of its medial course the musculospiral
nerve lies posterior to the
axillary artery; in the lower part of the axilla it leaves the
neurovascular bundle and, passing over
the tendons of the teres major and latissimus dorsi, it begins its
dorsal or intratricipital course by
passing anterior to the long head of the triceps. From the medial
portion of the musculospiral
three branches are given off from the medial side of the nerve trunk-an
internal cutaneous branch
and two motor branches, one of which supplies the long head of the
triceps, the other, known as
the ulnar collateral, supplies the medial head of the triceps. These
branches may be followed
some distance up the nerve trunk, where they will be found to unite
with two distinct bundles.
The internal cutaneous branch unites with the bundle which in the
dorsal portion of the nerve's
course forms the external cutaneous. In other words, the sensory fibers
contained in the internal
and external cutaneous branches spring from a common bundle and
separate from the parent
trunk either combined or as separate branches. The identification of
one sensory branch, if
followed intraneurally, will serve to identify the other by their
intraneural union. They may be
identified distally by a careful dissection which will demonstrate
their cutaneous termination.
The two motor branches may be given off from the musculospiral trunk
individually or, as
occasionally happens, all the motor branches to the triceps will be
found leaving the nerve trunk
as a single large branch, later subdividing and forming the individual
branches to its respective
heads. More often the tricipital branches are loosely incorporated
within the
997
musculospiral sheath,
though they are distinctly individual and may possess a well-developed
sheath of their own. The bundle containing the tricipital branches
occupies a very definite
position upon the medial side of the nerve, ventral to the cutaneous
sensory bundle. The larger or
lateral bundle constitutes that portion of the nerve which gives off
branches to the supinator and
extensors, ultimately terminating in the radial and posterior
interosseous nerves. Lesions of the musculospiral nerve in its medial
portion are often
FIG. 168.- Exposure of
medial portion of
musculospiral nerve in the axilla and upper portion of the arm. Tendon
of
pectoralis major divided. Median and ulnar nerves with brachial artery,
retracted medially, exposing musculospiral
nerve and superior profunda artery, as they cross the tendon of the
latissimus dorsi and long head of the triceps
entering their posterior humeral course. The branches of the medial
portion of the musculospiral are shown springing
from the medial aspect of the musculospiral trunk. A, Median nerve,
outer and inner head; B, musculospiral nerve;
C, axillary artery; D, pectoralis major, reflected; E, musculospiral
medial branches; F, superior profunda artery; G,
brachial artery; H, latissimus dorsi tendon; I, coracobrachialis; J,
deltoid; K, Pectoralis minor tendon
combined lesions,
corresponding to terminal plexus types, and frequently are associated
with
vascular injury.
The
method of exposure of the musculospiral nerve in its upper medial
portion within the
axilla is the same as that used in infraclavicular plexus lesions. Its
lower medial portion is
exposed through a straight incision, extending from the base of the
axilla to the middle of the
humerus, in a line corresponding to the medial edge of the
coracobrachialis. The deep fascia is
divided, exposing the neurovascular bundle; by ligating a few branches
of the brachial artery and
their accompanying veins, the contents of the neurovascular
998
bundle may be retracted
medially, and the musculospiral nerve located as it crosses the
latissimus
dorsi tendon, accompanied by the superior profunda artery; or it may be
located before it leaves
the neurovascular bundle, where it lies behind the brachial artery. Its
cutaneous and motor
branches should now be identified as they leave the nerve trunk from
its medial surface. The
motor branches are identified readily by following them to a muscle
termination, while the
internal cutaneous branch will be found to penetrate the deep
FIG.
169.-Exposure of
median portion and internal part of posterior portion of musculespiral
trunk through medial incision. Contents of neurovascular bundle
retracted medially; superior
profunda artery ligated; complete exposure of tricipital branches;
intraneural dissection, showing
their origin from medial side of the musculospiral trunk. A, Deltoid;
B, biceps; C,
coracobrachialis; D, superior profunda artery, ligated; E, pectoralis
minor tendon: F, pectoralis
major, reflected; G, musculospiral nerve; H, median nerve; I, internal
cutaneous branch: J,
latissimnus dorsi tendon; K, tricipital branches
fascia to assume a
cutaneous position. Retraction of the long head of the triceps will
permit very
satisfactory exposure of the nerve on the medial side of its
intratricipital course, where it will be
found passing lateral to the medial head of the triceps as it enters
the musculospiral groove on the
posterior surface of the humerus. Division of a few of the internal
fibers of the medial head ofthe
triceps will permit adequate exposure of the nerve through most of its
posterior course. This
medial incision is also frequently required to gain access to the nerve
in its dorsal position.
999
DORSAL PORTION
The
dorsal or intratricipital portion of the musculospiral is that part of
the nerve which
lies posterior to the humerus and is covered by the triceps. The nerve
enters the posterior surface
of the arm by passing anterior to the long head of the triceps shortly
after it has left the
neurovascular bundle. In its dorsal course it first lies on the ventral
surface of the long head of
the triceps; then occupying a position in direct contact with the
humerus it passes through the
musculospiral groove, just above the origin of the medial head of the
triceps and below the origin
of the lateral head of the triceps, which latter covers the nerve.
Having pursued a somewhat spiral
course around the humeral shaft, the nerve emerges from its dorsal
position by penetrating the
external intermuscular septum to appear on the lateral aspect of the
arm. In its dorsal course, the
nerve is accompanied by the superior profunda artery and its
accompanying vein, which lie
lateral to the nerve. The superior profunda artery, upon reaching the
external intermuscular
septum, divides into two branches, the smaller of which penetrates the
intermuscular septum and
accompanies the musculospiral nerve; the larger branch follows along
the posterior surface of the
intermuscular septum to the elbow. In its dorsal portion the
musculospiral nerve gives off
branches to the lateral and medial heads of the triceps. These branches
almost invariably lie on
the medial side of the nerve, and may be followed up the nerve trunk as
individual branches or as
a single bundle into the axilla. The external cutaneous nerve, though
given off with the internal
cutaneous from the medial side of the musculospiral nerve, crosses the
parent trunk and follows
its lateral surface with the profunda artery where it divides into a
superior and an inferior
cutaneous branch. These cutaneous branches do not penetrate the
external intermuscular septum,
though the inferior branch passes over it and becomes cutaneous near
the elbow.
The
nerve in this region, occupying a position in direct contact with the
humerus, is
frequently injured in fractures of the middle third. It may be
completely crushed by the trauma
producing the fracture, though probably it is more often traumatized
and stretched by the bone
fragments at the time of injury or during efforts at fracture
reduction. Occasionally it is found
compressed or completely buried in the callus of an old fracture.
Exposure
of the musculospiral nerve in its dorsal position may be accomplished
by
several methods:
A. Dorsal longitudinal incision.-An incision beginning about 7
centimeters below the
acromial process is carried down the middle of the posterior surface of
the arm to the junction of
its lower and middle thirds, in line with the olecranon. The deep
fascia is incised; and the
cleavage between the long and lateral heads of the triceps found and
deepened until the
aponeurosis of their ventral surface is encountered. This aponeurosis
is then carefully divided to
prevent injury to the musculospiral nerve and its branches, which lie
directly on its ventral
surface. In separating the long and lateral headsof the triceps upward,
the posterior fibers of the
deltoid are retracted laterally, some of which may require division.
Retraction of the tricipital
heads will give a satisfactory though rather limited exposure of the
musculospiral groove
1000
and its contents. When
extensive scar tissue Is present, the dorsal incision should be
supplemented by a lateral incision, exposing the nerve as it emerges on
the lateral surface of the
arm, after penetrating the external intermuscular septum. The nerve is
identified at this point and
the lateral head of the triceps separated from its attachment to the
septum and retracted dorsally
exposing the lateral portion of the musculospiral groove. Occasionally
it will be found necessary to divide the lateral head of the triceps
and in
such instances the division should he made as high as possible to avoid
injury to its nerve supply. A piece of tape passed under the lateral
head of the triceps between these two
incisions will often permit sufficient retraction of the muscle from
the humerus to expose the
nerve throughout its course in the musculospiral groove. In attempting
retraction or division of
the lateral head of the triceps through the combined dorsol lateral
incisions, the greatest care
should be used to prevent injury to the tricipital branches, which at
first should be identified and isolated in
the upper portion of their course. The operator frequently experiences
difficulty in this dissection, due to injury of the superior profunda
artery and veins. It is expedient, therefore, early in the exposure,
to secure primary ligation of the artery in the upper part
of the wound and ligation of the veins dorsal to the external
intermuscular septum.
B. Exposure of the dorsal portion of the
musculospiral by a combined medial lateral
incision.-The medial portion of the musculospiral groove may be
readily approached through the
low incision described for exposure of the
FIG. 170.- Showing
course of musculospiral nerve, and
relation of
branches to triceps, as it passes behind humerus in
musculospiral groove. Preservation of branches in transposing nerve to
anterior position. (Ney, Annals of
Surgery,
1921)
musculospiral in the
lower part of its medial portion, by retracting medially the
neurovascular
bundle groove may be readily approached through the low incision
described for exposure of the
musculospiral in the lower part of the medial portion, by retracting
medially the neurovascular
bundle, and dorsally the long head of the triceps. This approach will
also facilitate control of the
profunda artery and the identification and isolation of the tricipital
branches. This medial
exposure is supplemented with the lateral incision, through which the
musculospiral nerve is
identified as it penetrates the external intermuscular septum, and the
attachment of the lateral
tricipital fibers freed from this structure. In this procedure the long
and lateral heads of the triceps
are retracted from the humerus, exposing the nerve throughout its
intratricipital course. The
advantage of this method is obvious; it gives a complete exposure of
the nerve and all its tricipital
1001
branches it permits
of satisfactory heinostasis. in that the profunda artery may be secured
above and the veins below; and in the presence of extensive continuity
defects, it permits
transposition of the nerve to an antebrachial position by allowing
mobilization of the nerve trunk,
without endangering its branches and without additional incisions.
The
proximity of the musculospiral nerve to the humerus in its, dorsal
course frequently
calls for the preparation of a new nerve bed. When this is
necessitated, because of extensive
callus or sear tissue, the nerve may be separated from direct contact
with the bone by changing its
course from the musculospiral groove to a lower position where it is
made to pass behind the
medial head of the triceps. This procedure requires mobilization of the
nerve through its lateral
portion, and low separation of the lateral head of the triceps from the
external intermuscular
septum, permitting the nerve to follow a lower dorsal course between
the medial and lateral
heads of the triceps. When extensive bone callus or scar tissue
involves the posterior surface of
the humerus and the tricipital heads, recourse should be had to an
antebrachial transposition, in
which the nerve is directed anterior to the humerus, between the biceps
and the brachialis anticus.
VENTROLATERAL PORTION
The
ventrolateral portion of the mnusculospiral nerve constitutes that
portion of the nerve
which lies lateral and ventral to the humerus on the external aspect of
the arm, beginning at the
external intermuscular septum and terminating in front of the external
humeral condyle, where it
bifurcates into its two terminal branches. In its ventrolateral course,
in passing down the lower
third of the arm, the nerve is deeply placed between the
brachioradialis and brachialis anticus. In
the region of the external humeral condyle, the nerve is covered by the
braclioradialis and rests
upon the brachialis anticus. This portion of the nerve gives off a
branch to the brachioradialis
shortly after entering the lateral surface of the arm. A little lower,
a branch is given off to the
extensor carpi radialis longior. These motor branches emerge from the
lateral side of the
musculospiral trunk, the branch to the brachioradialis being the most
ventral of the lateral group
of motor fibers. Immediately behind this branch lies the bundle
containing the fibers to the carpal
extensors. The branch to the extensor carpi radialis brevior is
occasionally given off with the
branch to the long carpal extensor, though more frequently it leaves
the nerve trunk from its
terminal posterior interosseous division. It has, however, a long
intraneural course, and if
followed up the nerve will be found to spring from a bundle common to
both radial extensors. Injuries to the musculospiral in this region are
probably more often encountered in military
surgery than injuries to any other nerve. It is a common complication
of fractures of the lower
third of the humerus, and in civil life the frequency of its occurrence
is approximated only by
lesions of the ulnar in the region of the internal epicondyle. In
simple fractures the trauma to the
nerve consists usually in stretching, or bruising against bone
fragments; in the absence of an open
wound it is rarely divided. Paralysis of the musculospiral
1002
nerve bv pressure
has frequently been observed following the use of a tourniquet, and
surgeons who insist, upon its use should remember this possibility and
endeavor to protect the
musculospiral region by properly placed pads.
Exposure
of the lateroventral portion of the musculospiral is made through
a longitudinal
incision, extending from the insertion of the deltoid to a point midway
between the biceps tendon and the external condyle of the humerus. In
the lower part of the incision the cephalic vein is
divided between forceps. In the upper part of the incision, the lateral
cutaneous branches may
be met, and,
FIG. 171.- Landmarks for
exposure of
musculospiral nerve in its latero-ventral aspect, showing external
intermuscular septum, from the ventral side of which arises fibers of
the brachioradialis, and from its dorsal surface,
fibers of the lateral head of triceps. Musculospiral nerve is exposed
by deepening the cleft between brachioradialis
and biceps which lies ventral to the latter muscle. A. Biceps; B,
brachioradialis; C, triceps, lateral head; D, external
intermuscular septum
FIG. 172 .– Musculospiral
nerve,
latero-ventral aspect, showing emergence on lateral surface of arm,
after
penetraging external intermuscular septum. A, Biceps; B. Brachialis
anticus; C, musculospiral nerve; D, superior
profunda artery E, triceps, lateral head; F. External intermuscular
septum; G, brachioradialis
if necessary, sacrificed
with impunity. The line of cleavage between the brachioradialis
laterally
and the biceps and brachialis anticus medially is identified and these
muscles retracted. In the
cleft, deeply placed, the musculospiral nerve is found accompanied by a
small terminal branch of
the superior profunda artery. Occasionally, the inferior external
cutaneous branch, which
1003
is of fairly large size,
will be found passing along the external intermuscular septum and
should
not be mistaken for the inusculospiral trunk. It will often serve as a
guide, if followed upward, in
locating the musculospiral. f
The
musculospiral trunk should be isolated above the lesion to facilitate
branch
identification and preservation, even though it be necessary to invade
its dorsal or intratricipital
portion. In following the nerve downward, between
FIG. 173.- Musculospiral
nerve,
postero-lateral aspect; lateral head of triceps divided close to
attachment to external
intermuscular septum, exposing nerve in lateral aspect of its dorsal
course in musculospiral groove. A,
Musculospiral nerve; B, triceps, lateral head, divided; C, biceps; D,
brachialis anticus; E, external intermuscular
septum; F, brachioradialis.
FIG 174.- Musculospiral
nerve at elbow, showing
terminal posterior
interosseous and radial divisions. Brachioradialis divided. Intraneural
dissection of branches shows them springing from lateral side of
musculospiral
trunk. Radial nerve is given off from ventro-medial aspect of
musculospiral trunk; posterior interosseous nerve arises
from dorso-lateral portion of trunk. A, Musculospiral nerve; B,
posterior interosseous nerve; C, radial nerve; D,
brachioradialis, divided; E, brachialis anticus; F, extensor carpi
radialis longior; G, branch to extensor carpi radialis
brevior
the brachioradialis and
the brachialis anticus, extreme care should be used in preserving motor
branches. In the upper part of this region, if the circumference of the
musculospiral nerve be
divided into a lateral, posterior, and medial sector, the lateral
sector will be found to contain
motor fibers to the brachioradialis and carpal extensors, the posterior
sector will contain those I
f The
writer has on one occasion reoperated a
case of musculospiral paralysis which failed to regenerate, and found
the proximal end of the musculospiral anastomosed to the distal segment
of this branch; in the original operation, the
surgeon had apparently mistaken the cutaneous branch for the
musculospiral trunk.
1004
motor fibers which
eventually forii the posterior interosseous nerve, and the medial
sector will
contain sensory fibers ultimately forming the radial terminal division.
In
the region of the external condyle, the musculospiral nerve lies upon
the brachialis
anticus and under cover of the brachioradialis. Strong lateral
retraction of the latter muscle will
expose the nerve where its two terminal branches may be identified-the
posterior interosseous,
arising from its lateral and posterior sector; and the radial, arising
from its medial sector.
INTEROSSEOUS NERVES
The
posterior interosseous nerve, containing mostly motor fibers,
innervates the
supinator, extensor carpi ulnaris, and extensors to the fingers and
thumb, and it constitutes the
terminal motor portion of the musculospiral trunk. After its separation
from the radial nerve on
the undersurface of the brachioradialis, it passes under the long and
short carpal extensors and
swings around the shaft of the radius to the dorsum of the forearm, by
passing through a canal in the substance of the supinator brevis
muscle, in a line almost at right angles to the
direction of the supinator fibers. After emerging from the lower border
of the supinator on the
dorsal surface of the forearm, the posterior interosseous nerve fans
out into a leash of branches
supplying the extensors of the fingers and thumb.
Lesions
of the posterior interosseous nerve below the upper third of the
forearm are rarely
amenable to suture, due to the breaking up of the nerve into a series
of small branches. Suture
may be effected, as a rule, only when the nerve is found injured in the
substance of the supinator
or proximal to that muscle. Occasionally, however, it will be found
possible to complete a satisfactory neurolysis in the region where the
nerve breaks up below the supinator. When it is found
impossible to restore the nerve supply to the digital extensors, it is
advisable to complete the
operation by tendon transplantation.
Exposure of
the posterior interosseous nerve.- A longitudinal incision is made
down the
posterior surface of the forearm in the midline, beginning at a point
two centimeters medial to the
external condyle and ending in the middle third of the forearm. The
deep fascia is divided and the
line of cleavage between the extensor carpi radialis brevior and the
extensor communis digitorum identified. These muscles are separated up
to their common origin at the external condyle and
retracted, exposing the fascia covering the supinator brevis muscle
below. The course of the
posterior interosseous nerve through the supinator is at almost right
angles to its fibers, and its
position may often be identified by palpation. Failing in this,
separation of the muscle fibers in their line of cleavage
will usually serve to locate the nerve, which is greatly flattened as
it passes
around the shaft of the radius. Exposure of the lower border of the
supinator will also aid in its
identification, as it emerges from this muscle.
The
posterior interosseous nerve may be completely exposed by dividing the
superficial
fibers of the supinator covering the nerve; by flexing the forearm and
retracting the radial carpal
extensors and the brachioradialis, it may be followed to its junction
with the radial. Extreme
care, however.
1005
should be used in
avoiding the branches supplying the supinator, which are usually given
off just
before the nerve enters this muscle or during its passage through the
muscle. Lesions within the supinator region of the posterior
interosseous as a rule mav be satisfactorily exposed through the
dorsal forearm incision; but when the lesion is located in its
presupinator portion, it is best exposed by separating
the long radial extensor from the brachioradialis
FIG. 175.- A, Supinator
brevis exposed by
separating extensor carpi radialis brevior and extensor longus
digitorum.
B, Intrasupinator portion of posterior interosseous nerve exposed by
dividing superficial fibers of supinator brevis.
Branches to supinator shown leaving the nerve in the substance of the
muscle. At lower border of supinator,
posterior interosseous fans out into a leash of branches, below which
repair is dlifficult. A. Extensor carpi radialis
brevior; B. supinator brevis; C, extensor longus dligitorurn; D,
posterior interosseous nerve: E. branches to
supinator; F, posterior interosseous, below supinator
through a slightly more
anterior incision, corresponding to a continuation of the lateral
musculospiral incision to the dorsum of the forearm. In exposing that
portion of the nerve lying
between its origin and the supinator (presupinator portion), great care
must be utilized to prevent
injuring the branch to the short carpal extensor, which is given off
from the anterior surface of
the nerve. It is usually of sufficient size, to permit of separate
suture. and efforts, should always
be made toward its conservation or repair.
1006
RADIAL NERVE
The
radial nerve constitutes the terininal sensory division of the
musculospiral trunk; it
first lies under the brachioradialis and upon the brachialis anticus,
medial to the posterior
interosseous. It progresses down the ventral and radial surface of the
forearm under cover of the
brachioradialis muscle. At the junction of the upper and middle third
of the forearm it is joined
by the radial artery, which lies on its medial side and accompanies it
through the middle third of
the forearm. At the beginning of the lower third it leaves the artery
and passes under the tendon
of the brachioradialis to enter the posterior surface of the forearm,
where it supplies sensation to
the dorsum of the wrist, hand, and fingers.
SURGERY
The
radial nerve, being entirely sensory, is seldom exposed for repair. It
is, however,
occasionally used as a graft for filling continuity defects in other
nerves, because of its fairly
large size and the minimal degree of disability resulting from its
sacrifice; when used for grafts,
its uppermost portion is usually selected.
Exposure
of the radial nerve may be accomplished through an incision
beginning just
above the bend of the elbow, midway between the external humeral
condyle and the biceps
tendon, and carried longitudinally down the radial surface of the
forearm as far as necessary,
paralleling the medial border of the brachioradialis. The deep fascia
is divided an(l the medial
edge of the brachioradialis exposed and retracted. The radial nerve may
be identified passing
along the under surface of this muscle, and may be followed up to a
point where it joins the
posterior interosseous to form the musculospiral trunk.
CONTINUITY DEFECTS
The
correction of defects in the continuity of the musculospiral nerve
differs in no way
from those methods used in overcoming defects in other nerves except in
transposition, when the
musculospiral nerve is changed from its spiral course around the
posterior aspect of the humerus
to the more direct ventral course anterior to the humerus, where it is
made to pass between the
biceps and the brachialis anticus, following a course similar to that
taken by the musculocutaneous nerve.
TECHNIQUE OF MUSCULOSPIRAL TRANSPOSITION
The
musculospiral nerve is exposed in its medial portion (see technique of
low exposure
of the medial portion of the musculospiral nerve, p. 997); the branches
to the triceps are
identified by retraction of the triceps and mobilized from the
musculospiral trunk.
The
musculospiral is exposed and freely mobilized from the external
intermuscular
septum to its terminal branches, using care to prevent injury to
branches in this region. The
lateral head of the triceps is separated from its attachment to the
external intermuscular septum
and carefully separated from the humerus along the course of the
musculospiral groove. A piece
of tape is passed through the tunnel between the lateral and medial
incisions, and the
1007
triceps by this means
retracted from the bone, completely exposing the nerve. It is important
that
the ends of the nerve be marked with identification sutures before the
nerve trunk has been
rotated during mobilization.
A
second tunnel is made connecting the lateroventral incision with the
medial, by
identifying the medial and lateral borders of the biceps and by blunt
dissection, separating this
muscle from the underlying brachialis anticus, following the line of
cleavage between these
muscles and using care to prevent injury to the musculocutaneous nerve.
The
musculospiral nerve is now drawn from its intratricipital course and
made to pass in
as direct a line as possible from the neurovascular bundle below the
axilla to its position medial
to the external humeral con(ldle below the biceps. After transposition,
the surgeon may avail
himself of flexion-relaxation to assist in overcoming any part of a
defect not corrected by the
transposition. It is particularly important to prevent torsion of the
nerve trunk during suture, and
the early placing of accurate identification sutures is essential as a
guide for restoring physiologic
alignment.
PHYSIOL.OGIC APPROXIMATION OF THE
MUSCULOSPIRAL AND ITS TERMINAL DIVISIONS.
The musculospiral nerve, by virtue of its motor
branches, lends
itself to physiologic
approximation more readily than any other nerve. While the prevention
of torsion is perhaps best
accomplished through effectively placed identification sutures, there
are certain instances,
particularly in secondary sutures, where this means of identification
can not be relied upon.
In
effecting suture of the medial portion of the musculospiral nerve,
identification of
tricipital branches will immediately demonstrate the medial side of the
nerve. In its posterior
position, the tricipital branches likewise indicate the medial side of
the nerve, though the lower
branches to the triceps occupy a more dorsal position. In the region of
the external intermuscular
septum, the nerve occupies a rather fixed position, which is not
readily disturbed by trauma: in
this position, the motor fibers lie in the lateral portion of the
trunk, the sensory fibers to the
medial side. The nerve in its course around the humerus, first contains
its motor fibers in its
medial side. Later, in the musculospiral groove, they become posterior,
the sensory fibers being
in contact with the humerus. In the region of the external
intermuscular septum the nerve
presents a different arrangement, due to a slight natural torsion in
its spiral course. In its
lateroventral position, the motor bundles lie on the lateral and
dorrsal surface of the nerve,
whence springs its motor branches and which ultimately terminate in the
posterior interosseous
nerve. The sensory portion of the trunk, having a more medial and
anterior position, terminates in
the radial nerve. By keeping these facts in mind. torsion may be
prevented to a great degree in
lateroventral sutures of the musculospiral; the motor portion of the
trunk being readily identified
by the position of its motor branches, also by the posterior
interosseous nerve, springing from its
lateral and somewhat dorsal quadrant; the sensory portion of the nerve
being identified by the
absence of branches and by the position of the radial nerve. To make
topographical matching still
more accurate, it should be remembered that the branch to the
brahiolradialis occupies the most
ventral motor position. More
1008
laterally in the nerve
trunk will be found the bundle sending fibers to the long and short
radial
extensors. That portion of the nerve immediately behind these funiculi
ultimately forms the
posterior interosseous trunk.
Torsion
in the posterior interosseous nerve is not so serious an eventuality as
in mixed
nerves, because most of the nerve trunk is composed of motor fibers. In
the supinator region, the
nerve is greatly flattened and its fixation so secure that reasonable
care should prevent torsion. If doubt exists in suturing the
musculospiral nerve as to the location of its sensory segment,
recourse should be had to the electro-anatomic method, in which the
sheath of the upper segment
of the nerve is opened and the bundles subjected to very weak faradic
stimulation. Stimulation of
the sensory bundles will elicit a sensation of tingling or pain
localized in their cutaneous
distribution, while stimulation of a motor bundle will demonstrate the
presence of myosensory
fibers. (See general technique, p. 951.)
SECONDARY SUTURE OF THE MUSCULOSPIRAL NERVE.
Surgery
of the musculospiral nerve has perhaps given more satisfactory end
results than
that of any other nerve, which may be attributed to the following
facts:
1.
The greater number of injuries occur in its lateroventral portion or in
the lateral part of
its dorsal portion, which leaves a comparatively short distance for the
neuraxons to regenerate to
reach their ultimate muscle termination. This feature, facilitating an
earlier restoration of
neuromuscular junctions saves the muscles from that extreme degree of
degeneration
encountered when denervated for a long period of time--a condition
which
can not be avoided in
nerves injured at a great distance from the muscles they supply.
2.
The extensor muscles, supplied by the musculospiral are relatively
large in bulk and the
chance of receiving a greater number of regenerated nerve fibers is
thereby enhanced.
3.
The extensor function of the wrist is accomplished by three extensor
muscles,
supplemented by the common extensors of the fingers, so that defects in
one or more muscles
may not seriously affect extensor function.
4.
Extensor paralysis of the wrist is more generally and earlier
recognized, and lends itself
more readily to splinting than any other types of paralysis: it is
thereby often saved from
prolonged muscle stretching.
A
careful examination of regenerating musculospiral lesions will
demonstrate that,
though the functional end results of musculospiral sutures are more
satisfactory than any other
nerve, from a standpoint of individual muscle function, defective
regeneration is present in the
great majority of musculospiral sutures, and that those muscles which
have a relatively small
bulk and which are innervated at some distance from the point of
lesion, present the same degree
of defective regeneration as observed in other nerves. After
musculospiral suture, radial carpal
extension and brachioradialis action are commonly restored. Less
frequently, however, do we
observe a return of function in the ulnar carpal extensor, and in the
extensor communis
digitorum, while in the extensors of the thumb, index, and little
fingers function is frequently not
regained. Undoubtedly, they enter into that extreme degree of muscle
degeneration common to
muscles of small bulk, long denervated.
1009
INDICATIONS FOR REOPERATION
Before
the musculospiral nerve is subjected to secondary surgical
intervention, certain
facts regarding the failure of regeneration should be definitely
determined:
1. The absence of neuraxon regeneration beyond the point of suture, or
defective or
retarded regeneration through the distal segment.-Tinel's sign,
elicited with the same degree of
intensity below the suture line, as at the suture line, indicates
successful neuraxon regeneration.
The downward progression at the rate of 1 inch per month, of the point
at which formication can
be elicited indicates that regeneration is not retarded, at least in so
far as sensory fibers are concerned. A complete absence or at greatly
diminished reaction of formication below the suture
line indicates absence or defective neuraxon regeneration. After three
months, a failure to elicit
formication below the suture line suggests the absence of regeneration,
particularly if this
reaction is intense at the suture line, though it mav mean only a delay
in regeneration. A decision. therefore, should not be definitely made
until a lapse of six months, at which time absent or
greatly diminished formication in the distal segment of the nerve
should call for secondary
surgical intervention.
2. Torsion
of the nerve trunk- resnlting in the physiologic
rnisplacement of fibers is
another common cause for defective musculospiral regeneration. The
writer has reoperated a case
in which at the original operation, the operator failed to identify the
posterior interosseous
terminal division of the nerve and united the musculospiral trunk
wholly to its radial terminal
division, the lesion being in the region of the internal condyle. In
this case, the long carpal extensor lranch was individually divided and
not repaired. leaving, a complete musculospiral
paralysis below the supinator. Frequently, however, torsion has
occurred during the primmmrv
suture and the radial sensory fibers have passed down the posterior
interosseous nerve and the
motor fibers to the radial nerve: obviously, the misdirected fibers are
physiologically lost. This
misdirection of fibers may occur to any degree and the advisability of
secondary operation for its correction depends entirely upon the extent
of misplacement and the degree of motor function
regained. We must again rely upon Tinel's sign to determine the
position of sensory fibers, and
the musculospiral nerve in its terminal divisions readily lends itself
to convey this information.
Percussion of the nerve trunk below the suture line may give an intense
reaction of formication, but when percussion of the radial nerve (which
normally should convey these sensory fibers)
elicits no tingling or only a slight reaction, the sensory fibers are
absent and have probably been
misdirected, if sufficient time has been allowed for them to reach the
radial trunk. Percussion of
the posterior interosseous on the dorsum of the forearm in the region
of the supinator will
normally give little or no tingling, as it contains mostly motor
fibers. When there has been any
great misdirection of radial fibers through the posterior interosseous
nerve, its percussion will
elicit intense tingling which is localized on the dorsum of the hand.
This localization of tingling
is important as it demonstrates that the sensory fibers in the
posterior interosseous nerve are
definitely radial in origin, it being remembered that in percussing the
musculospiral or the
posterior interosseous nerve, the examiner may elicit reactions in the
external cutaneous
1010
branch of the
musculospiral, in which event the tingling sensation would be localized
along the
dorsal portion of the forearn and not the hand. Frequently, the
presence of sensory fibers in the
extensor muscles on the back of the fore-arm may be denmonstrated by
pressure on their
atrophied bellies, this pressure eliciting a strong formication.
Regenerative
defects, due to misdirection of fibers are unfortunate, in that the
muscles
have been allowed to reach an extreme degree of degeneration because of
their greatly delayed
reinnervation. If muscle degeneration is extreme, recourse must be had
to tendon transplantation
for correction of the motor defect. If, however, these museles have
been preserved and still
respond to galvanic stimulation, secondary suture should be attempted
for the purpose of
correcting torsion. In the secondary operation, the surgeon must not be
guided by anatomically
placed identificationl sutures, but the motor side of each segment of
the nerve trunk should be
identified by the position of its branches or by the electro-anatoinic
method, and the nerve
resutured in a manner which will approximate motor segment to motor
segment. (See
physiologic approximation of the niusculospiral nerve, p. 1007.)
3. Defective muscolospiral regeneration
due to extensive muscular deqeneration.-Percussion of the
musculospiral trunk has demonstrated by Tinel's sign the progressive
downgrowth of neuraxons: percussion of the radial and posterior
interosseous nerves reveals the
presence of radial sensory fibers in the former and their absence in
the latter; therefore, neuraxon
regeneration has probably not been seriously impefed or misdirected.
The return of deep
sensibility in the muscles suggests regeneration of myosensory fibers
which normally
accompany motor fibers, and their presence probably indicates the
regeneration of motor fibers to
the niuscles. The clinical degenerative phenomena continue to persist
in the parallyzed muscles
(complete loss of electrical and mechanical irritability and a total
absence of voluntary motion,
with extreme atrophy). Instances of this kind are by no means rare and
are usually due to
prolonged denervation and ischemia. In this type of regenerative
failure, secondary operations
upon the nerve are absolutely useless and contraindicated. In some
cases, time may effect
improvement, particularly if accompanied with energetic treatment to
improve circulation and
muscle nutrition. In most of these instances, the only hope of
restoring extensor function to the
wrist and fingers lies in tendon transplantation.
TENDON TRANSPLANTATION FOR MUSCULOSPIRAL
PARALYSIS
Probably
no other tendon transplants give results so satisfactory as those
devised for the
drop wrist and fingers in musculospiral paralysis.
In
complete irreparable defects of the musculospiral nerve,
transplantation is indicated for
three conditions, namely, wrist-drop, finger-drop, and thumb-drop. In
low lesions (posterior
interosseous), carpal extension maybe preserved, transplantation being
required only for the
digitis. This maybe the case also in defective musculospiral
regeneration, though more frequently
the disability is confined to the thumb extensors. It is the practice
of some surgeons when
repairing the musculospiral nerve to transplant the pronator radii
teres into the radial extensors,
as this procedure will give immediate
1011
extension of the Wrist
without Sacrificing the function of any muscle or interfering, with the
natural progress of regeneration. We shall therefore consider
individually the transplant necessary
for the correction of each of these various conditions, though one or
all may be corrected during
the course of a single operation.
FOR RESTORATION OF CARPAL EXTENSION
a.
Pronator radii teres into the extensors carpi radialis longior and
brevior to give dorsal
flexion of the wrist.
b.
Divided extensor carpi ulnaris tendon into the flexor carpi ulnaris
prevent radial
deviation of the hand.
TECHNIQUE.
1.
The incision extends along the radial border of the forearm in its
middle third. The line
of cleavage is found between the brachioradialis and the carpal
extensors and deepened to expose
the radius, where the ribbon-like tendon of the pronator teres is found
partially encircling this
bone; this tendon is mobilized and divided at its insertion. The
tendons of the extensors carpi
radialis longior and brevior are now identified, and with thev wrist
held in hyperextension. the
pronator tendon is passed through a slit in these tendons and anchored
after proper tension has
been attained.
2.
To prevent radial deviation of the wrist during extension through
pronator teres action
on the radiocarpal extensors, the ulnar carpal extensor tendon manv be
divided land transplanted
into the flexor carpi ulnaris. Occasionally also in defective
musculospiral regeneration, the
extensor carpi ulnaris fails to regain power, and extension of the
wrist is associated with marked
radial deviation. This transplant is usually very satisfactory for the
correction of this condition.
Frequently the tendon of the flexor carpi ulnaris is used as a
transplant to produice extension of
the third, fourth, and fifth. fingers, and occasionally also the index;
in which case the fleshy part
of thle flexor carpi ulnaris tendon. which is attached to the ulnar
border of this tendon. is
detached and separately transplanted into the extensor carpi ulnaris
tendon, or the extensor carpi
ulnaris tendon may be divided some distance above its insertion and
transplanted into the
detached fleshv fibers of the flexor carpi ulnaris.
FOR RESTORATION OF EXTENSION OF THE DIGITS
a.
Flexor carpi radialis into the extensor ossis metacarpi pollicis,
extensor pollicis ,brevis.
aid ext ensor pollicis longus. and occasionally into the extensors
indices and comlnmunis
tendons of thle index finger.
b.
Palmtiaris longus into the tendon of the long extensor of the thumb,
when the palmaris
is present (about 20) per cent of cases) and when the flexor carpi
radialis is not used for terminal
flexion of the thumb.
c.
Flexor carpi ulnaris into the extensor tendons of the little, ring, and
middle fingers, and
also the index finger when its tendon is not anastomosed to the flexor
carpi radialis.
Inasmuch
as isolated extension of the index finger is important, with extension
of the
thumb, in picking up objects, the writer prefers to use the flexor
carpi radialis for both thumb and
index extension. Some of our most
1012
satisfactory results in
extension of the distal phalanx of the thumb have attended flexor carpi
radialis transplantation into the long extensor in common with the
other extensors of the thumb,
though a separate transplantation of the palmaris longius into this
tendon is a verv satisfactory
procedure.
TECHNIQUE
a.
Through a long incision, extendling from the insertion of the flexor
carpi radialis
tendon to the middle of the forearm on its radio-ventral aspect, the
tendon of the flexor carpi
radialis is exposed, divided at its insertion and freely mobilized to
the upper part of the incision,
care being taken to avoid injury to the radial artery and nerve lying
along its radial border.
b.
A second ventral incision of the same length is made alone the ulnar
border of the
forearm, exposing the ulnar tendon, which is divided at its attachment
and freely mobilized. The
tendon of the flexor carpi ulnaris is split close to its ulnar border,
to which muscle fillers are
attached almost to its insertion. The splitting of the ulnar flexor
tendon in this manner preserves
the insertion of its fleshy fibers to which portion the divided
extensor carpi ulnaris tendon may be
anastomosed. This separation of the flexor carpi ulnaris tendon is
extended to the middle third of
the forearm, where it is lost in the fleshy portion of its belly. The
radial border of the muscle
should. however, be mobilized some distance higher. care being taken to
avoid injury to the ulnar
vessels and nerve which lie below.
c.
A mid-dorsal incision is now carried from the wrist joint to the middle
third of the
forearm, and the fat of the superficial fascia medially and laterally
undermined around both radial
and ulnar borders of the forearm, connecting subcutaneously, on the
radial side, with the
radioventral incision, and, on the ulnar border, with the ventroulnar
incision. The direction of
each tunnel should be arranged in a manner permitting a straight pull
from the upper ventral
surface of the forearm to the dorsal surface of the wrist, by the
transposed extensor tendons. The
mobilized flexor carpi ulnaris tendon is now passed through the tunnel
to the dorsal aspect of the
wrist and passed through as lit in both extensor tendons of the little
finger and the common
extensor tendons of the ring and middle fingers, while the fingers and
wrist are held in complete
extension, which extension must be maintained throughout the operation
and during subsequent
treatment. The undermining of the superficial fascia along the radial
border of the wrist will
expose the tendons of the extensor ossis metacarpi pollicis and the
short extensor of the thumb.
Through the dorsal incision the long extensor of the thumb and both
extensors of the index finger
are identified. The tendon of the flexor carpi radialis is passed
through a slit in these tendons,
while the thumb is in complete extension and abduction, and the index
finger fully extended.
When the proper tension has been obtained, the transplant is fixed to
each tendon by linen
sutures. When it is desired to use the palmaris longus for terminal
extension of the thumb, the
writer prefers mobilizing and dividing the long extensor of the thumb
some distance above the
wrist and transposing it to the ventral surface of the wrist for
anastomosis into the divided tendon
of the palmaris longus; each tendon should be sufficiently mobilized to
permit a pull as nearly
direct as possible from origin to insertion.
1013
After
thorough hemostasis is effected, all incisions are closed, the ventral
prior to the
dorsal, after which the wrist, thumb, and fingers are maintained in
extension by a previously
made long "cock-up" splint; care should be used in preventing any
hyperextension of the
metacarpophalangeal joints. It is often desirable to permit slight
flexion of these joints, which
greatly adds to the comfort of the patient. (Subsequent treatment and
reeducation follow the usual
rules for tendon transplantation.)
TO SUPPLY
EXTENSOR ACTION TO THE THUMB
a.
Flexor carpi radialis into the extensor ossis metacarpi pollicis,
extensor brevis pollicis,
and extensor longus pollicis.
b.
Palmaris longus into the extensor longus pollicis, when extension of
the distal phalanx
of the thumb alone is absent, or when it is deemed advisable to use a
separate tendon for
extending the distal phalanx. The palmaris longus tendon does not
appear to be a suitable
transplant to use for all the extensors of the thumb.
TECHNIQUE.
The
procedure for transplanting the flexor carpi radialis into the
extensors of the thumb or
supplementing this with the palmaris longus to the long extensor of the
thumb varies in no way
from the method described above, except that the mid-dorsal incision
may now be shortened and
made nearer the radial border of the wrist.
MEDIAN NERVE
GENERAL ANATOMY
The
median nerve is formed in the axilla by a union of the anterior
divisions of the outer
and inner cords of the brachial plexus. The outer cord formed by the
fifth, sixth, and seventh
cervical nerves contributes the outer head of the median, while the
inner cord formed by the
eighth cervical all first dorsal supplies the inner head of the median;
the union of the two heads
takes place usually just below the tendon of the pectoralis minor
muscle. The median nerve then
passes down the medial side of the arm in the neurovascular bundle in
close relation to the
axillary and brachial artery. In the axilla the artery will usually be
found lying between the forked
head of the nerve. being crossed lby the inner head before the median
trunk is formed. In the
lower part of the axilla and upper part of the arm the artery lies
immediately behind the nerve. As
it progresses down the arm the artery first lies medial to the nerve,
but toward the middle of the
arm the relation is reversed, the artery crossing to the lateral side.
In the upper part of the arm the
median nerve is overlapped by the coracobrachialis muscle and the
medial border of the biceps.
In the lower half of the arm the nerve lies upon the brachillis
antictus. becoming superficial as it
assumes a more anterior position entering the antecubital fossa. In the
antecubital fossa the nerve
passes under the bicipital fascia and begins its course down the
forearm; passing beneath the,
superficial or humeral head of the pronator radii teres, it enters its
deep position in the forearm by
passing under the tendinous arch of the flexor sublimis
1014
digitorum. Crossing the
ulnar artery it follows the under surface of the sublimis digitorum,
lying
upon the flexor proftndus. As it approaches the wrist the nerve again
becomes superficial, lying
in this region under the tendon of the palmaris longus medial to the
flexor carpi radialis and
lateral to the sublimis tendons. It passes below the anterior annular
ligament; and in the palm,
lying under the palmar fascia, it remains lateral to the sublimis
tendons, where it divides into its
terminal digital branches.
BRANCHES
The
only branch given off by the median nerve in the arm is in the lower
portion of the
lower third, where a small branch supplies the elbow joint, though,
occasionally, the branches to
the pronator radii teres arise in this region. There are, however, many
instances in which the
median in the arm communicates in various degrees with the
musculocutaneous. (See
musculocutaneous nerve, p. 993.)
As
the median nerve enters the antecubital fossa it gives off branches,
usually three in
number, to the pronator radii teres. Occasionally the three branches
may leave the main median
trunk in a single sheath, dividing after leaving the parent nerve. The
next branches given off are
to the palmaris longus, flexor carpi radialis, and flexor sublimis
digitorum, in the order named.
Occasionally, however, at this point a single large motor branch is
given off from the median,
supplying all the median innervated extrinsic muscles. In such cases
the branches to the palmaris
longus, flexor carpi radialis, and flexor sublimis digitorum first
leave this motor portion. The
remainder of this trunk, carrying branches to the deep muscles, is
commonly known as the
anterior or volar interosseous nerve and is accompanied in its course
down the arm by the
anterior interosseous artery. This branch occupies a position somewhat
deeper than the main
trunk of the median nerve, lying in the cleft between the flexor
profundus digitorum and the
flexor longus pollicis, giving branches to these muscles in its earlier
course and terminating in
the wrist by supplying the pronator quadratus muscle and sending
filaments to the radioulnar
articulation and the wrist joint. The motor branches to the extrinsic
muscles. however, may leave
the parent trunk with many variations, superficially arising from both
sides of the median trunk.
When, however, these branches are followed a short distance up the
parent trunk it will be found
that they arise from those funiculi which occupy the medial half of the
nerve, the most ventral
fibers supplying the pronator radii teres. Medial and slightly
posterior to the pronator funiculi lie
the fibers to the palmaris longus, flexor carpi radialis. and flexor
sublimis digitorum, while the
funiculi to the flexor profundus digitorum and flexor longus pollicis
encroach upon the posterior
surface of the nerve. All these motor branches, however, are located on
the medial side of the
nerve and may be followed up the nerve trunk by an intraneural
dissection for some distance,
occasionally as high as the middle of the arm. Often the branches
supplying the deep muscles
(volar interosseous nerve) leave the median trunk as an individual
lower lranch. Just above the
wrist the median nerve gives off a sensory palmar cutaneous biranch,
which passes above the
annular ligament
1015
After passing into
the palin the median gives off motor branches from its radial side to
supply the opponens, abductor, and superficial head of the flexor
brevis pollicis. In the region of
the superficial palinar arch the nerve becomes enlarged and flattened,
dividing into two branches,
which in turn subdivide into five terminal cutaneous sensory branches.
These branches. shortly
after their origin andl occasionally before, give off motor branches to
the first and second
lumbricales muscles.
SURGERY
IN THE ARM
Axillary
portion.- Lesions involving the median nerve in the axilla are
seldom isolated
lesions; they are usually combined with injuries to contiguous elements
in the neurovascular
bundle, so that from a surgical stand point lesions of the median nerve
in the axilla are treated as
lower plexus lesions. (See lower plexus lesions, p. 984.)
In
the arm.- Lesions of the me(lian nerve in the arm are seldom
confined to this nerve.
The close proximity of the ulnar trunk, the brachial artery. the
basilic vein, and the internal cut
aneous nerve makes combined lesions more frequent in the upper
two-thirds of the arm, while in
the lower third the ulnar and internal cutaneous are frequently spared.
Exposure
of the median nerve in the arm is best accomplished with the arm in
abduction
and outward rotation. The incision follows the medial border of the
coracobrachialis above and
the biceps below. These structures somewhat overlap the nerve along its
liumeral course. In the
upper part of the arm the nerve will be found lvina lateral and
anterior to the artery: below the
mid portion it crosses the artery and lies on the medial side. The vein
and artery are so commonlv
involved in median injuries in this location that special care should
be used in dealing with these
structures to prevent undue bleeding, particularly if the lesion is
associated with much scar tissue.
It is always essential that these vascular structures be isolated above
and below the field of scar
tissue invasion. With the control of these vascular channels, the
surgeon is usually master of the
situation and the dissection is greatly facilitated.
In
the arm the median nerve gives off no important branches: however,
often it
communicates by various tvpes of anomalies with the musculocutaneois.
explaining certain
median lesions in which, at operation. the nerve is found to be
completely divided. though the
clinical examination reveals incomplete median anesthesia, or the
retention of motor power in the
median muscles. In making a diagnosis of partial median injury,
anomalous communications
between the median and musculocutaneous nerves should always be borne
in mind. Electrical
stimulation of the median nerve in suspected partial lesions will
produce contraction in the
unparalyzed median muscles, if it be a true partial lesion. If this
stimulation fails to elicit
contraction in these muscles, stimulation of the musculocutaneous,
which is easily accomplished
by identifying its trunk on the dorsal surface of the biceps, will
indicate the nature of the innervation, if it be due to a median and
musculocutaneous anomaly. Retained
1016
function, motor or
sensory, when the median trunk shows complete anatomical division, is
usually due to median fibers passing down the musculocutaneous trunk
and joining the median
below the lesion. This refers entirely to the extrinsic muscles; the
intrinsic hand muscles,
particularly the superficial head of the flexor brevis pollicis may not
be paralyzed in complete
median paralysis, in which case it is probably wholly innervated by
ulnar branches.
When
median lesions in the arm are associated with irritative or marked
vasomotor
phenomena, particular attention should be given to complete isolation
and decortication of the
brachial artery (periarterial sympathetectomy, after the method of
Leriche). In the writer's
experience this has occasionally relieved painful nerve syndromes where
all other methods have
failed. In median causalgia or severe median irritative lesions without
anatomic division of the
nerve an internal neurolysis is also indicated if the median trunk
presents any evidence of scar
induration upon palpation.
The
prevention of torsion of the median trunk in the arm is best
accomplished by the use
of accurately placed identification sutures before the nerve has been
completely isolated from its
bed. The anatomic method of fascicular identification, by relying upon
motor branches, can be
utilized only in low lesions in the region of the internal condyle,
where a branch is given off to
the pronator teres. This branch, however, may be followed some distance
up the median trunk as
a well identified funiculus. Its intraneural localization will reveal
the anterior and medial portion
of the nerve trunk in this region, it being the most anterior of the
motor bundles. The
determination of funicular topography above the branches to the
pronator radii teres is possible
only by the electro-anatomic method, which will serve, if properly
conducted, to identify the
position of the sensory bundles, which lie in the lateral aspect of the
median trunk. When
secondary sutures are indicated, because of torsion during the original
suture, identification
sutures are of no value and resuturing must be guided by localization
obtained by the electro-anatomic method of identification.
IN THE ANTECUBITAL FOSSA AND UPPER TWO-THIRDS
OF THE FOREAR'M
The
position of the arm for exposure of the median nerve in this region is
one of
abduction and external rotation, with the forearm in complete
supination.
The
median nerve, after entering the antecubital fossa at the bend of the
elbow assumes a
very deep position through the upper two-thirds of the forearm, though
it becomes more
superficial as it approaches the wrist. Exposure of the nerve in the
forearm is greatly facilitated
by a clear understanding of certain anatomic relationships. The
operator attempting this exposure
should avail himself of an opportunity to become familiar with these
points, by recourse to the
dissecting room, if his visualization of this regional anatomy is at
all obscured. The following
anatomic points require special consideration: (1) The anatomy of the
antecubital fossa; (2) the
relation of the pronator radii teres to the median nerve; its insertion
in the radius and its relation
to the flexor carpi radialis; (3) the radial origin of the flexor
sublimis digitorum and the arching
fibers of this origin, which surround the nerve; (4) the relation of
the median nerve in the wrist to
the tendons of the palmaris longus and flexor carpi radialis.
1017
The
antecubital fossa is a triangular space, the base above lbeing
formed by an imaginary
line connecting the humeral condyles. The medial boundary is formed by
the lateral edge of the
pronator radii teres, while the lateral border is formed by the medial
edge of the brachioradialis.
The biceps tendon passes through the lateral side of the fossa. Both
nerve and artery rest upon
the floor of the fossa which is formed by the brachialis anticus. In
the lower part of the fossa, the
brachial artery divides into its radial and ulnar portions. The fossa
is covered by the deep fascia
and in its lower part by that thickened portion of the deep fascia
which constitutes the bicipital
fascia. Exposure of the nerve in or just above the antecubital fossa is
facillitated by identifying
the medial border of the biceps and its tendon; both the nerve and
artery lie to its medial side. A
tape placed around the artery in the upper part of the incision will
facilitate its control in case of
emergency, while making a scar tissue dissection, the vein being
controlled from below.
The
pronator radii teres passes from the internal humeral condyle
diagonally across the
forearm to be inserted in the middle of the radius by a long flat
tendon which partially encircles
the bone. This muscle forms the lower medial boundary of the
antecubital fossa. It is composed
of two heads, a large superficial head taking origin from the internal
condyle in common with the
other superficial mucles. The deep head of the pronator arises from the
ulna and is very much
FIG. 176.- Exposure
of
median nerve in lower
arm and upper forearm, showing its relation to the brachial artery and
biceps; both artery and nerve are covered by the bicipital fascia A
Median nerve; B, brachial artery; C, branch to
pronator teres; D, radial artery; E, bicipital fascia; F, internal
intermuscular septum; G, ulnar nerve; H, brachial
epicondyle; I, deep fascia covering superficial flexors
smaller than the
superficial head. The median nerve passes in the cleft between the two
heads of
the pronator. The radial artery, after the division of the brachial,
passes to the radial side of the
forearm above the pronator teres, while the ulnar artery directed to
the ulnar side, passes beneath
the deep head of the pronator and is thus separated from the median
nerve. The lower or medial
border of the pronator has a direct fascial attachment with its
adjoining muscle, the flexor carpi
radialis. The insertion of the pronator into the radius is covered by
the brachioradialis, and along
the under surface of the latter passes the radial nerve. The median
nerve in the antecubital fossa
1018
and under the
superficial head of the pronator gives off its important motor branches
to the
extrinsic muscles. In this region great care must be used for the
preservation of these branches. Their exit from the parent trunk may
be, superficially, from either side. Their deep origin within the
median trunk is from the medial portion of the nerve; the lateral being
the sensory portion. The branches to the pronator, the flexor carpi
radialis, and
FIG. 177.- A, Exposure of
median nerve in the
antecubital fossa; bicipital fascia divided, pronator teres mobilized
from its attachment to flexor carpi radialis. B, Numeral head of
pronator teres divided and retracted, exposing
branches of the median nerve in this region. Deep head of pronator is seen passing below the
median
nerve and crossing the ulnar artery. Branches of the median nerve to
the forearm muscles are shown springing from its medial side. A, Median
nerve; B, brachial artery; C, branches to
pronator teres; D, motor branches to superficial flexors; E,
medial
epicondyle; F, pronator teres, deep head; G,
pronator teres, superficial head; H, bicipital fascia; I, ulnar artery;
J, radial artery; K, motor branches to deep
flexors; L, flexor sublimis digitorum, split; M, flexor carpi
radialis
the palmaris longus are
usually given off higher than the branches to the deep muscles.
Exposure
of the nerve under the pronator is best accomplished by dividing its
tendon near
its insertion into the radius, care being taken to avoid the radial
nerve and artery which pass over
the tendon in this region. The radial artery must be mobilized and
freed from this muscle, which
will necessitate the ligation
1019
tion of several small
branches. After the tendon of the pronator has been divided, this
muscle
may be reflected toward the medial side of the forearm, exposing its
under surface and deep head
which will be found passing around the median nerve. After the division
of the pronator tendon,
its medially adjacent muscle, the flexor carpi radialis, may be
partially retracted toward the
medial side of the forearm, exposing the flexor sublimis digitorum and
its tendinous arch, which
in reality is the keynote of the situation.
The
flexor sublimis digiforum.-The points to be remembered in
connection with this
muscle are that it covers the median nerve, which passes along its
posterior surface; it arises
from four heads, the first three of which are from the ulna side and
more or less in common with
the superficial muscles: the fourth head is from the radius, and the
fibers radiating between the
radial and humeral heads form an arch under which the median nerve and
ulnar artery pass. The
radial head should be carefully divided and the muscle gently retracted
toward the medial side of
the forearm with the pronator. This procedure will give adequate
exposure of the median nerve throughout
its deep portion.
FIG. 178.- Intraneural dissection of median branches in
the forearm,
showing their origin from the medial trunk.
Highest branches to be given off are to the pronator, whose branches
originate from the most ventral portion of the
motor quadrant. The volar interosseous likewise arises from the medial
side of the median trunk, though occupying
a more dorsal position than the bundles to the superficial muscles. A,
Median nerve; B, branch to pronator teres; C,
branches to superficial fleors; D,branch to deep flexors; E, branch to
pronator quadratus; F, division of brachial
artery; G. ulnar artery; H, pronator teres, superficial head; I,
pronator teres, deep head: J, flexor carpi radialis K,
palmaris longus; L, portion of flexor sublimis digitorum; M, flexor
carpi ulnaris
The
median nerve above the wrist occupies a relatively superficial
position, lying beneath
and to the radial or lateral side of the palmaris longus tendon; in the
absence of this tendon, the
nerve will be found just internal to the tendon of the flexor carpi
radialis. If the forearm has
suffered extensive scar invasion, with destruction of tendons, etc., it
may be necessary to first
locate the nerve in this position at the wrist.
1020
EXPOSURE IN THE
FOREARM
Exposure
of the median nerve in the forearm is accomplished by a straight
incision of the
dlesired length, extending from the medial side of the biceps just
above the antecubital fossa, in
a line toward the insertion of the flexorcarpi radialis tendon. In most
instances, it is necessary to
extend the incision from the upper part of the antecubital fossa to the
lower third of the forearm.
In the upper part of this incision the median basilic vein is exposed
and divided between forceps.
At a point corresponding to the insertion of the biceps tendon, the
sensory portion of the
musculocutaneous nerve is usually encountered in the superficial fascia
and its fibers preserved if
possible. In the upper part of the incision the contents of the
antecubital fossa are exposed by
dividing the deep and bicipital fascia: the median nerve and the
brachial artery are now identified
as they pass along the medial side of the biceps tendon, the artery
lying between the nerve and
the tendon. The median nerve mav now he followed to where it passes
below the superficial head
of the pronator. In the antecubital fossa, great care should be
exercised in avoiding injury to the
motor branches to the pronator and the extrinsic muscles. If this
exposure is not sufficient to
identify the lower segment of the nerve, it must be approached in the
lower third of the forearm
and followed upward. To permit a lower exposure, the skin incision is
extended to the lower
third of the arm and the deep fascia divided, exposing the tendon of
the flexor carpi radialis, and
the median nerve located below the tendon. At the junction of the
middle and lower third of the
forearm, the median nerve is somewhat deeper than at the wrist, and it
may be exposed by
retracting the tendon of the flexor carpi radialis laterally. exposing
below the aponeurotic medial
edge of the flexor longus pollicis: the nerve will now be found in the
cleft between the latter
muscle and the flexor sublimis digitorum. The median nerve, having been
exposed in the upper
and lower thirds of the forearm, will require exposure in its middle
third, where it is deeply
placed between the sublimis and profundus digitorum muscles. Exposure
of the median nerve in
the middle third of the forearm is the most difficult step in the
operation, and is accomplished by
dividing the tendon of insertion of the pronator radii teres and
reflecting this muscle with the
flexor carpi radialis medially, exposing the radial head of the flexor
sublimis digitorum, which in
turn is divided and also retracted medially; the nerve is identified as
it lies on the ventral surface
of the profundus dligitorum. If precaution is not taken, serious
trouble may be experienced in this
exposure through injury to arterial twigs leaving the radial artery.
The brachial artery, before it
divides into its terminal radial and ulnar divisions in the antecubital
fossi, may be secured for
control by the passage of tape around the vessel, which may be
tightened at will. The radial artery
passes over the tendon of the pronator radii teres near its insertion
in the radius and passes down
the forearm undercover of the brachioradialis, accompanied by the
radial nerve. In its course
down the forearm, the radial artery gives off numerous twigs which must
be ligated before
attempting division and retraction of the pronator. After the radial
artery has been mobilized, it is
retracted mediallv with the brachioraidialis, exposing the flattened
tendon of the pronator, which
is divided, and the muscle belly reflected. The radial or lateral edge
of the flexor earpi raidialis is
freed
1021
and retracted with the
pronator, exposing the ventral surface of the flexor sublimis
digitorum. With the reflection and exposure of the under surface of the
pronator, the median nerve will be
found passing between its two heads, the deep head of this muscle being
but little larger than the
median trunk--it may be divided to permit mobilization of the nerve.
The median nerve may now
be followed to where it disappears below the arched fibers connecting
the two heads of the flexor
sublimis digitorum. The radial head of this muscle is small and
fibrous, and should be divided to
permit its medial reflection, which is readily accomplished after
freeing its radial border: the
median nerve is now completely exposed throughout the forearm. Its
important motor branches
are given off in the lower part of the antecubital fossa, in the middle
third of the forearm beneath
the pronator and the early part of its course below the sublimis. In
making this exposure, great
care should be used in preventing injurN to these branches. The
identification of branches
should proceed from above downward, resorting to electrical stimulation
to confirm identification, if branches are intact. (See general anatomy
of the median nerve, p. 1013.)
PHYSIOLOGIC
APPROXIMATION IN THE UPPER TWO-THIRDS OF THE
FOREARM
Before
complete dissection of the nerve is attempted, the center of its
ventral quadrant
should be marked with identification sutures to be used in subsequent
alignment during
approximation. In approximation of the median nerve
FIG. 179.- Median
nerve lesion in middle third
of in the upper forearm, it is essential forearm; nerve exposed
above and below lesion and that the branches to the pronator and
marked with identification sutures. In this in-long flexor muscles be
identified and stance the nerve is exposed below the pronator teres by
dividing the flexor
sublimis digitorum, A, Branch to pronator teres; B, pronator teres; C,
bicipital fascia; D, flexor carpi radialis; E,
median nerve, upper segment; F, flexor sublimis digitorum, split; G,
median nerve, lower segment: H, median nerve;
I, brachial artery; J, radial artery; K, brachioradialis
in the upper forearm, it
is essential that the branches to the pronator teres, lesions above
this
point will probably involve most of these branches before they have
left the median trunk. It is
essential, therefore, that the medial side of the nerve trunk be
accurately identified in both
proximal and distal ends of the divided nerve, as the bundles forming
the motor branches are
located in this portion of the median trunk, the fibers to the pronator
being more
1022
ventral than those to
the palmaris longus, flexor carpi radialis, and sublimis digitorum.
Often in
this region a dissection of the median trunk will reveal all its motor
branches incorporated in an
individual sheath, lying along the medial side of the nerve. In such
instances, individual
approximation of the motor segment is possible.
FIG. 180.- Transposition
of
median nerve to a
plane superficial to superficial head of pronator radii teres.
Intraneural
mobilization of branches. Continuity defect may now be overcome by
flexion-relaxation of elbow. A, Median
nerve; B, motor branches, mobilized; C, brachial Artery; D, radial
artery; E, brachioradialis; F. bicipital fascia; G,
pronator teres; H, flexor fascia; I, sublimis digitorum
FIG. 181.- Median nerve
transposed to
overcome median defect and sutured; nerve now passes superficial to
pronator radii terres and below flexor carpi radialis. Nerve sheath
partly closed. A. Median nerve; B, brachial
artery, C, radial artery; D. Pronator teres; E. Motor branches; F,
brachialis anticus; G, biceps; H, bicipital fascia; I,
brachioradialis; J, flexor carpi radialis; K, flexor sublimis digitorum
Lesions
of the median trunk below the pronator seldom involve all its motor
branches,
though in extensive lesions many of them may suffer individual injury.
The motor branches to
the profundus digitorum, flexor longus pollicis, and pronator quadratus
may be given off from
the medial side of the nerve below the flexor sublimis digitoruni, as
individual branches,
but more often they
1023
leave the nerve trunk as
the volar interosseous nerve in the region of the pronator, and
occasionally it is possible to effect individual suture of this rather
large branch, which will be
found passing down the cleft between the profundus digitorum and the
flexor longus pollicis,
accompanied by the volar interosseous artery.
After
the motor branches to the extrinsic muscles have left the median trunk,
its content
in motor fibers consists solely of those to the median intrinsic hand
muscles, which lie in the
dorsal quadrant of the nerve. Though the intrinsic hand muscles seldom
recover function after a
long period of denervation, the operator should exert just as great
care in preventing torsion of
the median trunk in this region, for a disturbance of its sensory
pattern will result in defective
tactile localization, which will greatly diminish the functional
usefulness of the digits.
CONTINUITY DEFECTS
If
the continuity defect of the nerve be too great to be overcome by
primary stretching and
flexion-relaxation of the elbow and wrist joints, transposition is
indicated, in which the median
nerve is transposed to a position above the superficial head of the
pronator teres. In order to make
this procedure available, the motor branches must be gently mobilized
by an intraneural
dissectionof the nerve trunk after its sheath is opened; failure to do
so will result in their
destruction. Most of these motor branches may be readily isolated from
the parent trunk to some
distance above the medial condyle. The median nerve in its transposed
position passes along the
radial border of the flexor carpiradialis above the pronator teres. A
transposition of this nature
will usually shorten the distance of a defect from 4 to 7 cm. during
forearm flexion. If, after
transposition, it still remains impossible to approximate the nerve
ends, the unsectioned ends of
the nerve should be sutured for secondary stretching and resort made to
the two-stage operation,
rather than to grafting. Failing in this, the surgeon's only recourse
will probably be to grafting, for
which the radial nerve, lying just under the exposed brachioradialis
may be used to advantage.
MEDIAN LESIONS AT THE WRIST AND COMBINED
TENDON INJURIES
Most
lesions involving the median nerve at the wrist are combined with
lesions of the
flexor tendons. It is therefore necessary to exercise great care in
these dissections, for the normal
anatomic relationships are frequently lost with the destruction of the
tendons. It is advisable
always to first identify and isolate the median nerve to prevent
secondary injury to this structure
during the dissection of the tendons.
EXPOSURE AT THE
WRIST
It
is essential to identify the tendon of the palmaris longus, if this
muscle be present;
likewise the tendon of the flexor carpi radialis. The median nerve
passes under the annular
ligament just below the palmaris longus tendon, to the ulnar side of
the flexor carpi radialis
tendon and to the radial side of the
1024
sublimis tendon;
identification of these structures will usually facilitate exposure of
the nerve. If
the lesion is low, it may be necessary to divide the annular ligament
and palmar fascia, exposing
the nerve in the palm where it may be readily identified as it passes
along the radial side of the
sublimis tendons.
If
difficulty is experienced in locating the upper end of the nerve, the
flexor carpi radialis
tendon should be followed up, exposing the line of cleavage between the
tendon of the flexor
sublimis digitorum and the flexor longus pollicis. Retraction of the
flexor sublimis digitorum
will usually reveal the nerve on the under surface of this muscle. If
this exposure fails to reveal
the location of the nerve, it may be necessary to locate it as it
passes under the pronator radii
teres and the tendinous arch of origin between the heads of the flexor
sublimis digitorum, as in
middle forearm exposures. The palmar cutaneous branch is given off from
the anterior surface of
the median, a few centimeters above the annular ligament; in the
presence of much scar tissue its identification is extremely difficult
and when possible its repair should be attempted. After the
median nerve has been located and before it has been completely
isolated from its bed, it should
be carefully marked with identification sutures, as in the lower third
of the forearm funicular
topography can not be determined by branch identification.
Occasionally, advantage may be taken of the fact that the anterior
surface of the nerve is frequently marked by the comes nervi
mediana artery passing along its sheath; this artery is quite large and
its presence may facilitate
surface identification. Electro-anatomic identification at the wrist is
of but little value, as the
greater bulk of the nerve in this region consists of sensory fibers,
its only motor fibers being those to certain intrinsic hand muscles
which are located in the dorsal part of the nerve trunk.
Even though the nerve is mostly sensory in this region, it is necessary
to prevent torsion during
suture, for sensory fibers normally innervating one finger may be
directed to another, resulting in
confusion of tactile localization. The writer has observed an officer
whose median nerve was
sutured at the wrist; after four years there was a complete return of
al forms of sensation, though
touch on the third finger was always localized in the thumb, which
inhibited to a considerable
extent manipulative dexterity in handling small objects. 'This officer
is gradually becoming
accustomed to this sensory perversion, by psychological reversion and
experience. This case serves to illustrate the confusion arising from
the distortion of sensory fibers during suture.
REPAIR OF TENDONS IN COMBINED NERVE AND
TENDON LESIONS
After
the nerve has been properly identified and isolated, and before suture
or the
resection of scar tissue from its ends, the injured tendons must
receive careful attention. They
should be completely isolated from the scar tissue and every vestige of
scar carefully removed
with as little trauma as possible. Tendons completely divided should be
resutured and when this
is impossible, because of extensive destruction, they should be united
to neighboring tendons
having like function. The surgeon should always endeavor, in
reconstructive surgery of the wrist,
where distortion of the original tendon
1025
pattern is necessary, to
provide tendon anastomoses of a physiologic type for both ends of each
divided tendon. After the tendons have been properly cared for and
perfect hemostasis assured,
the ends of the divided nerve may be prepared and approximated, with
due respect to physiologic
alignment. Flexion of the wrist will assist in facilitating
approximation, though when this is
necessary in the presence of combined tendon lesions, flexion of the
fingers is not advisable.
Early gentle passive movements are essential to success in combined
nerve and tendon lesions of
the wrist, and these passive movements should be persistently
encouraged throughout the healing
process, until such a time as they may be replaced by active movements,
endeavoring always to
simulate the full range of normal coordinated hand and finger
movements; the importance of
these passive exercises can not be too strongly emphasized; they should
be begun not later than
48 hours after the operation.
SURGERY OF THE MEDIAN NERVE IN THE HAND
Only
occasionally is it possible to effect suture of the terminal digital
branches of the
median nerve. In the presence of extensive scar tissue it will probably
be found impossible,
though small incised lesions may lend themselves to successful repair.
The writer has on two
occasions been successful in effecting satisfactory suture of the
median nerve in the palm where
the injury was caused by a penetrating gunshot wound. In one instance,
the suture was effected
just before the nerve divided into its terminal digital branches. In
the other instance, the division
was about the point where the terminal branches were given off. In this
case the individual
branches were collected and united to the end of the trunk, apparently
without torsion, as
regeneration resulted in accurate tactile localization.
Occasionally
the median nerve in the hand may be incorporated in scar tissue,
producing
an irritative syndrome, with retained sensation. Neurolysis will
usually give relief. Incised
wounds of the fingers occasionally present sensitive neuromas, which
are a source of constant
annoyance. In such instances the nerve should be exposed and sutured if
possible; when approximation fails, the neuroma should be excised, the
end of the branch strongly litigated and,
proximal to the ligature, injected with pure alcohol.
EXPOSURE IN THE PALM
Exposure
of the median nerve in the palm is accomplished by an incision
extending from
the insertion of the palmaris longus tendon into the palmar fascia to a
point corresponding to the
interval between the index and ring fingers. The incision is carried
through the integument and
fat of the superficial fascia, exposing the palmar fascia, which is
divided in the line of the
cutaneous incision. The long flexor tendons are identified, and at the
base of the palm the median
nerve will be found lying to the radial side of these tendons. Shortly
after the nerve passes under
the annular ligament branches are given off. which pass radially to
innervate the superficial
thenar muscles, and supply sensation to the thumb. It is highly
essential that these branches be
preserved as they control to a great extent the opposing function of
the thumb.
1026
As
the median nerve progresses through the palm it attains a position
superficial to the
flexor tendons, but passes below the superficial palmar arch. Proximal
to the
metacarpophalangeal joints the nerve divides into its terminal
branches, where it is enlarged,
flattened, and, in contrast to the fatty tissue in which it lies, has a
somewhat pinkish color. The
median divides into five terminal branches. supplying sensation to the
first three and radial half
of the fourth fingers. These branches may readily be identified, as
they lie imbedded in the deep palmar fat, superficial to the flexor
tendons, providing the operator has achieved
adequate hemostasis, which is highly essential in such dissections and
which in the writer's experience has been satisfactorily accomplished
only by the use of infiltration anesthesia, containing a small amount
of active adrenalin to blanch the tissues.
IRREPARABLE LESIONS
Irreparable
median nerve lesions present a serious problem. Though the action of
extrinsic muscles be retained and finger and thumb movements fairly
well preserved, the loss of sensation in the first three fingers is a
serious handicap and every endeavor should be made to
restore, if possible, some type of sensation in the median distribution
to the fingers. The surgeon
may have recourse to autogenous grafts and may utilize a segment
removed from the radial
nerve. If this seems impractical,
FIG. 182.- Branches of
median nerve in hand.
A, Palmar fascia, cut edge; B, annular ligament; C, median branches to
thenar muscles; D, branches to lumbricales; E, thenar formation, F,
digital sensory branches; G, palinaris longus
tendon
because of
extensive scar tissue formation, the procedure of niting the radial to
the median,
recommeded and practiced by Harris, may be considered. In this
procedure, the distal end of the
radial nerve is divided at a point where it may be brought in contact
with the lower segment of
the median, to which it is anastomosed, for the purpose of supplying
the anesthetic digits with a
radial sensory innervation. It must be remembered. however, that this
sensation is localized in the
normal radial sensory area. It may correct trophic disturbance and
serve in the prevention of
injuries to the digits, but the function of tactile localization, so
necessary to manual dexterity, is lacking.
1027
In
median lesions with extensive continuity defects, the severity of the
lesion to the
surrounding parts makes the possibility of successful grafting rather
remote; the functional
disability remaining after radial anastomosis renders this operation a
procedure of last resort. It
behooves the surgeon, therefore, to exert every effort to procure
end-to-end suture of the median,
using the two-stage operation, and if necessary, extending the
dissection high up in the arm, or
even in the axilla. If there also exists a combined ulnar lesion with
paralysis of the ulnar intrinsic
hand muscles, which has existed beyond one year, and the proximal end
of the ulnar is in a
position where it may be brought in contact with the distal end of the
median, the ulnar may be
anastomosed into the median. This procedure will give, perhaps, better
functional results than
radial anastomosis, though it precludes the possibility of subsequent
ulnar regeneration with a
continuation of complete anesthesia in the little finger, and
interossei paralysis. After one year, it
is extremely doubtful whether interossei regeneration would ever occur,
and the little finger, if
necessary, may be amputated, if trophic changes and traumatic insults
to his anesthetic member
should necessitate such a procedure.
TENDON TRANSPLANTATION FOR PARALYSIS OF THE
MEDIAN NERVE
If
it is possible to provide sensation to the fingers and hand, a varying
degree of
functional usefulness may be restored, even though there exists a
complete paralysis of all
median innervated muscles. The flexor profundus digitorum, supplied by
the ulnar, provides
flexion of the fourth and fifth fingers, and frequently the middle
finger. The problem, therefore,
consists in restoring flexion and opposition to the thumb, and flexion
to the index finger and
occasionally the middle. Frequently the ulnar supplies the superficial
head of the short flexor of
the thumb, or a slight change in the insertion of this muscle
diminishes greatly the disability of
opponens paralysis, so that in a certain number of cases opposing thumb
function is fairly well
preserved and tendon transplantation is required only to restore
function in the long flexors of the
thumb and index finger.
In
those cases of median paralysis in which the thumb is displaced
laterally and call not
be made to assume its normal opposed position, an arthrodesis of the
carpometacarpal joint in a
position of opposition and abduction with an angle of about 600 between
the first and second
metacarpals. as recommended by Baldwin, is a very satisfactory
procedure. A fibrous ankylosis
probably gives better results after this artbrodesis than a solid bony
ankylosis. Ney has obtained
very satisfactory opponens function of the thumb by tendon
transplantation, in which the short
extensor of the thumb is divided at the wrist and freed to its
insertion. The palmaris longus is
then exposed and divided just above the annular ligament. The short
extensor of the thumb is
now passed through a tunnel under the subcutaneous fat of the thenar
eminence to the palm of the
hand, and after being passed under the annular ligament is transplanted
into the tendon of the
palmaris longus, or, the latter muscle being absent, into the flexor
carpi radialis. If the flexor
carpiradialis and palmaris longus are paralyzed, it may be inserted
into the extensor
1028
carpi radialis tendon or the flexor carpi ulnaris tendon, which are
being utilized to restore flexion
to the distal phalanx of the thumb and the index finger. This procedure
for obtaining opponens
action finds its greatest usefulness in combined median and ulnar
lesions with complete intrinsic
hand muscle paralysis, under which subject the technique is described
in detail.
FOR PARALYSIS OF THE LONG FLEXOR OF THE THUMB
AND THE FLEXORS OF THE INDEX FINGER
An
incision is made about 5 cm. long from the base of the metacarpo-carpal
joint of the
thumb along the radial border of the forearm, following the radial edge
of the flexor carpi
radialis. Undermining this incision medially, the deep flexor tendons
are exposed and the long
flexor of the thumb located just below the tendon of the flexor carpi
radialis. Retraction of the
edges of the wound laterally will expose the tendon of the extensor
ossis metacarpi pollicis
which is divided near its insertion into the base of the first
metacarpal bone. The radial artery and
its several branches lie in the space between these tendons and may
require ligation. After the
tendon of the extensor ossis metacarpi pollicis has been freed and
divided it is anastomosed to
the divided end of the flexor longus pollicis, under sufficient tension
to insure flexion of the
distal phalanx of the thumb. The flexor tendons to the index finger may
now be identified and
freed. An incision on the dorsum of the wrist over the tendon of the
extensor carpi radialis is
made from its insertion some distance up the forearm. The tendon of the
radial carpal extensor is divided, carefully mobilized, and passed
through a subcutaneous tunnel from the dorsum of the
forearm to the incision on the ventral surface and transplanted into
both flexor tendons of the
index finger. During this procedure the wrist is held in flexion and
the index finger about half
flexed. It is essential in the postoperative treatment that early
passive movements be instituted to prevent adhesions, which would tend
to keep the index finger in permanent flexion. In our
experience these procedures have given perhaps the best results, though
very satisfactory results
have followed a transplantation of the index flexor tendons into the
flexor carpi ulnaris.
ULNAR NERVE
GENERAL ANATOMY
The
ulnar nerve arises from the inner cord of the brachial plexus in common
with the
inner head of the median and the internal and lesser internal cutaneous
nerves, most of its fibers
being derived from the anterior divisions of the eighth cervical and
first thoracic roots. The nerve
lies medial to the inner head of the median and lateral to the internal
cutaneous. In passing
through the axilla and the upper two-thirds of the arm, the ulnar
occupies a position medial to the
artery and the median nerve in the neurovascular bundle. In the lower
part of the middle third of
the arm the nerve leaves the neurovascular bundle, and penetrating the
internal intermuscular
septum follows a posterior course to a position posterior to the
internal humeral condyle, lying in
close relation to the posterior surface of the internal intermuscular
septum, and crossing the fibers
of the medial head of the triceps, which|
1029
arise from this portion
of the septum. In this region the ulnar nerve is accompanied by the
inferior
profunda artery, which usually lies on its ventral surface. The
profunda artery in the region of the
internal humeral condyle anastomoses freely, as dloes its vene comites,
with the posterior ulnar
recurrent artery and veins. Behind the medial condyle the ulnar nerve
occupies a very superficial
position and is covered by a thick, aponeurotic fascia, which extends
from the condvle to the
olecranon. The nerve enters the forearm by passing under an aponeurotic
arch, connecting the
humeral and ulnar leads of the flexor carpi ulnaris, and continues its
course down the forearm, covered by the belly of this muscle and lying
on the profundus digitorun. In the upper third of
the forearm the ulnar nerve is separated some distance from the ulnar
artery, while in the middle
and lower thirds they lie in direct contact. In the middle and lower
thirds of the forearm the ulnar
nerve lies dorsal to the tendon of the flexor carpi ulnaris; at the
wrist it passes through a special
compartment in the anterior annular ligament to the radial side of the
pisiform bone to enter the
palm, where it divides into its terminal superficial and deep palmar
branches.
BRANCHES
The
only branches of the ulnar nerve given off in the arm are in the region
of the internal
humeral condyle, where several small twigs are distributed to the elbow
joint. About 2 cm.
below the medial condyle two branches are given off to the two heads of
the flexor carpi ulnaris;
at a slightly lower level another set of branches is given off to the
ulnar side of the flexor profundus digitorum. These motor branches
arise from the medial side of the dorsal quadrant of the
nerve; they pursue a relatively long intraneural course and may be
followed up the ulnar trunk
for some distance above the medial condyle by an intraneural
dissection. In the middle third of
the forearm the ulnar gives off a relatively insignificant palmar
cutaneous branch, which distributes branches to the ulnar artery and
follows the artery to the annular ligament, over which
it passes to supply a small area at the base of the hypothenar
eminence. At the junction of the
middle and lower third of the forearm there springs from the medial
side of the ulnar trunk a
large dorsal cutaneous branch, which at times nearly
approximates the ulnar trunk in size This
lorsal cutaneous branch, after passing under the tendon of the flexor
carpi ulnaris to the dorsal
aspect of the wrist, becomes cutaneous and supplies sensation to the
ulnar dorsal border of the
hand, and to the dorsum of the little finger as far as its terminal
phalanx and the ring finger to its
middle phalanx.
Terminal
palmar branches.-After passing under the annular ligament the ulnar
nerve
terminates in a superficial and deep branch. The superficial branch,
beyond giving a few twigs to
the palmaris brevis muscle, is strictly sensory and supplies sensation
to the ulnar side of the palm
and divides into an outer and inner digital branch, supplying sensation
to the little finger and
adjacent side of the ring finger. The deep branch is principally motor;
after its separation from
the ulnar trunk, it gives off branches to the muscles of the little
finger and enters its deep course
in the palm, accompanied by the ulnar
1030
artery, by passing
between the abductor and flexor brevis minimi digiti muscles,
penetrating the
opponens minimi digiti. It follows the course of the deep palmar areh
beneath the flexor tendons,
giving off branches to the dorsal and palmar interossei muscles and the
two inner lumbricales,
and terminates by sending motor branches to the adductor pollicis and
the inner head of the flexor brevis pollicis.
SURGERY
Lesions
of the ulnar nerve in the axilla are usually combined lesions of the
terminal
plexus type, and are dealt with as such.
In
the upper arm the ulnar nerve lies within the neurovascular bundle, and
any traumatism
sufficient to injure the ulnar will probably result in injury to the
median. As the ulnar nerve
leaves the axilla under the lower border of the pectoralis major, it
passes across the tendon of the
latissimus dorsi, in close relation to the musculospiral, and in this
region both occasionally
suffer simultaneous injury.
EXPOSURE IN THE ARM
Exposure
of the ulnar nerve in the upper part of the arm is obtained as with the
median,
through a long incision, paralleling the neurovascular bundle. This
incision differs, however, in
that at the junction of the middle and lower third of the arm it
diverges posteriorly, following the
internal intermuscular septum to the medial humeral condyle. The deep
fascia is now opened and
the medial border of the coracobrachialis above and the biceps below
retracted, exposing the
neurovascular bundle, which lies in the cleft between these muscles and
the long head of the
triceps. At the lower part of the axilla the neurovascular bundle is
covered by the pectoralis major
and, to obtain an axillary exposure, the pectoral tendon will require
division. The neurovascular
bundle is opened, exposing its contents and the ulnar nerve identified
above the lesion. About the junction of the middle and lower third of
the arm the lower segment of the ulnar nerve
is identified posterior to the internal intermuscular septum, after it
has left the neurovascular
bundle. Before disturbing the circumferential relationship of the nerve
by complete isolation, in
both upper and lower positions, the center of its lateral quadrant
should be carefully marked with accurately placed identification
sutures. The dissection of the nerve may now progress to the
point of lesion. If the identification sutures previously placed are
found to be some distance from
the lesion, as the dissection progresses they should be supplemented
with additional sutures,
carefully observing the surface markings of the nerve. Much difficult y
is experienced in the
dissection of the neurovascular bundle, particularly when it is invaded
with sear tissue, due to
bleeding from numerous venous and arterial radicals. This difficulty
may in a large measure be
obviated by isolation of the basilic and brachial veins below, and the
application of permanent or
temporary constriction. Arterial hemorrhage may be controlled by
isolating the brachial artery
above and applying a tape which may be adjusted to control its
circulation while branches are being ligated or accidental wounds in
the arterial wall repaired.
Defects
in the continuity of the ulnar trunk in the arm, if of a magnitude not
correctable
by primary nerve stretching, will call for transposition of the
1031
nerve from behind the
medial condvle of the humerus to a more ventral position, after which
advantage nmav be taken of elbow flexion-relaxation. When this
procedure fails to overcome the
defect, the ulnar nerve should be freely mobilized in the axilla and
recourse taken to the two-stage operation.
SURGERY IN TIIE REGION OF THE INTERNAL
HUMERAL CONDYLE
The
ulnar nerve, as it passes behind the internal humeral condyle is
exposed to frequent
trauma. Its involvement in war injuries is second only to lesions of
the musculospiral. Its lateral
surface, being in direct contact with the bone, and its medial surface
being very superficial,
renders it particularly susceptible to trauma.
PROGRESSIVE
PERIFERAL ULNAR PARALYSIS
Severe
injury to the ulnar nerve usually results in complete immediate
paralysis, while
frequently repeated slight trauma will result in a gradual progressive
type of peripheral paralysis,
in which sensation is slowly lost and atrophy of the intrinsic hand
muscles supervenes. The ulnar
nerve, because of its exposed position behind the medial huuneral
condyle, is commonly the
recipient of frequent mild degrees of trauma, though of suflicient
intensity to institute a gradual
compression paralysis, due to the production of intraneural scar
tissue. Occasionally this type of
ulnar paralysis will develop years after a trauma to the medial condvle
or the elbow joint. The
original trauma may escape memory, but is probably responsible for the
institution of some
anatomic change in the bone proximal to the nerve, or for a thickening
of the aponeurotic fascia
covering the nerve, producing compression or intensifying the effect of
ordinarv trauma to this
region.
In
lesions of this type, the ulnar nerve shouldl be transposed from its
exposed position
behind the humeral condyle to the less traumatized region anterior to
the condyle. This
procedure will usually suffice to correct most progressive peripheral
lesions, though when the
nerve is found to be indurated, its sheath should be opened and the
bundles subjected to internal
neurolysis. The nerve sheath is allowed to remain open for its
decompressive effect.
EXPOSURE
The
surgery of the ulnar nerve in the region of the internal condyle
necessitates exposure
in its lower humeral and upper forearm course. With the arm fully
abducted and in external
rotation, the forearm flexed and in extreme supination, a curved
incision is carried from the
junction of the middle and lower third of the arm, beginning along the
medial border of the
biceps, following the course of the nerve downward behind the internal
condvle to the forearm
where it follows its anterior ulnar border to the junction of its upper
and middle third. In the line
of this incision, the deep fascia is divided and the nerve identified
distal and proximal to the
lesion. In its lower humeral course. the nerve will be found, after
having penetrated the internal
intermuscular septum, following the posterior border of this structure,
lying upon the internal
head of the triceps or covered by its superficial fibers. It is
accompanied by the inferior profunda
artery which may usually be separated from the nerve
1032
to the internal condyle,
where ligation will be required, as in his region the artery and its
venae
comites anastomose freely with the ulnar recurrent artery and vein. The
preliminary ligation of
these vascular structures, both above and below the internal condyle,
where they lie in direct
contact with the nerve, will greatly enhance the dissection. The ulnar
collateral branch of the
musculospiral nerve, supplying the medial head of the triceps, follows
a course along the
posterior border of the internal intermuscular septum in close relation
to the ulnar nerve and care
should be used in avoiding its injury. At the internal medial condyle,
the ulnar nerve is protected
by a thick aponeurotic membrane stretching from the medial condyle to
the olecranon, as they are
occasionally adherent. Before the relationship of the nerve has been
disturbed in its bed, it should
be carefully marked by sheath identification sutures to prevent torsion
during subsequent suture.
The nerve, after being uncovered in its course posterior to the medial
condyle, will be found
entering the foramen bypassing under the tendinous arch, connecting the
two heads of the flexor
carpi ulnaris. The fibers of this arch are divided and the line of
cleavage between the two heads
of the muscle separated for a short distance, exposing the nerve in its
passage below this muscle,
where it lies upon the muscular fibers of the flexor profundus. In the
region of the condyle and
below, important branches will be found innervating the flexor carpi
ulnaris and the ulnar half of
the profundus digitorum; these motor branches spring from the medial
and posterior quadrant of
the nerve. The branches to the flexor carpi ulnaris leave the ulnar
trunk somewhat higher than
those to the profundus-usually about the level of the condyle. The
fibers innervating the flexor
carpi ulnaris may leave the nerve trunk as a single bundle,
subsequently dividing to supply its
two heads, or these branches may leave the parent trunk after their
division. If the ulnar sheath is
opened, however, they will be found united into a single branch or
bundle, and may be followed
some distance above the internal condyle. The lower branch, innervating
the ulnar half of the
flexor profundus digitorum, may likewise leave the nerve trunk as a
single branch, or after its
division. Within the nerve trunk, however, it may be followed as a
single bundle some distance
above the condyle, where it will be found to join with the bundle
containing the fibers to the
flexor carpi ulnaris. After these two bundles have combined, their
intraneural course may
frequently be followed as high as the middle third of the arm. The
intraneural dissection of these
branches is extremely important in transposing the nerve to a position
anterior to the humeral
condyle, in the correction of continuity defects-it is our only means
of preserving these branches
during such a procedure. Occasionally, in lesions in the region of the
medial condyle, these motor
branches may be found divided; and if they can not be identified and
repaired, provision should
be made for ulnar profundus paralysis by dividing the two medial
profundus tendons above the
wrist and uniting them with the two lateral profundus tendons which are
supplied by the median
nerve.
TRANSPOSITION OF THE ULNAR NERVE
Transposing
the ulnar nerve from its position behind the internal humeral condyle
to the
anterior surface of the elbow is a valuable procedure in over-
1033
coming defects in the
continuity of the nerve; it is also indicated in progressive peripheral
ulnar
paralysis in which the nerve is subjected to trauma when occupying its
normal position. In
overcoming defects, transposition of the ulnar nerve will shorten its
course and render it
susceptible to flexion-relaxation
FIG. 183 - Ulnar nerve,
showing scar tissue
as found at operation. Nerve exposed by splitting the two heads of
flexor carpi ulnaris; exposure of distal and proximal segments.
Identification sutures placed. A, Medial epicondyle; B. olecranon; C,
ulnar nerve, proximal segment; D, flexor carpi ulnaris, ulnar head; E,
ulnar nerve, distal segment; F flexor carpi ulnaris, humeral head; G,
internal intermuscular septum
FIG. 184.– Ulnar nerve
exposed above medial
humeral condyle preparatory for transportation anterior to the condyle.
Intraneural exposure and mobilization of branches to ulnar half of
flexor sublimis digitorum and flexor carpi ulnaris;
mobilization of branches should be carried at least 3 cms. Above
condyle. A, Medial epicondyle; B, flexor carpi
ulnaris, humeral head; C, ulnar nerve; D, wall of ulnar canal; E,
branch to flexor carpi ulnaris; F, branch to flexor
profundus digitorum; G, ulnar nerve, distal segment.
of the elbow, when
defects in the forearm of three or four inches may be readily overcome.
The
incision for ulnar transposition follows the course of the nerve from
the middle of the
arm to the middle of the forearm. The deep fascia is divided in the
line of the skin incision and
the nerve exposed throughout the length
1034
of this incision, care
being taken to place a sufficient number of identification sutures to
assure
alignment of the nerve, if suture is required. The anterior skin flap
containing the fat of the
superficial fascia is reflected, exposing the medial border of the
biceps and its tendon. The ulnar
nerve is now followed upward to the middle third of the arm where it
penetrates the internal
intermuscular septum; the septum is divided and the nerve made to pass
along its ventral border,
following the course of the neurovascular bundle to the ante-cubital
fossa. To transpose the nerve
below the medial condyle so that it will follow a straight line down
the arm and forearm, its
motor branches to the flexor carpi ulnaris and the profundus digitorum
must be mobilized some
distance up the nerve trunk to prevent stretching and tearing in
transposing the nerve. The nerve
in its transposed position passes over those muscles arising from the
medial condyle. If the
cutaneous structures in this region have been well preserved and
contain sufficient subcutaneous
fat, the writer
FIG. 185.- Ulnar nerve
transposed; defect
overcome by transposition and flexion-relaxation of elbow; branches
preserved through mobilization
prefers transplanting
the nerve in this superficial position, where it is covered merely by
the fat of
the superficial fascia. Some operators, however, prefer directing the
nerve through a muscular
tunnel below the common heads of origin of the superficial muscles
springing from the medial
condyle, the bed of the nerve being the flexor profundus digitorum.
This may be accomplished in
two ways, depending upon the ability to preserve the motor branches to
the flexor carpi ulnaris
and profundus digitorum. If the motor branches have been sacrificed,
the nerve is passed through
a tunnel between the sublimis and profundus digitorum, made by passing
forceps between these
muscles, widening the tunnel and drawing the free end of the nerve
through. The second method
consists in dividing the superficial muscles close to their origin to
the medial condyle, placing the
nerve in the cleft and resuturing the muscles above it. This has the
disadvantage of possibly
interfering with the nerve supply of normal muscles, and also of
inflicting additional trauma to
the
1035
structures surrounding
the nerve. While the tunneling procedure is less apt to injure the
nerve
supply of adjacent muscles, it undoubtedly invites an excess of sear
tissue by virtue of the trauma
inflicted.
EXPOSURE IN THE
MIDDLE AND LOWER THIRDS OF THE FOREARM
An
incision extending from the radial side of the pisiform bone toward the
medial
condyle will follow the course of the ulnar nerve in the forearm. After
the deep fascia has been
divided, the tendon of the flexor carpi ulnaris is identified. It will
be remembered that the lateral
or radial border of the flexor carpi ulnaris is tendinous for some
distance up the forearm, while
from its medial or ulnar border muscular fibers radiate almost as far
down as the wrist joint.. The
ulnar nerve, accompanied by the ulnar artery and its venae comites.
lies beneath the radial border
of the flexor carpi ulnaris tendon and to the ulnar side of the flexor
sublimis digitorum.
Following upward the cleft between these muscles, the ulnar nerve will
be found resting upon the
flexor profundus digitorum and covered by its thin sheath. It is
advisable to first identifv the
nerve in the region of the wrist, after which it may be followed upward
by separating the loose
attachment between the flexor carpi ulnaris and the flexor sublimis
digitorum: the identification
of the line of cleavage between these muscles is facilitated by
following up the radial tendinuos edge of the
flexor carpi ulnaris. If dificulty is encountered in exposing the
proximal end of
the nerve, it may be readily identified at the medial condyle, which it
leaves to pass between the
two heads of the flexor carpi ulnaris. These two heads may be separated
for some distance and
the nerve followed as it passes below the belly of the humeral head,
which latter may the
conveniently elevated by tape retraction, its radial border having been
previously separated from
the sublimis and palmaris longus. In the upper part of the middle third
of the forearm, the ulnar
artery joins the nerve and follows it throughout the remainder of its
course. In the middle third of
the forearm a small palmar cutaneous branch is given off, which follows
the ulnar artery down
the forearm and passes over the annular ligament: this branch is
unimportant and may be
sacrificed with impunity. About the lower third of the forearm, though
at times much higher, a
large dorsal cutaneous branch arises from the medial side of the ulnar
trunk and passes under the
tendon of the flexor carpi ulnaris to supply the integument of the
ulnar dorsal side of the hand
and fingers. This branch is occasionally of rather large size and must
not be confused with the
main ulnar trunk. It follows a relatively long intraneural course and
its preservation is important,
as it supplies sensation to the much traumatized ulnar border of the
hand and little finger.
Lesions
of the ulnar nerve in the lower two-thirds of the forearm are commonly
associated with more or less tendon injury, whieb should be repaired
before the nerve is sutured.
If sublimis or profundus tendons on the ulnar side are injured, they
should be freed of all sear
tissue and reunited if possible. If suture of the divided tendons is
not possible, they should be
anastomosed to intact sublimis or profundus tendons, and their bellies
above freed of scar and
likewise united. Occasionally the palmaris longus may be transplanted
into the distal end of the
divided sublimis tendons.
1036
SURGERY OF TIHE ULNAR NERVE IN THE PALM
The
ulnar nerve enters the palm by passing through the annular ligament in
a
compartment of its own along the radial border of the pisiform bone,
and in the palm divides into
its two terminal branches-a superficial branch, mainly sensory, and a
deep branch, principally
motor to the ulnar intrinsic hand muscles. These terminal ulnar
branches do not lend themselves
favorably to surgical repair, though as with the median, occasional
instances will be found where extremely localized injuries involving
the nerve with small defects will permit repair.
EXPOSURE
Exposure
is made through an incision extending from the radial border of the
pisiform
bone to the interspace between the fourth and fifth fingers. The nerve
is localized at the wrist and followed into the hand by dividing the
annular ligament, the palmar fascia and
the palmaris brevis, exposing the flexor brevis minimi digiti and the
opponens of the little finger.
By retracting the ulnar border of the incision, the deep branch may be
followed and exposed as it
passes in a cleft between the flexor brevis and abductor, which muscles
require careful
identification as they are important landmarks. If the interspace
between these muscles is spread, exposing the opponens, the
FIG. 186.- Branches of ulnar
nerve in hand. A,
Digital cutaneous branch, fourth and fifth fingers; B, digital branch,
fifth finger; C, palmaris brevis; D, motor branch to intrinsic muscles;
E, ulnar nerve; F, ulnar artery; G, palmar
fascia; H, palmaris longus tendon; I, annular ligament
nerve may be followed to
a point where it penetrates the latter muscle. After penetrating the
opponens, the deep palmar branch passes below the flexor tendons and in
this region is
practically inaccessible. The superficial palmar branch may be
identified by its superficial
position and by the distribution of its digital branches. Occasionally
it is possible to effect
individual suture of these digital branches, their arrangement being
similar to the median digital
branches.
In
attempting repair of the small cutaneous or motor branches of the
median or ulnar
nerve in the hand, the operator should proceed with extreme care and a
full appreciation of the
difficulties involved, in that the disability resulting from the
inflicted surgical trauma may be
greater and overshadow the original disability.
1037
DEFECTS IN
CONTINUITY
Because
of the passage of the ulnar nerve posterior to the internal humeral
condyle, it
does not lend itself to flexion-relaxation of the elbow joint. In fact,
flexion of the elbow joint
tends to stretch the nerve, which normally is relaxed by forearm
extension. It therefore becomes
necessary in most ulnar defects to resort to transposition of the nerve
from its posterior position
behind the internal condyle to an anterior position, by which the
operator utilizes the elongating
effect of directing the nerve from an angular to a straight course, and
which also permits an
extensive relaxation of the nerve during forearm flexion.
Defects
in the forearm up to 3 or 4 inches may be overcome by utilizing
transposition of
the ulnar nerve with flexion-relaxation of the elbow. Defects of
greater magnitude in the forearm
require extensive mobilization of the nerve, which should be continued
to the wrist below and to
the upper third of the arm above, when another inch may be added by
ulnar flexion of the wrist
and abduction of the arm. If the surgeon, having availed himself of
these procedures, finds
difficulty in obtaining end-to-end approximation, he must then resort
to the two-stage operation,
described under general technique. An endeavor should always be made to
preserve the motor
branches at the elbow, though they may be sacrificed if their extensive
intraneural mobilization
fails to give sufficient relaxation to the nerve. If it becomes
necessary to sacrifice the motor
branches to the flexor carpi ulnaris and ulnar half of the profundus
digitoruin, the function of the
profundus tendons may be maintained by transplanting them at the wrist
into the two remaining
active profundus tendons.
The
surgeon is rarely justified in sacrificing the dorsal cutaneous branch
of the ulnar for
relaxation purposes. If it is found to interfere with ulnar
mobilization, it should be freed as far as
possible along the ulnar border of the forearm. Sacrifice of the dorsal
cutaneous branch involves
a permanent anesthesia of the ulnar border of the hand and little
finger, which may in itself
necessitate amputation of these parts, because of the constant
irritation of trophic or traumatic
sores.
In
the arm, large defects of the ulnar nerve necessitate exposure well up
into the axilla
and well down into the forearm. Flexion-relaxation is inhibited in
upper defects of the nerve by
the motor branches at the elbow, and to obtain its full effect,
sacrifice of these branches is usually
necessary. In transposing the ulnar nerve for the correction of
defects, the surgeon should assure
himself that the nerve is freely mobilized in the region of the
internal intermuscular septum.
Ulnar defects, which can not be overcome by stretching, transposition,
and flexion-relaxation of
the elbow, wrist, and shoulder are probably beyond repair, though in
such cases the surgeon
should not neglect the possibilities of a successful graft, but
grafting may be used only as a
procedure of last resort.
SECONDARY SUTURES
Surgery
of the ulnar nerve gives perhaps more unsatisfactory results than any
other nerve,
primarily because of failure in regeneration of the ulnar intrinsic
hand muscles. In the writer's
experience, regeneration of the inter-
1038
ossei muscles is absent,
after four years, in 94 per cent of ulnar sutures. These delicate,
highly
specialized intrinsic hand muscles reach an extreme degree of muscle
degeneration in a
comparatively short period. In several cases of ulnar paralysis,
resulting from compression
lesions, in which there has been a satisfactory restoration of ulnar
sensation following neurolysis,
the ulnar intrinsic hand muscles have remained paralyzed where the
uncorrected lesion had
existed beyond one year. The writer has observed a number of cases in
which some function had
returned in the muscles of the hypothenar eminence and the adductor
pollicis, though no action
could be demonstrated in the interossei.
The
restoration of function in the ulnar portion of the profundus digitorum
and the flexor
carpi ulnaris occurs in approximately 60 percent of cases, following
suture. In most cases of
ulnar suture in which there has been some degree of axis cylinder
regeneration, some return of
sensation is found in the ulnar border of the hand and little finger.
This sensation, in most
instances, after a period of two years is nondiscriminative in
character, all types of sensation
being described as tingling. Usually after the third year, the power to
discriminate between
various sensations gradually returns to a greater or lesser degree, but
usually sufficient to afford
protection to this region of the hand.
In
view of these facts, a failure of interossei regeneration should not be
considered as
defective regeneration beyond our usual experience, and this defect
does not call for secondary
surgical intervention. The failure of sensory restoration in the ulnar
region is indicative of
defective regeneration and does not call for intervention. In
considering defective regeneration in
the ulnar nerve, sensation deserves the greatest attention. Any hope of
regeneration, to a
satisfactory degree, in the intrinsic hand muscles may be practically
abandoned for an
uncorrected paralysis of one year's standing. Paralysis of the flexor
carpi ulnaris and ulnar half of
the profundus digitorum is productive of no great disability and the
slight disability existing from
their paralysis may readily be overcome by tendon transplantation.
DETERMINATION OF REGENERATION
The
examiner must depend entirely upon Tinel's sign for information during
the early
stages of ulnar regeneration following suture. After six months, if
formication is not elicited in
the distal segment of the nerve. it should be considered as defective
neuraxon regeneration, and
secondary surgical intervention is indicated.
Certain
precautions must be taken in the presence of much scar tissue in the
region of the
suture, in eliciting this reaction. The tugging of a scar upon a
neuroma or suture line may elicit
the reaction of formication in a region below the regenerated nerve
fibers. When Tinel's sign is
elicited throughout the distal nerve trunk and this reaction is
intense, it may be prognosticated
that sensory fibers are regenerating satisfactorily, and the patient
assured of so men degree of
sensory restoration. A persistent loss of sensation in the ulnar region
with a sensitive suture line,
giving evidence on palpation of neuroma formation, suggests defective
suture and secondary
exposure is indicated.
1039
The
writer has observed scveral instances in which there was no evidence of
regeneration
following a neurolysis of the ulnar nerve. Such failures, frequently
commented upon by other
writers, need not, necessarily, call for resection of the nerve and
suture, unless an internal
neurolysis has demonstrated a complete blocking of the scarred trunk,
with obliteration of motor
bundles. These defective end results, following neurolysis, are usually
due to imperfect surgical
judgment at the time of operation, when an external neurolysis was
probably the extent of the
operation; the real compressive factors evidently were overlooked.
In
complete persisting failure of regeneration, and in irreparable
defects, where the
anesthetic area is constantly being subjected to trauma, and suffering
trophic disturbances,
amputation of the little finger offers the only solution. Occasionally
this amputation must also
include the ulnar metacarpal region. A very deforming fibrous griffe
may be allowed to develop
in the little finger, greatly diminishing the usefulness of the hand,
which also may justify
amputation.
COMBINED LESIONS
OF MEDIAN AND ULNAR NERVES
The
close anatomic relationship existing between the median and ulnar
nerves in the
middle and upper thirds of the arm makes their combined
lesions|comparatively frequent. Less
often are combined lesions of these nerves experienced below the lower
third of the arm, where
they pursue a divergent course, though combined lesions are by no means
uncommon in
extensive gunshot injuries of the forearm. The importance of combined
median and ulnar lesions
is emphasized by the seriousness of the resulting diasbility, in which
all of the extrinsic and
intrinsic flexion power of the fingers is lost, as well as the power of
pronation; this paralysis,
combined with complete anesthesia of the palm and fingers, renders the
extremity practically
useless.
The
surgical repair of combined median and ulnar lesions differs in no
respect from the
individual repair of these nerves, each of which should be treated
surgically as an individual unit.
The necessity for a separate consideration of combined median and ulnar
lesions is advisable,
however, because of supplementary surgical procedures indicated in a
total absence of or
defective nerve and muscle regeneration.
In
the great majority of instances following a successful end-to-end
approximation in both
median and ulnar nerves (if due respect has been given, the prevention
of torsion during suture)
there will be a restoration of voluntary motor power in the pronators,
wrist flexors, and extrinsic
digital flexors, with a gradual return of sensation; the total
anesthesia of the fingers is replaced at
first by a nondiscriminative type of anesthesia, which later, after two
or three years, is slowly
supplemented with the power of tactile localization and discrimination.
This degree of functional
restoration following the suture of these nerves is probably as
complete as may reasonably be
expected. The residual disability is confined to a loss of function in
the intrinsic hand muscles,
expressed by: (1) Loss of opponens function of the thumb; (2) inability
to flex the
metacarpophalangeal joints; (3) loss of extension of the
interphalangeal joints with
hyperextension of the metacarpophalangeal joints.
1040
These
disabilities produce a deformity commonly characterized as the "claw
hand" of
complete intrinsic hand-muscle paralysis. The long flexors of the
fingers are unable to conjointly
flex the metacarpophalangeal joints and terminal phalanges; attempts at
flexion are followed by a
rolling up of the terminal phalanges, in which the nails, instead of
the palmar surface of the
fingers meet, the palm, due to the fact that flexion of the
metacarpophalangeal joints does not
occur synchronously with phalanx flexion, and when flexion does occur
at the
metacarpophalangeal joints it is only after the interphalangeal joints
are completely flexed.
The
thumb disability consists in the loss of opponens action, and though
flexion of the
distal phalanx is restored through the long flexor of the thumb, this
member rests against the
radial border of the hand, and normal thumb and index finger opposition
("pinch action") is
replaced by a very defective and ineffectual approximation, in which
the nail of the thumb meets
the radial side of the index finger, objects being held between the
thumb nail and this finger very
much as a small boy holds a marble for shooting.
The
extensor communis digitorum is capable of extending the terminal
phalanges when
the long flexors are completely paralyzed, but it seems to lack this
power when they are active.
Its principal action is extension at the metacarpophalangeal joints. In
intrinsic hand-muscle
paralysis the fingers can not be completely extended; during attempts
at extension the terminal
phalanges remain partially flexed, while the metacarpophalangeal joints
are hyperextended. The
interossei, by virtue of their insertion into the extensor tendons
beyond the metacarpophalangeal
joints, accomplish terminal phalangeal extension; in this they are
assisted by the lumbricales,
which also by virtue of their origin from the tendons of the profundus
digitorum and their
insertion with the interossei into the extensor tendons, near the
center of the first phalanx,
prevent hyperextension of the metacarpophalangeal joints, as the
lumbricales are flexors of these
joints and antagonists to the extensor communis digitorum. The
function, therefore, which we
wish to restore in intrinsic hand-muscle paralysis is the opposing
action of the thumb, and flexion
of the metacarpophalangeal joints, with extension of the terminal
phalanges,
metacarpophalangeal flexion is particularly important in the index
finger.
For
the restoration of opponens function, or rather the maintenance of the
thumb in the
opponens position, Major Baldwin attempted arthrodesis of the first
metacarpophalangeal joint
and fixed it in an opposed position at an angle of 60 degrees, which is
practically the normal
angle existing between the first and second metacarpals during pinching
action. This operation,
though restoring the opponens position of the thumb and greatly
improving its function. has a
distinct disadvantage; it does not permit abduction and extension, the
thumb remaining
continuously opposed over the palm, in which position it is like the
drop thumb of extensor
paralysis and is frequently in the way.
The
writer devised and practiced a tendon transplant for the restoration of
opponens
function in the thumb, which duplicates this action perfectly, at the
same time allowing its
complete extension. The procedure consists in directing the short
extensor tendon of the thumb
through a tunnel under the fat of the
1041
superficial fascia; from
the palm it is directed under the annular ligament to the wrist where
it is
anastomosed to the palmaris longus. The end results of this procedure
have been observed in a
series of cases for a period of more than three years. In each instance
the opposing action of the
thumb has remained excellent and has gradually increased in power with
the development of the palinaris longus muscle.
TENDON TRANSPLANTATION FOR RESTORING OPPONENS
ACTION TO THE THUMB IN INTRINSIC
HAND-MUSCLE PARALYSIS
This procedure is conducted entirely under local
anesthesia,
which assists materially in
hemostasis; it also permits the testing out of the transplant during
operation, by voluntary
contraction of the palmaris longus, the patient having been previously
instructed in the
contraction of this muscle.
TECHNIQUE
a.
A midventral wrist incision is made over the course of the palmaris
longus tendon,
extending from the base of the palm just below the annular ligament,
upward for a distance of
about 7 cm. The palmaris longus tendon is identified and freed, and its
attachment to the palmar
fascia divided, after it has passed over the annular ligament. The
median nerve lies immediately
below the palmaris tendon and is usually exposed with the retraction of
this tendon. A pair of
blunt-curved forceps is now passed under the annular ligament at this
point, and made to emerge
below its palmar border, by penetrating the palmar fascia, the forceps
being spread to enlarge the opening. The opening in the palmar fascia
is enlarged sufficiently, by excising its edges, to
prevent subsequent constriction of the transposed extensor tendon,
which is passed through this
opening.
b.
dorsal thumb incision from the base of the proximal phalanx extends to
the radiocarpal
articulation, bisecting the "anatomical snuffbox." To the palmar side
of this incision the short
extensor tendon is located as it lies in a separate sheath in
juxtaposition with the dorsal border of
the tendon of the extensor ossis metacarpi pollicis. The long extensor
tendon, which lies to the dorsal side of the incision, must not be
confused with the short extensor tendon-traction on the
tendon of the long extensor produces extension of the distal phalanx.
The sheath of the short
flexor is opened and the tendon followed downward to the
metacarpophalangeal joint of the
thumb. This short flexor tendon is divided about 10 cm. above its
insertion, where it lies in close ipproximation with the tendon of the
extensor ossis.
c.
A tunnel is now maed between the lower ends of the two incisions,
undermining the fat
of the superficial fascia in a line connecting the annular ligament and
the metacarpophalangeal
joint of the thumb. Through this tunnel a pair of forceps is passed
from the ventral to the dorsal
incision and the divided end of the extensor brevis pollicis tendon
caught and drawn through the
tunnel to the opening in the palmar fascia. Its end is then grasped by
the previously placed
subannular forceps, drawn through the opening in the
1042
palmar fascia under the
annular ligament to the wrist. where it is anastomosed to the palmaris
longus tendon, with sufficient tension to produce marked abduction and
opposing rotation of the
thumb. When the palmaris longus is absent, as it is in approximately 20
per cent of cases, the
transposed extensor tendon may be passed through a slit in the flexor
carpi radialis tendon
FIG. 187.- Tendon transplant
for restoring
opponens position and function to the thumb in intrinsic hand muscle
paralysis; exposure of palmaris longus tendon
FIG. 188.- Tendon transplant
for restoring
opponent position and function to the thumb in intricate hand muscle
paralysis. Tendon of palmaris longus divided; opening made in palmar
fascia at upper part of annular ligament.
and sutured, without
division of the tendon of the latter muscle. (In the writer's
experience, more
satisfactory end results have followed transplantation into the
palmaris longus.) The thumb now
lies across the palm in an opposed and abducted position and with the
wrist slightly flexed: the
skin incisions are closed, and the hand dressed with the thumb and
fingers grasping an unrolled
1043
bandage, which tends to
maintain the thumb in the desired position. The fist, with the wrist
flexed, is firmly supported with suitable bandages or splinting to
insure the maintenance of this
position.
The
subsequent treatment is conducted along lines common to the
after-treatment of all tendon transplantations. Reeducation is, as a
rule, not
FIG. l89.- Tendon transplant
for restoring
opponens position and function to the thumb in intrinsic hand muscle paralysis; exposure
of
short extensor of the thumb
FIG. 190.- Tendon transplant
for restoring
opponens position and function to the thumb intrinsic hand muscle
paralysis. Passage of the divided short extensor tendon through a
subcutaneous tunnel in the thenar eminence and
through opening in palmar fascia, where it passes below the annular
ligament and is anastomosed to the palmaris
longus tendon, holding the thumb in the opponens position
difficult, and a few
demonstrations will usually be found sufficient to institute effective
opponens
action of the thumb in individuals of ordinary intelligence. This
transplant is synergetic, in that
forceful prehension of the thumb is accompanied normally by contraction
of the palmaris longus.
1044
TENDON TRANSPLANTATION FOR RESTORING
METACARPOPHALANGEAL FLEXION AND
EXTENSION OF THE TERMINAL PHALANGES (LUMBRICALES AND INTEROSSEI
FUNCTION)
For
the restoration of inetacarpoplhalangeal flexion, Stiles devised an
ingenious operation
in which he alters the insertion of the flexor sublimis digitorum
tendons, rendering them flexors
of the metacarpophalangeal joints by suturing them to the exterior
communis tendons distal to
the knuckle, which makes them also extensors of the interphalangeal
joints, thus causing the flexor sublimis digitorum to subserve the
function of both interossei and lumbricales. This
procedure may be carried out on each finger or it may be limited to the
index.
TECHNIQUE
a.
Through a mid-dorsal incision, the skin and fascia are divided, and the
common
extensor exposed. The insertions of the interossei and lumbricales into
its lateral aspect are
identified and freed.
b.
An incision is made along the flexor aspect of the digit from the
transverse palmar
crease to the distal interphalangeal joint, exposing the flexor sheath,
which must not be opened
through the line of incision. About the base of the metacarpophalangeal
joint, the sublimis
tendon divides to permit the passage of the profundus tendon. The
lateral and medial slips of the
tendon then pass forward to be attached into the sides of the middle
phalanx. Near their
insertion a small incision is made through the sheath of each tendon
slip anl the tendon divided.
Next the tendon is identified opposite the metacarpophalangeal joint,
where it has just begun to
split; an opening is made in the sheath at this point, and each tendon
slip pulled out of its sheath.
Stiles emphasizes the importance, in making these openings in the
sheath, of not disturbing the
small bands which hold the profundus tendon in place opposite each
phalanx, "otherwise the
tendon will stand forward under the skin like a bowstring when the
patient attempts to flex the
finger, and will lose its pull on the terminal phalanx." Each half of
the sublimis tendon is now
passed through a subcutaneous tunnel on each side of the digit to the
dorsal incision and threaded through an opening made in the expanded
portion of the extensor sheath which receives
the insertion of the interossei and lumbricales. The two tendons are
sutured in this position with
linen, with the knuckle flexed at right angles and the interphalangeal
joints straight. Any excess
of tendon is clit away alud the raw ends buried by a suture through the
two sides of the coinniunis. Both wounds are closed and the fingers
fixed by pads and bandages in a position of
metacarpophalangeal flexion and terminal phalanx extension.
IRREPARABLE DEFECTS OF THE MEDIAN AND ULNAR
NERVES
An
irreparable defect of the median and ulnar nerves is attended with such
a degree of
disability to the extremity that it may be considered as permanently
useless, unless some flexion
function can be restored to the fingers through tendon transplantation.
The accompanying
anesthesia, however, seriously diminishes the functional usefulness of
the hand, even though
digital flexion is regained through tendon transplantation. Before
resignation is
1045
FIG. 191.- Diagrammatic
explanation of viable
neuroplastic transplant for filling of median defect in irreparable
lesion of both median and ulnar nerves. A Showing large irreparable
defect of both median and ulnuir nerves: the upper segments of both
nerves are marked with identification sutures.
B, Proximal end of both nerves united by end-to-end suture. Ulnar nerve
divided to permit degeneration of fibers, the central end of which is
injected with alcohol
to prevent regeneration of ulnar fibers in that portion of ulnar trunk
which is to be used later as a viable transplant. C, Second stage of
operation,
showing transplant which now contains regenerated median fibers turned
down and approximated to the end of the distal segment of the median,
overcoming the defect, the ulnar nerve being
sacrificed to repair the median
1046
made to an irreparable
median and ulnar defect (the two-stage operation for nerve repair and
grafts having failed), the surgeon should consider the possibility of
preserving some type of
sensation in the fingers by nerve anastomosis. Harris suggested
anastomosing the radial nerve to
the distal stump of the median. This procedure may be followed by some
restoration of sensation
in the median sensory area of the hand and fingers; this sensation,
however, is attended with
dorsal localization, and although it protects the fingers by replacing
anesthesia with a defectively
localized sensibility, it contributes little to functional usefulness.
SACRIFICE OF THE ULNAR NERVE AS A VIABLE
NEUROPLASTIC TRANSPLANT FOR THE REPAIR OF
A MEDIAN DEFECT
When
all hope has been definitely abandoned of effecting approximation in
both median
and ulnar nerves, the disability may be diminished by using the ulnar
nerve as a viable
neuroplastic transplant for bridging the defect in the median, in the
hope of restoring at least
median sensation, and possibly function, in the extrinsic muscles of
the hand. If this motor
restoration is possible, opponens function and metacarpophalangeal
flexion may be restored by
tendon transplantation, and a very useful hand provided; if it is found
impossible to restore motor
function, flexion of the digits may be restored to some degree by
tendon transplantation and some
usefulness, at least, regained.
TECHNIQUE
First
stage.-The proximal ends of both median and ulnar nerves are
exposed,
the scar
tissue and neuroma resected, after which they are carefully
approximated, following the usual
technique of end-to-end suture, extreme care being taken to prevent
torsion of the nerve trunks in
this approximation. This procedure results in the formation, after
anastomosis, of a loop uniting
the proximal ends of these nerves. Without disturbing the bed of the
ulnar nerve any more than
necessary, it is exposed some distance above the anastomosis and
divided to permit Wallerian
degeneration of the nerve fibers in that portion of the ulnar trunk
which at the second operation
will be turned down to meet the distal end of the median as a
transplant. This transplant should
be slightly longer than the defect--if the defect be 5 inches, the
ulnar
nerve should be divided 5½ or 6 inches above its anastomosis to the
median. The upper end of
the divided ulnar trunk is
injected with alcohol or treated after the manner of amputation
neuromas, to prevent
regeneration of ulnar fibers down the transplant. It is essential in
this procedure to conserve in
every way the nutrition of that portion of the ulnar trunk which is
being used as a transplant;
hence the necessity of not disturbing its bed. The median fibers, in
regenerating, will now pass
around the loop and follow the transplant upward, and if sufficient
time be allowed they will
form a neuroma at the upper end of the transplant where the ulnar nerve
was divided. Inasmuch
as regeneration occurs, approximately, at the rate of 1 inch per month,
the second operation
should be postponed until the median fibers have completely traversed
the transplant; in a 5-inch
transplant the second operation should be planned at the end of the
sixth month, allowing a
month of grace.
1047
Second
stage.- Both proximal and distal segments of the median nerve are
now exposed; in
the lower segment the center of the ventral quadrant is marked by
identification sutures before
disturbing its relations; in the upper segment the loop of anastomosis
between the median nerve
and the transplant is now carefully exposed and the transplant followed
upward to its end, where identification sutures are placed in the
center of its exposed ventral quadrant. The transplant is
freed by careful dissection and turned down to meet the end of the
distal segment of the median;
the scar tissue is now resected from both ends of the nerve and
approximation effected, with
strict care toward the prevention of torsion. The selection of a
satisfactory bed for the transplant is important.
In
the above procedure the defect in the median nerve is filled by a
viable transplant
through which median fibers have regenerated and is far more likely to
prove successful than
nonviable grafts.
When
the ulnar nerve has been sacrificed and the ulnar portion of the hand
and little
finger is the subject of traumatic and trophic sores amputation is
indicated. If, however, the skin
of the ulnar portion of the hand remains in good condition through
proper protection, restoration
of sensation can be obtained in certain instances by anastomosing the
radial nerve to the ulnar.
TENDON TRANSPLANTATION FOR COMPLETE FLEXOR
PARALYSIS
If
passive movements of the wrist and fingers are unrestricted, tendon
transplantation may
be utilized to restore, to some extent, digital flexion; though flexion
may be restored to a certain
degree through transplantation of extensors, the loss of the intrinsic
hand muscles greatly limits
the usefulness of the hand beyond the ability to hold or carry objects.
TECHNIQUE
a.
Splitting the tendon of the extensor carpi radialis longior, one slip
of which is
transplanted into the sublimis and profundus tendons of the index
finger, a second slip is
transplanted into the same tendons of the ring finger-through a long
incision, extending from the
base of the thumb to the upper third of the dorsum of the forearm, the
long ribbonlike tendon of
the extensor carpi radialis longior is identified between the extensor
brevis, to its ulnar side; and
the brachioradialis, to the radial side. At the wrist, these tendons
are crossed by the bellies of the
extensor ossis metacarpi pollicis, extensor brevis pohlicis, and the
tendon of the long flexor of
the thumb. The tendon of the long radial extensor is divided at its
insertion into the second
metacarpus. Its sheath is opened high up and the tendon withdrawn and
split. The tendon of the
brachioradialis is now an identified and divided, and its borders freed
from fascial attachments some distance up the forearm; in mobilizing
the brachioradialis caution should be used in the
isolation of the radial nerve and artery, which lie on its under
surface. Several muscular branches
of the radial artery will require ligation.
b.
Transplantation of the brachioradialis tendon into both flexor tendons
of the ring and
little fingers--a ventral incision is now made, extending from the base
of the thumb, near the
insertion of the flexor carpi radialis tendon, along the radial border
of the flexor surface of the
forearm to the junction of its upper
1048
and middle thirds. The
skin and fat of the superficial fascia is undermined between the two
incisions, permitting the passage of the extensor and brachioradialis
tendons to the ventral aspect
of the forearm in a straight couse. Medial retraction of the ventral
incision permits exposure of
the long flexor tendons, each of which should be identified and
arranged in pairs, sublimis and
profundus for each finger. T
The
long flexor of the thumb is identified and separately isolated. With
the fingers
completely flexed, the lateral slip of the divided long extensor tendon
is passed through a slit in
the sublimis and profundus flexors of the index finger; the medial half
of the radial extensor
tendon is anatomosed into both flexor tendons of the ring finger. The
tendon of the brachioradial
is is now brought forward in as direct a line as possible and inserted
in alike manner into the
flexor tendons of the ring and little fingers.
c.
Transplanting extensor ossis metacarpi pollicis into the flexor lungus
pollicis---the
extensor ossis metacarpi pollicis tendon is divided at its insertion
and transplanted into the long
flexor of the thumb, with the thumb flexed over the previously flexed
fingers, making a fist.
After the proper tension has been placed on these transplanted tendons,
so that the fingers are
flexed equally, and with the wrist in partial flexion, the tendons are
anchored.
Both
dorsal and ventral skin incisions are now closed while the hand is
maintained in
complete digital and partial wrist flexion. This position is maintained
by suitable pads and
bandages, after a small unrolled bandage placed in the hand.
(After-treatment and reeducation
are conducted along the usual lines.)
THE
SCIATIC
TRUNK AND ITS TERMINAL DIVISIONS
GENERAL ANATOMY
The
sciatic trunk is formed by the ventral and dorsal divisions of the
fourth and fifth
lumbar, and second and third sacral nerves. The ventral divisions go to
make up the medial or
tibial portion of the sciatic trunk, while the dorsal form its lateral
or peroneal portion.
The
tibial and peroneal portions of the sciatic trunk are from a
physiologic standpoint
totally differentiated, though anatomically they are usually
incorporated into a single nerve trunk
for some distance down the thigh. The extent of their union, however,
varies, and occasionally
the sciatic trunk is replaced by two distinct nerves, emerging from the
great sacrosciatic foramen.
More often however, their union continues to the upper part of the
popliteal space, where the
sciatic trunk divides into its terminal divisions; the medial or tibial
portia becoming the internal
popliteal nerve, while its lateral or peroneal forms the external
popliteal nerve. The separation in
the thigh of the component tibial and peroneal portions of the sciatic
trunk is always more or less
evident, varying from a complete separation, in which each nerve has a
distinct and separate
sheath, to the type in which inspection alone fails to demonstrate the
anatomical division and in
which palpation is required to give the surgeon a clue as to the line
of cleavage. These nerves,
when combined in a single sheath, are anatomically separated by a
septal prolongation of the
sheath, which is usually evident on cross section. As the trunk
proceeds down the thigh, the
demarcation between its component parts becomes more conspicuous on its
surface, and it
dividing septal sheath shows greater development.
1049
Though
the tihial portion of the sciatic trunk is usually described as lying
medial, and the
peroneal portion lateral, the line of division does not strictly follow
a ventrodorsal plane; the
tibial portion lies somewhat more ventral than dorsal, while the
peroneal portion occupies a
dorsolateral position.
After
emerging from the pelvis to the dorsum of the thigh, through the great
sacrosciatic
foramen under the pyriformis muscle, the sciatic trunk passes down the
posterior aspect of the
thigh to the popliteal space. In its upper part it lies on the external
rotators of the thigh, and
below these upon the dorsal surface of the adductor magnus. In its
gluteal portion, the nerve is
covered by the gluteus maximus; in the thigh it runs parallel with and
to the lateral side of the
flattened tendon of the semimembranosus, and is crossed and covered in
most of this portion by
the thick belly of the ischial head of the biceps.
NERVE TO HAMSTRING MUSCLES
The
nerve to the hamstring muscles, while commonly incorporated within the
sheath of
the tibial portion of the sciatic trunk, should not be regarded as a
collateral branch of the tibial
nerve, but rather as one of the three separate elements, which, being
bound together by a common
sheath, constitute the great sciatic trunk, namely, from within
outward, nerve to the hamstrings,
tibial nerve, and peroneal nerve. The nerve to the hamstrings may or
may not be incorporated
within the sheath of the sciatic trunk, but always lies to the medial
side of the tibial portion of the
sciatic; when incorporated within its sheath it is usually anatomically
separated by a well-developed sheath of its own and may be readily
separated from the sciatic trunk. The short or
humeral head of the biceps, however, is supplied about, the middle of
the thigh a branch which
leaves the lateral surface of the peroneal portion of the sciatic. This
branch has a distinct
intraneural course and may or may not he regarded as a collateral
branch of the peroneal nerve.
The nerve to the hamstrings. applies the semitendinosus,
semimembranosus, long head of the
biceps, and a portion of the adductor magnus.
TERMINAL BRANCHES
The tibial nerve (internal
popliteal), which formerly occupied a
ventro-medial position,
upon leaving the sciatic trunk in the lower third of the thigh. Enters
the popliteal space, where it
lies in a pad of fat, superficial to the popliteal vessels. It passes
longitudinally through the middle
of the popliteal space, from which it emerges by passing ventral to the
union of the two heads of
the gastrocnemius. It terminates at the lower border of the popliteus
muscle, by passing through
an arch in the soleus muscle, accompanied by the popliteal artery and
vein, where it becomes the
posterior tibial nerve.
In
the popliteal space, motor branches arise to supply the gastrocnemius.
plantaris, soleus,
and popliteus muscles: these branches are given off from the dorsal
surface of the nerve. At the
upper part of the popliteal space, a large branch diverges from each
side of the nerve trunk to the
two heads of the gastrocnemius. Though usually given off as separate
branches, their intraneural
origin is from a bundle common to all of the above-mentioned muscles:
it has a rather long intraneural course, lying on the dorsal aspect of
this portion
1050
of the sciatic trunk.
Occasionally, the nerve to the soleus leaves the parent trunk in common
with the branch to the lateral head of the gastrocnemius. The branches
to the plantaris and
popliteus are usually given off individually but their intraneural
course is common with the
gastrocnemius and soleus fibers. Below the branches to the
gastrocnemius, a sensory branch is
given off, the communicans tibialis, which passes downward in the
sulcus between the two heads
of the gastrocnemius, becoming superficial in the calf by piercing the
deep fascia where it joins
the peroneal communicating to form the external or short saphenous
nerve, which supplies
sensation to the lower third of the leg on its outer side, and the
outer side of the foot and little toe.
The tibial nerve also gives off branches to the knee joint and to the
posterior tibial vessels.
The
posterior tibial nerve, the terminal portion in the leg of the
tibial (internal popliteal)
nerve, passes down the leg, occupying a deep position between the deep
and superficial muscles
of the calf, in a special compartment in the intermuscular septum
between these muscles,
accompanied by the posterior tibial artery and its venve comites, in
relation to which it holds a
superficial or dorsal position. In the lower part of the leg, it lies
medial and ventral to the tendo
Achillis; after passing behind the internal malleolus it enters the
sole of the foot, to terminate as
the internal and external plantar nerves. Immediately after the
posterior tibial nerve is formed by
passing through the arch of the soleus muscle, it breaks up into a
number of branches which
supply the lower portion of the soleus, the tibialis posticus, the
flexor longus digitorum and the
flexor longus hallucis.
The peroneal nerve (external popliteal), considerably smaller than
the tibial nerve, after
leaving the common sciatic trunk, at the apex of the popliteal space,
follows the lateral border of
the fossa and the medial margin of the biceps tendon. Passing over the
plantaris and lateral head
of the gastrocnemius. it winds around the neck of the fibula, where it
enters a canal in the origin
of the peroneus longus muscle, and breaks up into its terminal
branches.
In
the popliteal space, the peroneal nerve gives off the following
collateral sensory
branches, from the dorsal portion of its trunk: The communicating
peroneal which passes
medially across the lateral head of the gastroenemius.pierces the deep
fascia on the back part of
the leg and unites with the communicating tibial to form the short or
external saphenous nerve;
the sural branches, which may arise in common with the
communicating peroneal or at a lower
origin to supply the skin over the back and outer side of the calf and
leg. Intraneurally, the fibers
forming these nerves originate from a single bundle which occupies a
long intraneural course on
the dorsal surface of the peroneal portion of the sciatic trunk.
The
terminal branches of the peroneal nerve are given off after it swing
around the neck
of the fibula and passes through a canal in the peroneus longus muscle.
They are the
musculocutaneous, anterior tibial, and tibial recurrent. The anterior
tibial branch springs from
the lower portion of the flattened perneal trunk and has a long
intraneural course, composed of a
single bundle which in the upper part of the popliteal fossa lies in
the ventral portion of the
nerve. The musculocutaneous branch arises from the ventral portion of
the trunk and likewise
has a long, intraneural course, though composed of two bundles, one
1051
of which contains motor
fibers to the peronei muscles, the other containing the sensory fibers.
The
musculocutaneous nerve, lying at first between the peroneus longus
muscle and
fibula, passes obliquely downward and forward; it is deeply placed and
located in a fibrous canal
in the septum between the peronei and extensor longis digitorum; it
supplies the peroneus longus
and brevis with motor branches. In the middle of the leg it penetrates
the deep fascia and divides into an internal and external branch,
supplying the skin of the front of the leg and dorsum of the
foot and toes.
The
anterior tibial nerve, originating from the pleroneal between the
recurrent tibial and
musculocutaneous, passes downward and forward beneath the extensor
longus digitorum to the
ventral surface of the interosseus membrane, where it passes down the
leg accompanied by the
anterior tibial artery and its venae comites, lying between the
tibialis anticus and the extensor
longus hallucis. At the ankle it is crossed by the tendon of the
extensor longus hallucis, as it passes to the dorsum of the foot, where
it divides into its external and internal terminal branches.
The anterior tibial nerve supplies motor fibers to the tibialis
anticus, extensor longus hallucis,
extensor longus digitorum and peroneus tertius. Its external branch
supplies the extensor brevis
digitorum, and its internal branch the integument between the first and
second toe and a small
area on the dorsutm of the foot adjacent to these toes.
The tibial recurrent nerve, the
smallest, most anterior and highest of the
three terminal
branches of the tibial nerve, passes between the origin of the peroneus
longus and the fibula,
giving motor branches to the upper portion of the tibialis anticus and
articular branches to the
knee joint.
SURGERY OF THE SCIATIC TRUNK
In
war surgery injuries of the sciatic trunk are far more common than any
other nerve
lesion in the lower extremity. While severance of the entire trunk does
occasionally occur, this
incident is rare. The nerve to the hamstrings seldom shows complete
paralysis, and very
frequently the peroneal portion of the sciatic trunk alone suffers
injury. This is probably due to
the position of the peroneal in the sciatic trunk, where it occupies a
dorsolateral position and
tends to protect the tibial portion of the nerve. The components of the
sciatic trunk may suffer
injury in any part of their course in the buttocks, thigh. popliteal
space, or leg. Throughout its
entire course the tibial nerve is afforded greater protection than the
peroneal. The peroneal is particularly liable to injury in the region
of the head of the fibula, where it occupies a very
superficial position.
The
surgery of the sciatic trunk resolves itself into the surgery of its
component elements,
and not infrequently exposure will reveal the entire trunk extensivelv
involved in scar tissue
when clinically the lesion is confined only to its peroneal portion.
The surgeon must therefore be
governed by clinical indications rather than by the gross pathologic
appearance of the nerve at operation, and thereby avoid the sacrifice
of intact sciatic elements. Surgery of the sciatic trunk
resolves itself into the exposure of three regions, namely: For gluteal
lesions, upper thigh lesions,
and lower thigh lesions. In
1052
the gluteal region the
nerve is exposed by reflecting the gluteus maximus; in the upper thigh,
by
retracting the ischial head of the biceps medially; while in lower
thigh lesions this muscle is
retracted laterally. It is essential therefore that the surgeon be
familiar with the technique
involved in exposing the sciatic trunk in these regions; in addition to
this, he must be able to
appreciate and differentiate the component parts of the trunk, and, in
suture, to effect perfect
matching and alignment of its respective elements. The approximation of
the peroneal to the
tibial portion through torsion of the trunk would obviously be a
catastrophe, and though
neuraxon regeneration might progress unimpeded, the disturbance of
physiologic pattern would
give very confusing and unsatisfactory results. The sciatic trunk must
be considered not as an
individual nerve but as three distinct elements closely approximated in
a common sheath,
namely, from within outward, the nerve to the hamstrings, the tibial,
and the peroneal. The nerve
to the hamstrings seldom requires surgical intervention, while the two
remaining elements, the
tibial and peroneal portions, are commonly involved, though the two
latter are so separated by a
septal prolongation of the sciatic sheath that identification is
rendered possible and perfect
alignment facilitated by observing and maintaining the position of this
septum in suture. In this
respect, the sciatic trunk offers in the majority of cases a most
satisfactory means of effecting
physiologic approximation.
EXPOSURE IN
GLUTEAL
REGION
Exposure
of the sciatic trunk in the gluteal region is most satisfactorily
accomplished and
less trauma inflicted by dividing the tendon of the gluteus maximus at
its insertion into the femur
and reflecting it medially. This exposure not only assists in
preserving the nerve supply to the
gluteus maximus, but also is effective in avoiding the troublesome
hemorrhage associated with
across section of its fibers. The line of incision is curved, with its
base outward, and extends
from the posterior iliac spine outward and downward to the upper border
of the great trochanter
of the femur, and, slightly posterior, it passes downward over the
insertion of the gluteus
maximus tendon; it then curves backward, following the gluteal fold to
the midline of the thigh,
down which it may be extended over the course of the sciatic nerve, as
far as the individual
exposure necessitates. The deep fascia is exposed and divided in the
line of incision. Along the
upper border of the incision the fibers of the gluteus maximus are
split in their line of cleavage
and the tendon exposed and divided close to its insertion in the femur,
permitting a medial
reflection of the lower half of this muscle. In reflecting the gluteus
maximus, care should be used
to prevent injury to branches of the inferior gluteal vessels. To avoid
obscuring the field, these
vessels, when possible, should be caught and divided between forceps.
The sciatic trunk is now
exposed as it emerges from the great sacrosciatic foramen below the
pyriformis muscle, and
again care must be used to prevent injury to the inferior gluteal nerve
which emerges from under
the pyriformis along the dorsal surface of the sciatic trunk,
accompanied by branches of the
inferior gluteal artery and veins. To the medial side of the great
sciatic trunk lies the small sciatic
nerve, which may be differentiated from the nerve to the hamstrings by
following its course to
the lower border
1053
of the gluteus maximus,
where it becomes superficial. The nerve to the ham-strings in this
region may be either incorporated within the sheath of the sciatic
trunk or it may pass along its
medial side as a separate nerve. Electrical stimulation will readily
serve to identify this motor
branch when doubt exists. In this region the sciatic trunk is
surrounded by many vascular
branches, necessitating great caution; the reckless or blind
application of a hemostat in this
region to control an unseen bleeder may result in injury to important
motor branches. The
sciatic trunk may be followed beneath the pyriformis muscle, and for a
short distance within the
foramen, by upward retraction of the pyriformis. Even better exposure
may be had by dividing
its tendon and reflecting the muscle medially. After all vessels have
been carefully ligated to
avoid, as much as possible, the subsequent oozing. the tendon of the
gluteus maximus is sutured with strong linen. Drainage should always be
instituted for a period of 48 hours to care for
oozing, which is usually abundant following this exposure.
EXPOSURE IN THE THIGH
As
the sciatic trunk emerges from below the lower border of the gluteus
maximus, it
passes down the middle of the dorsum of the thigh,
FIG. 192.- Exposure of
sciatic trunk and
branches to the hamstrings resting upon the adductor in gluteal region;
insertion of gluteus maximus divided and the magnus, in close proximity
to muscle reflected, exposing the sciatic
nerve emerging from the greater sacrosciatic foramen below the
pyriformis muscle. A, the ribbon-like tendon of the
Gluteus maximus, lower portion reflected; B, nerve to hamstrings: C,
semimembranosus tendon; D, biceps, long
head; E, pyriformis; F, sciatic trunk; G, adductor magnus
resting upon the adductor magnus, in close proximity to the ribbon-like
tendon of the semimembranosus. The nerve trunk is fairly
superficial at the lower border of the gluteus maximus and at the popliteal space, where it is covered only by
an abundance of surrounding fat and the deep fascia. In the middle of
the thigh, however, the
sciatic trunk is diagonally crossed by the ischial head of the biceps
from within outward, the
nerve being deeply placed beneath the fleshy belly of this muscle.
1054
Exposure
of the sciatic trunk in the thigh is accomplished through a mid-dorsal
longitudinal incision, extending from a few centimeters above the
gluteal fold to the popliteal
space. The small sciatic nerve lies in close relation to the deep
fascia in this region and should be
identified and preserved if possible. While it is purely sensory and
not of great importance, its
identification and retraction will serve to prevent irritative
symptoms, following the accidental strangulation by suture, during
closure of the deep fascia. If the lesion be an upper thigh lesion,
the lateral border of the ischial head of the biceps is identified and
retracted medially, exposing
the flattened tendon of the semi-membranosus, which must not be
mistaken for the sciatic trunk, lying immediately along its lateral
border, surrounded by an abundance of fat. The lower border of the
gluteus maximus is undermined and retracted upward to afford higher
exposure and
if necessary a few of its fiber may be divided. In lower thigh lesions,
the medial border of the
ischial bead of the biceps is identified and retracted laterally
exposing the nerve below. Medial
or lateral retraction of the ischial head of the biceps will usually
permit
FIG.
193.- Exposure of
the sciatic in the middle and lower thirds of the a satisfactory
exposure of thigh by lateral retraction of the short head of the
biceps. Branches to the the sciatic trunk in any short head of biceps
is shown emerging from the lateral side of the peroneal division of the
sciatic trunk about the middle of the thigh. A, Semi-membranosus; B,
tibial nerve; C, biceps,
long head; D, branch to biceps, gluteus maximus. After short head; E,
peroneal nerve; F,
sciatic trunk
a satisfactory exposure
of the sciatic trunk in any part of its course below the gluteus
maximus. After identifying the nerve trunk, attention must
be given to its component parts. The nerves to the
ham-strings, passing along its medial border, must be identified and
carefully retracted medially
to prevent their injury during dissection of the trunk The sciatic
trunk in the thigh may present
itself as a single large nerve, or the division of its component tibial
and peroneal portions may be
conspicuous by their complete separation, or by markings on the sheath
of the trunk along their
line of cleavage. If inspection of the trunk fails to reveal
1055
any line of demarcation
between its respective tibial and peroneal portions, palpation, or
rolling
the nerve between the fingers, will usually serve in effecting this
identification. It should be remembered that the
component portions of the sciatic trunk are separated by a more or less
well-defined septal prolongation of its sheath; that its tibial
elements occupy a medial position,
somewhat more ventral than dorsal: that the peroneal portion , somewhat
more ventral than
dorsal; that the peroneal portion, which is the smaller of the
FIG. 194.– Diagrammatic
cross section of
sciatic trunk, showing its tibial and peroneal components. The septal
division between these portions of thee sciatic trunk does not, lie in
a strictly ventro-dorsal plane. The peroneal or
smaller division of the trunk occupies a ventro-medial position. A, A
type of sciatic nerve trunk in which the line of
division between its component parts is evident by a groove on the
surface of the nerve. B, Type in which separation of the component
parts is not so evident. (The above diagram represents the right
sciatic trunk as exposed through a dorsal incision;
the upper part of the diagram represents the dorsal surface of the
sciatic trunk)
two, is located in the
dorsolateral aspect of the trunk. The line of cleavage, therefore, will
not be
found in a strictly ventrodorsal plane, but passing from the center of
its dorsomedial quadrant to
its ventrolateral quadranit. Rotation of the sciatic trunk outward will
serve to rotate the plane of
the intraneural septum to a ventrodorsal position. Occasionally, it
will be necessary to find the
line of cleavage between the peroneal and tibial portions at their
division in the popliteal space,
from which point they may be carefully separated up
FIG. 195.- Method of
alignment in
physiologic approximation of the sciatic trunk, the intraneural septum
between
the peroneal and tibial porttions of the trunk serving as a guide to
alignment
the sciatic trunk. In
effecting such a separation, the septal division should be closelv
followed. There is no intercommunication of fibers between the
component elements of the sciatic trunk,
and this separation mav be accomplished, if executed with sufficient
care, without destruction to nerve elements. The septum dividing the
sciatic trunk into its component portions serves
admiraly as a guide in effecting physiologic alignment during suture.
Identification sutures in
the sheath of the nerve should be placed in a position to assure per-
1056
feet alignment of the
intraneural septum, and if it becomes necessary to disturb the
relationship
between one portion of thle trunk andi this septum, surface markings should be so
placed that identitication of this region is assured before
the original
relationship has been disturbed.
EXPOSURE OF THE
TIBIAL
NERVE (INTERNAL POPLITEAL) IN THE POPLITEAL SPACE
The
skin incision extends longitudinally through the middle of the
popliteal space, from a few
centimeters above its apex to a point, a few centimeters below the
union of the
two heads of the gastrocnemius. The deep fascia is divided, exposing
the fat of the popliteal
fossa. The tibial nerve should be identified as it emerges at the upper
part of the fossa from below the medial border of the biceps; its
distal portion is identified as it passes below the union
of the two heads of the gastrocnemius. Having located the nerve at
these two points, it may be
followed through the popliteal space by dividing the overlying fatty
tissue. Several vascular branches will be met and
divided between clamps to prevent obscuring the field. A careful
exposure in this way will usually avoid injury to the popliteal
vessels. The small saphenous vein
joins the popliteal vein about the middle of the fossa and will require
ligation. Near the apex of
the popliteal space the tibial nerve gives of diverging motor branches
to the two heads of the gastrocnemius. These
FIG. 196.- Exposure of the
external and
internal popliteal nerves in the popliteal space. A,Tibial nerve; B,
internal
hamstring tendon; C, branch to gastrocnemius, medial head; D, branch
to gastrocnemius, lateral head; E, branch to
soleus; F. Gastrocnemius, medial head; G, tibial communicating nerve;
H, lateral hamstring tendon; I, peroneal
nerve; J, peroneal communicating; K, sural nerve; L, gastrocnemius,
lateral head
.
branches originate from
a common bundle on the dorsal surface of the nerve, which by
intraneural dissection may be followed some originate from a
common
bundle on the dorsal surface of the nerve, which by intraneural
dissection may be followed some distance up this portion of the sciatic
trunk. These branches by
their intraneural localization identify the dorsal surface of the
tibial nerve. Occasionally, one of
the branches of the gastroenemius will
1057
carry fibers to the
superficial fibers of the soleus: at other times the branch to the
soleus is given
off from the tibial trunk at a lower level. Intraneural dissection
reveals this branch, however, it
may reach the soleus, as Springing from the common gastroenemius
bundle. A small branch to
the plantaris may be given off directly from the tibial trunk or from
the branch to the lateral head of the gastrocnemius.
After the nerve has passed below the gastrocnemius, a small branch is
given to the popliteus muscle. Shortly after the divergence of the
motor nerves to the two heads
of the gastrocnemius, a sensory branch, the communicating tibial,
leaves the tibial trunk and
passes in the sulcus between the two heads of the gastrocnemius to
pierce the deep fascia and
enter into the formation of the external saphenous. Branch
identification in the popliteal space should at least
include the branches to the gastrocnemius and soleus, and the tibial
communicating. The identification of each is simplified by its course,
the nerves to the
gastrocnemius diverging respectively to its medial and lateral heads;
the communicating tibial by
its superficial course. If access to the tibial nerve is desired below
the popliteal fossil, the line of
cleavage between the two heads of the gastrocnemius may be split as far
down this muscle as necessary without
disturbing its nerve supply. With the retraction of the lateral and
medial
head of the gastrocnemius, the tibial nerve may be readily followed to
the point where it
disappears under the tendinous arch of the soleus, accompanied by the
popliteal vessels.
SURGERY OF TIHE POSTERIOR TIBIAL NERVE
A
certain number of lesions of the posterior tibial nerve are over
looked, because patients
frequently ignore the intrinsic paralysis and anesthesia of the sole of
the foot. There are, however,
certain lesions which are associated with marked irritative symptoms
referred to the sole of the
foot, and these, in many instances, are peculiarly resistant to the
moderating effect of time and
sedative treatment, and occasionally require neurolysis, alcohol
injection, or even excision of the
posterior tibial nerve. The writer has observed one instance in which
the painful svndrome in the
sole of the foot persisted after a neurolysis of the posterior tibial
nerve and a subsequent alcohol
injection, and was later relieved by a decortication of the popliteal
artery. In the lower part of the popliteal space several
branches pass from the tibial trunk to the popliteal vessels: these
branches follow the vessels through the canal in the soleus and are
probably active to some
degree in the production of irritative phenomena. In effecting a
decortication of the popliteal
artery the denudation should proceed to the opening in the soleus
muscle by splitting and
retracting the heads of the gastrocnemius.
As
the tibial nerve passl's throughl the tendinous arch of the soleus to
become the
posterior tibial, it divides into two branches, the dorsal of which
immediately breaks up into at
number of branches to supply the ventral surface of the soleus,
tibialis posticus, flexor longus
digitorum, and flexor longus hallucis. The other branch of the nerve
passes down the leg in a
compartment formed by the intermuscular septum, separating the
superficial from the deep calf muscles,
accompanied by the posterior tibial artery anol its vena, comites. In
the lower third
of the calf it is more superficial, lying to the medial side of
1058
the tendo Achillis and
covered by the deep fascia. In this region the nerve is composed of two
bundles, which ultimately go to the formation of its terminal internal
and external plantar
branches.
Exposure
of the posterior tibial nerve in its deep position in the upper
two-thirds of the
calf is best accomplished through a mid-dorsal incision, extending from
the middle of the
popliteal space to the lower third of the leg, where it curves somewhat
to the medial border of the
tendo Achillis. In exposing the deep fascia care should be used to
avoid injury to the tibial
communicating branch of the tibial nerve, which unites in the middle of
the calf with the peroneal communicating
branch to form the external saphenous nerve. Injury to this branch,
which is sensor! in function, is productive of but little disturbance,
but when a lesion is already
associated with a certain amount of anesthesia it is not wise to easily
sacrifice other sensors
branches. Identification and isolation of this nerve is also important,
in that with closure of the deep fascia it mav be
caught in the sutures, resulting in considerable pain and possible
irritative
phenomena. The short saphenous vein is also encountered and should be
ligated to prevent
tearing and troublesome hemorrhage. The incision is now carried through
the deep fascia, and the
gastrocnemius bisected, from the point of union between its two heads
to the tendo Achillis and
widely retracted, exposing the soleus muscle below. The soleus muscle
is now bisected in the same way exposing
the intermuscular septum below. It will be remembered in splitting the
soleus muscle that it has an aponeurosis covering its dorsal surface,
which must not be mistaken
for the underlying intermuscular septum. Both gastrocnenmius and
soleus, now having been
longitudinally bisected from their origin to the tendo, Achillis are
retracted, exposing the deeply placed
intermuscular septum, separating the superficial muscles from the deep.
The
posterior tieial nerve and its accompanying artery and vein will be
found by splitting the fascia
along the medial border of the flexor longus hallucis muscle. The close
proximity of the
posterior tibial nerve to its accompanying arterial structures renders
its dissection rather tedious,
because of the frequent tearing of veins. The simplest procedure to
follow is: Ligation or clamping of veins in the
lowest part of its course; in the upper part, compression of the
posterior
tibial artery, thus greatly facilitating isolation of the nerve.
In
the lower third of the leg the tibial nerve may be located along the
medical border of
the tendo Achillis by dividing the deep fascia, extending from the
tendo Achilles to the deep
muscles. The nerve will be found lying between the flexor longuts
digitorum and the flexor
longus hallucis.
EXPOSURE OF THE
PERINEAL
NERVE (EXTERNAL POPLATEAL) IN THE POPLITEAL SPACE
The
incision extends from the apex of the popliteal fossa, following the
medial border of
the external hamstring tendon; it passes around the neck of the fibula,
and, for a short distance
down the anterolateral surface of the leg midway between the crest of
the tibia and fibula. The
deep fascia is divided in the line of the incision; as it approaches
the head of the fibula, this fascis
1059
will be found to be
greatly thickened and great care should be used in its division to
prevent
injury to the nerve, which lies immediately under its deep surface and to which it
may be adherent. The nerve should first be located at the apex of the
popliteal fossa, where it leaves the sciatic trunk, and followed along,
the border of the
biceps tendon. As it crosses the plantaris and the lateral head of the
gastrocnemius the peroneal nerve becomes greatly flattened, which shape
it retains in its passage
around the neck of the fibula under cover of the peroneus longus, where
it breaks up into its
terminal divisions.
In
the popliteal fossa the peroneal nerve gives off sensory branches. The
peroneal comunicating is the
superior branch and crosses the head of the gastrocnemius muscle toward
the
posterior aspect of the calf, where it perforates the deep fascia and
joins with the tibial
communicating to form the external saphenous nerve. A short distance
below the peroneal communicating the sural branch or branches are given
off, supplying sensation to the external
surface of the leg. Occasionally the sural branches leave the tibial
trunk with the peroneal com unicating,. These sensory branches bring
from the dorsal aspect of the tibial trunk and have a
long, combined intraneural course.
FIG. 197.- Exposure
of external popliteal ind
its terminal division as it swings around the neck of the fibula, the
insertion of the peroneus longus having been divided to expose the
terminal branches. A, Lateral hamstring tendon;
B, head of fibula; C, origin of peroneus, divided; D, peroneal
communicating; F, sural nerve; G, peroneal nerve; H,
anterior tibial nerve; I, tibial recurrent ; J, musculocutaneous nerve,
K, branches to peronei; L, musculotaneous,
sensory portion
In the upper part of the
popliteal fossa the peroneal nerve is composed of four bundles, the
most
dorsal of which contains the sensory fibers of the peroneal
communicating and sural nerves. Below this sensory bundle, two bundles
are found, one of which contains motor fibers to the
peronei muscles, the other containing sensory fibers to the
musculocutaneous nerve. Below
these, in the ventral part of the nerve trunk, lies a bundle which
contains fibers for the anterior
tibial nerve. As the nerve proceeds along the lateral border of the
popliteal fossa and the dorsal
cutaneous bundle is given off in the formation of
1060
the peroneal
communicating and sural nerves, it undergoes a degree of torsion and
flattening in
passing over the lateral head of the gastrocunemius, so that the three remaining bundles
lie side in a mediolateral plane: the most medial bundle now being,
that
which ultimately forms the anterior tibial nerve, the two lateral
bungles, soon to unite, form the
musculocutaneous nerve--the more lateral bundle containing the motor
fibers to the peroneal
muscles, the medial bundle, the sensory fibers to the musculocutaneous.
As the flattened trunk passes around the
head of the fibula, the lateral hundlle forms the musculocutaneous
nerve
and the dorsal. or lower, bundle forms the anterior tibial and tibial
recurrent nerves.
Exposure
of the terminal branches is accomplished by carefully dividing the
fibers of the
peroneus longrus at its origin, as thle nerve is followed around the
bone. Occasionally it is
possible to effect suture of the individual branches as in the
posterior interosseous nerve, where it
fans out; beyond this point, reconstruction becomes increasingly
difficult.
Physiologic
approximation of the peroneal nerve is greatly facilitated by the
position of
its branches and the flattened or ribbonlike shape of the nerve in the
lower part of the fossa and
as it passes around the neck of the fihula. In the upper part of the
popliteal fossa, the dorsal
surface of the nerve is definitely indicated hiy the position of its
sensory branches. In this
position the nerve is oval in shape, its longest axis being in a
ventro-dorsal plane. As it passes over the lateral
head of the gastrocnemius, the dorsal quadrant of the nerve is rotated
to a
lateral position. which in passing around the neck of the fibula
becomes ventral and superior, and
from this ventral border the musculocutaneous nerve is given off. The
dorsal part of the nerve,
which is now inferior, becomes the anterior tibial, which gives off the
tibial recurrent nerve. Though most writers
describe the tibial recurrent nerve as one of the terminal peroneal
branches,
its intraneural course is common with the bundle containing anterior
tibial fibers. With a
visualization of the natural torsion occurring in the peroneal trunk
in the popliteal fossa and as it
winds around the neck of the fibula, and with the assistance afforded
by the flattened shape of the
nerve trunk, the surgeon should have little difficulty in effecting
physiologic approximation.
CONTINUITY DEFECTS
Relatively
large defects in the sciatic trunk and its terminal external and
internal popliteal
portions may be overcome by flexion relaxation of the knee, providing
these nerves are
extensively mobilized, particularly in the popliteal fossa. There is no
type of transposition which
can he used in the lower extremity to shorten the course of these
nerves. Defects, therefore,
uncorrected by primary stretching and flexion relaxation, if at all
correctable, will probably yield only to secondary
stretching, i. e., the two-stage operation, in which the unsectioned
nerve
ends are united, after full advantage is taken of primary stretching
and flexion relaxation, by
xtensive liberation of the nerve trunk in both directions. In the
writer's experience, several cases
were encountered in which approximation seemed hopeless at the primary
operation, and grafting was resorted to. In each
instance regeneration failed, but in a subsequent
1061
operation end-to-end
suture was effected by the two-stage method. We believe that the
two-stage
operation will probably be found efficacious in approximating any
correctable defect, and that
grafts should be resorted to only after the two-stage operation has
failed, certainly never before it
has been attempted. When end-to-end approximation has been despaired
of, and in cases of
incorrectable regenerative failure, the disability, in so far as ankle
instability and drop-foot are
concerned, may be fairly well corrected by arthrodesis or tendon
transplantation. (See irreparable
defects, p. 9.59.)
SECONDARY SUTURE
Defective
regeneration in sciatic lesions, as in other nerves, may be due either
to defective
neuraxon, or defective muscle regeneration: it is utmost importance, in
considering the question
of secondary operation, to determine the degree of responsibility of
each. In approximately 85 per
cent of complete sciatic trunk sutures, plantar flexion of the foot
returns to some degree through regeneration in the
gastrocnemius-soleus group. In about 40 percent of cases, some
voluntary
power, after a four-year period, is observed in the peroneus longus and
tibialis posticus. In about
30 per cent, some flexion of the toes is observed, while return of
voluntary movement in the
tibialis anticus and extensor of the toes is found in less than 20
percent. In no case has the writer observed a regeneration
of the intrinsic foot muscles, following sciatic suture or suture of
one of
its terminal branches. In approximately 80 percent of suture cases
there has been return of
sensation, to some degree, in the foot, though rarely, after four
years, has the writer observed a
complete disappearance of anesthesia, though in most instances trophic
disturbances and pressure sores have ultimately
healed. In the majority of instances in which anesthesia his
disappeared,
discriminative sensation has not been recovered, the anesthetic zone
having been replaced by a
type of nondiscriminatorv sensation, which is usually interpretedl by
the patient as tingling; there
seems, however, to be a tendency toward a gradual sensory improvement.
A few of these patients find it possible to
distinguish between hot and cold water when taking a bath, but are
unable to
localize touch, or discriminate between a dull and sharp point. A study
of these regenerative
defects throws important light upon both muscle and nerve regeneration.
Neuraxon
regeneration is demonstrated by Tinel's sign and in most instances is
found to
be present in some degree. When Tinel's sign is totally absent below
the suture line, or is greatly
diminished in intensity, after six months, a defective suture is
probatbly accountable. This is
particularly true when pressure over the suture line elicits a strong
reaction; in such instances secondary suture is
indicated.
In
a number of cases, percussion of the peroneal nerve over the head of
the fibula has
elicited tingling, localized on the plantar surface of the foot. This
indicates that the tibial portion
of the nerve during suture was probably united to the peroneal, in that
tibial sensory fibers are
present in the peroneal trunk. In other instances, the writer has
observed plantar flexion of the
foot when the patient was attempting dorsollexion, which was perhaps
due to the
1062
presence of peroneal
motor fibers having reached the gastrocnemius. The presence of some
regeneration in the gastrocnemius in about 80 per cent of cases can be
accounted for in two ways: First, this
muscle, because of its large size and high innervation, receives a
certain number
of regenerated motor fibers; second, because of the drop-foot, it is
seldom overstretched as are
the extensors of the anterolateral group. The failure of recovery in
the tibialis posticus and
flexors of the toes indicates that overstretching is not entirely
responsible for these motor defects,
which in all probability are due to an extreme degree of muscular
degeneration and atrophy
following prolonged denervation. The failure of muscle regeneration in
the intrinsic foot muscle can probably be
accounted for by extreme muscular degenerative changes, due to their
small
volume and distal position. We have not observed a single instance of
regeneration in the
intrinsic foot muscles, following a paralysis lasting longer thran 18
months. Even in cases of
spontaneous regeneration. or after a neurolysis, with probably no
disturbance of nerve pattern and
in which sensation was fully recovered, the intrinsic foot muscles
failed to show any signs of
regeneration and their extreme atrophy persisted.
The
frequent failure of regeneration in the extensors of the anterolateral
group, namely,
tibialis anticus, extensor longus hallucis, and extensor longus
digitorum, requires special
comment. A number of cases have been observed, following suture and
neurolysis of the
peroneal nerve, in which the anesthetic areas showed much improvement,
without a restoration
of motor function in these muscles, while voluntary power was observed
to have returned in the peroneus longus.
Instances of this kind can be explained only on the ground of muscle
stretching
due to foot-drop, which the peroneus longus escapes, the anatomical
couIrse of its tendon behind
the external malleolus. In several such cases, lengthening of the
gastrocnemius tendon, with
splinting of the foot in dorsoflexion, has in a short time from one to
three month, resulted in
return of voluntary power in the tibialis anticus and to a less degree
in the extensors of the toes.
The
defect in peroneal lesions presenting a return of voluntary power in the peroneus longus,
without a corresponding recovery in the tibialis anticus, may with
reason be
attributed to the evil effects of overstretching. A failure of
regeneration in the peroneus longus,
however, indicates that extreme degree of atrophy and miuscle
degeneration which is so
commonly found in the legg following prolonged sciatic paralysis: this
regenerative muscular
failure is also, commonly observed in the smaller muscles on the
dorsurm of the leg. It maybe roughly stated that
between 40 and 50 percent of failures in the return of dorsoflexion of
the
foot are due to overstretching.
There
is a marked tendency for the gastrocnemius to develop contractures in
all sciatic
trunk lesions, as well as terminal peroneal lesions. The prevention of
these contractures and their
correction after development is of extreme importance. A patient with a
sciatic or peroneal
paralysis should be provided with a satisfactory foot-drop splint and
the importance of its use
strongly emphasized. Not only should a splint be applied to the shoe
for day wear, but there should also be
provided a night, splint, and its persistent use should be
1063
insisted upon. When
contracture in the gastrocnemius has definitely developed, lengthening
of
the Achilles tendon should not be postponed and the patient trained to
assume, when sitting, a
position which the writer has termed in his clinic, for convenience,
“Achilles corrective habit
posture, " in which the patient stretches the Achilles tendon by
resting
the anterior part of the foot
on the floor with the knee overflexed, exerting pressure by the weight
of the opposite leg when
crossed over the knee--the common habit of sitting with the knees
crossed: the common habit of
sitting with the knees crossed; i.e., the injured foot, while resting
on the floor, is drawn backward in a position causing tension on the
Achilles tendon, which is stretched by the superimposed weight of the
opposite
leg. The development of this habit corrective posture has proved of
great
value in stretching the Achilles tendon and relaxing the extensor
muscles.
Secondary
sutures should be attrempted only for the correction of defective
neuraxon
regeneration, or for marked degrees of torsion. In resuturing the
sciatic trunk or its terminal
portions, identification sutures are not to be employed for surface
identification, as the nerve may
have suffered torsion in the original suture. In the sciatic trunk, the
intraneural septum between
its component tibial and peroneal portions will serve as a reliable
guide in effecting physiologic
approximation. In the popliteal portion of these nerves, anatomic or
branch identification will
serve in the correction of defects caused by torsion. (See technique
for sciatic trunk and popliteal
lesions, pp. 1051-56.)
SUPPLEMENTARY PROCEDURES FOR IRREPARABLE
DEFECTS AND DEFECTIVE REGENERATION IN THE SCIATIC TRUNK AND IT'S
TERMINAL DIVISIONS
Though
complete anesthesia of the foot follows total paralysis of the sciatic
trunk the
sensory disability alone does not seriously interfere with locomotion.
Undoubtably, the greatest
factor in the disability following complete sciatic paralysis is
referable to the motor side. The loss
of sensatition in the foot, however predisposes to traumatic insults,
and a continued irritation of a
traumatisized anesthetic area may be serious in its consquences-through
pressure sores are not
usually so and will readily heal when he irritation is relieved.
In
a series if more than 300 sciatic lesions. not a single instance was
observed in which it was not
possible to effect approximation of at least the tibial portion of the
sciatic trunk; in about 80
percent of cases followed, there has been a restoration if motor
function
to
some degree, with at gradual disappearance of pressure sores. The more
defect consists briefly in
the loss of stability in the foot. In the majority of instances
following sciatic suture, there has
been a return of least of at some useful power in the gastrocenemius,
rendering plantar flexion of the foot
possible, which assists in correcting much if the original disability.
It is
obvious that the tibial nerve from a functional standpoint is of more
importance than the
peroneal, and in continuity defects of both nerves resisting correction
by every other means, the
surgeon is justified in sacrificing the peroneal portion of the trunk,
when the defect in the tibial
can be corrected by the use of the peroneal as a transplant, in an
efffort to restore at least,
gastrocnemius function and sensation to the sole of the foot.
1064
VIABLE NEUROPLASTIC TRANSPLANT FOR THE
CORRECTION OF TIBIAL DEFECTS
First
stage.- In this procedure, to assure viability of the graft, a
two-stage operation is
done, in which the proximal end of the sciatic trunk first receives
attention. At the lower end, the
line of cleavage between the peroneal and tibial portions is found and
these respective elements separated for a short distance up the sciatic
trunk. The ends of both nerves are now resected
until normal appearing nerve bundles are found, they are then brought
together and carefully approximated, making a loop of the distal end of
the proximal segment of the sciatic trunk. The sciatic trunk is now
followed upward for a distance a little longer than that necessary to
fill
the defect; at this point the line of cleavage between the peroneal and
tibial portions of the nerve
is identified
FIG. 198.- This and Figure
199 illustrate
viable neuroplastic transplant for repair of tibial portion of sciatic
trunk in
irreparable lesions of both divisions. A, Exposure of proximal end of
sciatic trunk; identification sutures placed; B,
neuroma resected from both divisions: C, tibial and peroneal portions
separated in line of cleavage to permit end-to-end approximation; D,
end-to-end approximation uniting proximal end of tibial division to
proximal end of peroneal
division; E, peroneal division divided to permit degeneration of
peroneal fibers in that portion of the trunk to be used as a transplant; upper
end
of peroneal portion injected with alcohol to prevent regeneration of
peroneal fibers in transplant; F, peroneal transplant now becomes a
viable part of the tibial portion of the nerve and
presents a neuroma, showing complete migration of tibial fibers; G,
transplant turned down and united to distal end
of tibial division, filling the defect--peroneal portion having been
sacrificed to repair the tibial. (See fig. 190)
and separated for a
short distance to permit division of the peroneal portion. The purpose
of
this step is to permit degeneration in the anastomosed segment of the
peroneal nerve, which is later to be reflected downward and attached to
the distal segment of the tibial nerve as a viable
transplant. This procedure will allow regeneration of the tibial fibers
around the loop and tip the intact transplant.
The upper end of the peroneal nerve, proximal to the point where it is
divided, is now injected with alcohol, or foreign tissues interposed to
prevent regeneration of
peroneal fibers shown that portion which is to be used as a transplant.
In this way, the viability
of the transplant is assured during migration of tibial fibers.
If
the transplant to be utilized is 6 inches long, the second stage of the
operation is
postponed for a period of seven months, allowing regeneration to
proceed at the rate of 1 inch per month plus one month’s grace. If the
transplant
1065
FIG. 199
1066
plant is longer or
shorter, the time of the second operation will be modified accordingly.
Second
stage.- The sciatic trunk is again exposed above, and the
tibial nerve
below; and
a favorable bed prepared to receive the regenerated transplant. The
loop at the end of the sciatic
trunk is isolated with great care and the line of cleavage between the
tibial and peroneal (now
transplant) portions of the trunk carefully separated up to a point
where the peroneal was
originally divided: the transplant is now turned down. The upper
segment of the tibial nerve, with its vialble
transplant attached, is accurately approximated to the distal segment
of the
tibial nerve, after the scar tissue of both ends has been carefully
resected. If the branches to the
gastrocnemius are properly preserved, and their dorsal position in the
tibial trunk borne in mind,
and the approximation with the transplant is planned without torsion, a
return of function in the
gastrocnemius and sensation to the sole of the foot may be expected.
Inasmuch
as voluntary dorsal flexion of the foot is permanently lost, the
drop-foot may be
corrected by arthrodesis of the ankle joint or tendon slinging--no
muscles being available to
restore by tendon transplantation the lost function of the
anterolateral group of muscles supplied
by the peroneal nerve. Artrodesis stabilizes only the posterior portion
of the foot without giving
support to the toes; in certain eases it seems to be valuable but
occasionally it is attended with end results
entirely unsatisfactory to the patient. Tendon slinging is by far most
satisfactory
of these procedures for the correction of drop-foot in irreparable
nerve lesions. It consists in
suspending the foot by passing the upper part of the tendon of the
tibialis anticus and peroneus
longus through a hole in the shaft of the tibia. where thev are
anchored; and supplementing this suspension with the
peroneus brevis; the extensor tendons of the toes are used to suspend
the
anterior part of the foot.
TECHNIQUE
A
long incision on the anterolateral surface of the leg, midway between
the crest of the
tibia and the fibula is carried down to the ventral aspect of the
ankle joint, mid-way between the
two condyles. As it reaches the annular ligament it curves to the outer
side of the foot, below
the external malleolus, to expose the peronei tendons. The tendon of
the tibialis anticus is now
isolated, and freed from muscle fibers to a point about 6 inches above
the annular ligament. The tendons of the
extensors longus halluctis and digitorum are treated in a similar
manner. The peronei tendons are exposed by undermining the lateral
border of the incision;
after being mobilized. they are divided at the upper end of the
incision. They are again exposed
and their sheath opened on the lateral border of the foot; after having
been. withdrawn from their sheath they are
directed anterior to the condyle, through a passage made under the
annular
ligament. A hole through the crest of the tibia is now made by a gouge,
the tendon of the tibialis
anticus drawn through from the medial side, and the tendon of the
peroneus longus passed
through from the lateral side, with the foot held in dorsal flexion, at
a right angle to the tibia, and
neutral to inversion and eversion, the tendons are drawn taut, the
angle of flexion being slightly
overcorrected: they are then fixed with strong linen sutures. Experience
1067
has shown that
it is advisable to supplement this procedure by also suspending the
tendons of the peroneus brevis, extensor longus digitorum, and extensor
longus hallucis; which is
effected by suturing them to the transplanted tendons of the tibialis
anticus and peroneus longus,
the combined group of tendons being too large to be passed through the
hole in the tibia. It is
essential that the foot he kept slightly overflexed and straight, and
each tendon attached individually, after its
tension has been properly adjusted. After six weeks, the plaster cast
may be
disregarded: at shoe fitted with a drop-foot splint should, however, be
worn during the day and a
drop-foot bed splint used at night. Walking on the foot without a
suitable drop-foot splint should
not be permitted until after the third or fourth month, by which time
the tendons should be firmly fixed in hardscar
tissue.
FACIAL NERVE
FACIAL PARALYSIS
Most
surgical lesions of the periphleral portion of the facial nerve are
found in its course through
the facial canal in the temporal bone, where it is occasionally
involved in
skull fractures or injured during operations for mastoid disease. Its
most frequent affection,
however, is that type of facial paralysis termed Bell's palsy, with a
common history of exposure
to cold. Its long course through the facial canal, which it almost
completely fills, renders it
particularly susceptible to injury or disease in this region; it may be
completely severed or
crushed by fragment of bone during a mastoid operation, or compressed
by inflammatory
exudate, hemorrhage, or congestion. Bell’s palsy is a compression
paralysis due to congestion or
inflammatory affection from exposure. Congestion of the facial nerve in
this region is
particularly serious because the nerve is unable to expand, being
completely surrounded by a
bony wall, and any congestion or inflammatory exudate
FIG. 200.- Dissection of
temporal bone, showing course of facial canal in its vertical and
tympanic portion--wire directed through canal; anterior to the nerve
lies the tympanic cavity. Note the straight course of the nerve from
its position anterior and below the eminence of the
lateral semicircular canal to the stylomastoid foramen. Identification
of the nerve at these two
points--just below the lateral semicircular canal and at the
stylomastoid foramen--is the keynote to
the exposure of the nerve through its vertical course. (Ney. The Laryngoscope,
1922)
is rapidly converted
into a compressive agent. The nerve, after its exit from the
stylomastoid
foramen, is occasionally injured by stab or gunshot wounds; as it
passes through the parotid
gland it may be compressed by suppurative processes or neoplasms.
Injuries distal to the parotid
gland, unless very extensive, seldom implicate the complete nerve,
usually involving only one or
more of its terminal branches.
May
facial palsies of the compressive type recover spontaneously, as the
congestion or
inflammatory exudate responsible for the paralysis subsides. After
surgical division during
mastoid operations, if the facial canal is no blocked
1068
by bone fragments or
scar tissue, the nerve will usually regenerate. If spontaneous
regeneration
progresses satisfactori1y, the facial muscles should show signs of
recoverv before one vear, and
in each instance this period should be allowed to lapse lefore a
decision of nonregeration is
definitely made. During this expectant period it is essential that the
facial muscles be properly splinted to prevent
overstretcihing. which frequently is responsible for much delay in
muscle
regeneration.
NERVE ANASTOMIOSIS IN FACIAL PARALYSIS
Frequent
attempts have been made to correct facial paralysis by anastomosing the
spinal
accessorv or hypoglossal nerve to the facial. In this procedure the
facial nerve is exposed at its
exit from the stylomastoid foramen and divided ; the hypoglossal or
spinal accesssory, whichever
may be selected, is next exposed and divided and its proximal end
approximated to the end of the distal segment of the
facial. The regenerating spinal accessory or hypoglossal fibers will
now
pass through the peripheral facial trunk to the facial musculature;
after a period of five or six
months these muscles will regain their tone providing regeneration has
been satisfactory--and the
face will show great improvement during repose. The facial muscles,
however, fail to react to emotional expression,
anl to all intents and purposes remain totally inactive until called
into play
by spinal accessory or hypoglossal impulses. If hypoglossofacial
anastomosis has been done, the
facial muscles will contract vigorously during mastication and
deglutition ; after facio-accessory
anastomosis, the facial muscles will react during turning of the head
or elevating of the shoulder. These facial movements,
following facial nerve anastomosis, are entirely irrelevant to
emotional
expression, and occasionally are extremely embarrassing, in attempts to
swallow or lift the
shoulder will inaugurate winking or drawing up the angle of the mouth.
Some writers have
recommended the use of the hypoglossal nerve for anastomosis in facial
paralysis in preference
to the spinal accessory on the ground that anatomic proximity of the
facial and hypoglossal center in the cortex
might facilitate reeducation. Experience seems to indicate that the
conversion of the hypoglossal center to facial function is not readily,
if ever, accomplished. Ney
has not observed a single instance of nerve anastomosis in which any of
the coordinated
movements required in facial expression have been regained, though he
has had under his
observation several cases which, for a period of eighteen months,
received constant daily
instruction under, the direction of experienced teachers. It has been
possible to train certain
favorable cases to a point where they would be able to effect
satisfactory isolated closure of the
eye, Or contraction of the muscles about the corner of the mouth,
without synchronous
movements in the shoulder or tongue; coordinated emotional movements
however, were totally
lacking in spite of all reeducative enleavors; the hypoglossal or the
spinal accessory fibers remain hypoglossal or
spinal accessory fibers from a functional standpoint and probably never
will be able to subserve any other function. The most that may be said
in favor of nerve
anastomosis for the correction of facial paralysis is that, in
favorable cases, there will be a
restoration of tone in the facial muscle; it is usually associated with
more or less embarrassing
incoordinated facial movements
1069
which are incited
by hypoglossal or accessory stimuli. The operation of nerve anastomosis
for the correction of facial paralysis is now being generally abandoned.
The
possibility of recovering coordinated emotional expression in the
paralyzed facial
muscles probably lies only in restoring the physiologic continuity of
the facial nerve. This
procedure has generally been considered impractical from a surgical
standpoint, because of the
difficulty involved in isolating, and repairing the facial nerve. Ney,
however, has devised a
technique by which the facial nerve may be satisfactorily exposed and
repaired in that portion of
the facial canal where it most frequently suffers trauma, namely , in
its vertical or tympanic
segment.
TECHNIQUE OF EXPOSURE AND REPAIR OF THE
FACIAL NERVE THROUGH IT'S COURSE IN TIHE TEMPORAL BONE FROM THE GENU OF
THE FACIAL CANAL TO THE STYLOMASTOID FORAMEN
The
incision corresponds to that commonly used in the radical mastoid
operation, except
that it is extended forward, above the ear, to expose the zygomatic
tubercle: below it is extended
from 1 to 2 inches beyond the mastoid tip, following the anterior
border of the sternomastoid
muscle. Through this incision the mastoid bone is exposed and the soft
parts reflected from the entire mastoid process,
completely exposing the mastoid tip, during which care should be used
to
prevent injury to the nerve as it emerges from the stylomastoid
foramen. The soft parts should be
thoroughly freed from the under surface of the auditory process of the
tympanic plate. The stylomastoid foramen is
located about 7 millimeters in front of the tip of the mastoid; its
depth from this point varies
considerably, depending upon the extent of mastoid development. In
infants, before the mastoid has developed. the facial nerve emerges
from the stylomastoid
foramen directly on the surface of the skull, where it may be injured
in the application of forceps. With the development of the mastoid the
stylomastoid foramen becomes covered with the mastoid tip and the
auditory plate of the tympanic ring. The cartilaginous portion of the
external
auditory meatus is entirely separated from its bony wall, except in its
anterior portion. Its
attachment to the auditory process is usually firm, because of the
roughened character of the bone
in this region. It is important, however, that the auditory plate be
well exposed.
The
auditory plate of the tympanic ring is now removed by a sharp chisel or
strong
rongeurs. This removed should be executed with considerable care to
prevent fracture, of the
tympanic ring the bone being cut down rather than broken down. The
removal of the tympanic
plate is the key to the situation so far as locating the stylomastoid
foramen is concerned. The auditory process now
having been removed, the operator may proceed with the removal of the
mastoid cortex
and cells. The mastoid antrum is located as in the usual mastoid
operation. The mastoid cells are now thoroughly removed, endeavoring to
keep the cavity as shallow as
possilble by trimming down the rim left by their evacuation; this is
particularly important in the
suprameatal region, where the cortex and cells of the posterior zygoma
should be removed
completely as far
1070
FIG. 201.- Primary incision
and exposure of the
mastoid tip, suprameatal ridge, superior, posterior, and inferior bony
mestal walls. The chisel shows point at which removal of auditory plate
is begun, to permit exposure of the
stylomastoid foramen. (Ney. The Laryngoscope, 1922)
1071
FIG.
202.- Auditory
portion of the tympanic bone, partially removed, exposing the exit of
the
facial nerve from the stylomastoid foramen to where it passes into the
substance of the parotid
gland. Mastoid cortex removed and cells evacuated-probe passed into
antrum; suprameatal ridge
partly removed. (Ney. The Laryngoscope, 1922)
1072
FIG. 213.- Bridge formed by
the posterior
meatal wall broken down over antrum,exposing the eminence of the
lateral
semicircular canal;.suprameatal ridige not sufficiently broken down.
(Ney. The Laryngoscope, 1922)
1073
forward as the
zygomnatic tuberle. Frequently it is necessary to expose the dura to
gain
sufficient, depth in this relgion.
The mastoid tip is
entirely removed and the facial nerve exposed as it emerges from the
stylomastoid foramen.
Occasionally the localization of the nerve is attended with some
difficulty; its identification is often facilitated by palpation, when
it is felt as a tense cord passing
from the stylomastoid foramen to the parotid gland. The difficulty
usually lies in attempting to locate the nerve in the region of the
mastoid tip, when in the majority of instances it is to be
found anterior to the tip. The posterior meatal wall may
FIG. 204. - Facial nerve
uncovered through a
portion of its vertical and tympanic course, showing method of breaking
down the wall with a fine, sharp chisel. (Ney. The Laryngoscope, 1922)
now be reduced to the
level of the mastoid evacuation; that portion overlying the mastoid
antrum
is entirely removed. If an attempt is made to break down the antrum
with at chisel, great care
should be used, as the chisel in breaking through the bridge may
traverse the antrum and enter the
facial canal, or the dislodged bone driven into the Canal. There is no
doubt but that, the facial nerve is frequently
injured during this procedure in the radical mastoid operation. The
prominence of the lateral or external semicircular canal is now
identified and immedliately
anterior to this structure, between it and the tympanic cavity lies the
prominence of the facial
canal. Occasionally, in this region the facial nerve will be found
exposed through at defect in
the canal wall.
1074
If
during the evacuation of the mastoid cells any suppurative process is
uncovered, it should be thoroughly
eradicated and the exposure and repair of the facial nerve postponed
until
the infection is entirely controlled. If it is deemed necessary to
drain the mastoid, the second
operation is not to be considered until the mastoid wound has been
completely healed for three
months and the ear free from all discharge, or sterile to culture.
The
stylomastoid foramen, having been exposed below, and the facial canal
located
anterior to the lateral semicircular canal, the operator may now
definitely orient the course of the
vertical segment, which follows a direct vertical
FIG. 205.- The sheath of the
facial nerve is
firmly attached to the periosteum of its canal; its attachment is
severed
with a cataract knife, while the nerve is gently lifted froii its bed.
In this region the facial nerve is very fragile and
gentleness is necessary to prevent tearing the nerve trunk. (Ney. The
Laryngoscope, 1922)
line between these
two points. The reduction of the posterior meant wall and mastoid cells
may now be safely conducted to the level of these points, without fear
of injuring the nerve. The vertical portion of the canal, which is
about 1 mm. in diameter, lies, in the average case,
about 3 mm. behind the posterior meatal wall; frequently the canal is
exposed as a ridge of
compact bone, through occasionally cells may open directly into it.
After the mastoid has been
reduced to about the level of the canal wall, the lateral or exposed
side of the canal wall, the
lateral or exposed side of the canal wall is carefully scaled off with
a small sharp chisel,
beginning at the stylomastoid foramen and progressing upward to the
bend of the canal.
1075
FIG. 206.– The nerve removed
from the facial
canal throughout its vertical and tympanic course. (Ney. The
Laryngoscope, 1922)
1076
Occasionally, the canal
is separated from the mastoid cells by 1 or 2 mm. Of solid bone; at
other
times it is only a thin shell.
The
vertical segment of the canal extends from the stylomastoid foramen to
the "bend'" or
the pyramidal segment, which lies in front of the lateral semicircular
canal and constitutes that
portion of the canal where its direction changes from the vertical to
the horizontal; the bend is
usually gradual, implicating from 2 to 6 mm. of the canal, though
occasionally the direction
changes
FIG. 207.- Decompression of
the facial nerve
by openinig its sheath. Diagrarn shows the attachment of the sheath of
the facial nerve to the
periosteum of the canal, which has been preserved in the dissection. The sheath of the facial
nerve is opened, exposing fibers which appear as a pearly white bundle. (Ney. The
Laryngoscope,
1922)
with a sharp angle. The
tympanic segment of the canal constitutes its horizontal portion, which
extends from the pyramidal segment to the genu and passes along the
roof of the tympanum; its
average length is about 8 mm. In its horizontal course, the canal
undergoes a gradual steady rise
in level, reaching the junction of the roof and inner wall, where it
leaves the tympanic cavity to form the genu. About
midway in its course it comes in close relationship with the fenestra
ovale
and stapes. After forming the genu, the canal gently curves toward the
cochlea and tunnels the
dense petrous portion of the bone throughout
1077
FIG.
208.- Plastic
procedure
to protect the
nerve from subsequent compression by turning down a flap of temporal
fascia which is passed under the nerve, separating it from immediate
contact with the bone; method of anchoring the
flap. (Ney. The Laryngoscope, 1922 )
1078
its course, independent
of the contour of the upper surface of the bone. This, the labyrinthine
section of the canial, extends from the genu to the lamini cribrosa.
After
the vertical segment of the facial nerve has been uncovered, the
operator, by the
same process of careful scaling, may uncover the nerve through its
pyramidal and tympanic
portions, the canal wall being gradually reduced until the nerve is
well exposed. In cutting away
the wall of the facial canal, fragments of bone will le found firmly
attached to the periosteum of
the canal and should be dissected rather than torn away; the sheath of
the facial nerve is
intimately attached to the peliosteum of the canal, and the tearing
away of attached fragments
may injure the nerve, which is extremely fragile. The separation of the
nerve from the canal wall
is begun at the stylomastoid foramen, where it is elevated on a fine
glass hook, and the
attachments of the periosteum to the bone are divided by a fine-pointed
cataract knife. During
dissection of the facial nerve, the operator should take time to
control oozing-a fine stream of warm saline is
usually effective.
With
the above mobilization of the nerve, the nature of the lesion will
probably be
apparent. If the nerve is not found to lie divided, it has probably
been subjected to compression
but careful inspection is required, as its ends may be united by sear
tissue. If it is completely
divided, it may be sutured, after the scar has been resected from its
ends, with arterial silk, care
being used to prevent torsion of the nerve trunk, the center of the
exposed quadrant of its sheath having been
previously marked by identification sutures. The needles used are
Lane's half-curved cleft-palate needles, No. 3, which are of very small
size and may be handled by mosquito
forceps. If the nerve is found to be the subject of compression, it
should be decompressed by
carefully splitting its sheath with a cataract knife, exposinge its
pearly white bundles; as the point
of compression is reached, these bundles are often pinkish in color.
If, in opening the sheath, an area of scar
invasion is met (in which the bundles lose their identity) this area
must be
resected and the nerve approximated by end-to-end suture. If
approximation is found diflicult,
because of a continuity defect in the nerve, the lower segment of the
nerve should be mobilized
as far forward in the parotid gland as possible. This mobilization, by
permitting the nerve to take
a more direct course, will frequently facilitate the correction of a
defect up to 1 mm. The
mobilization of the facial nerve may be somewhat increased by
uncovering its proximal end to
the genu of the canal, when it may be transposed; the anterior part of
the cartilaginous portion of
the external auditory meatus is separated from its bony wall and the
entire ear turned forward;
the nerve when sutured is made to pass anterior to the cartilaginous
portion of the meatal canal instead of assuming its
original posterior position. After transposing the facial nerve to the
anterior position, the cartilaginous canal is replaced and sutured. The
mobilization of the
proximal end of the nerve is greatly facilitated by reducing the
suprameatal wall, and removing
as far internally as necessary the superior surface of the petrous
portion of the temporal bone,
after elevating the dura until the genu of the canal is fully exposed.
When this procedure fails to overcome a continuity
defect, recourse may be had to grafting, when a sensory
1079
FIG. 209.- The portion of
the temporal
muscle denuded of its fascia, turned over the nerve. The facial nerve
now
lies between the flaps formed by the temporal fascia and the temporal
muscle. (Ney. The Laryngoscope, 1922)
1080
nerve of approximate
size may be inserted to fill the defect. It has not been found
necessary to
resort to a graft of this kind in any of the cases.
The
preparation of a bed for the repaired nerve is a rather difficult
procedure Occasionally the question may be solved by transposing the
nerve to a position anterior to the
cartilaginous meatus. In all decompressions and occasionally after
suture, the writer has
protected the nerve by turning down a flap of the temporal fascia and
muscle, the muscle being
used to cover the nerve, while the smooth surface of the temporal
fascia is passed under the nerve
to protect it from immediate contact with the bone.
The
incision is closed by interrupted sutures: three small rubber drains
will usually be
found sufficient to care for the rather abundant oozing following the
operation. These drains are
allowed to remain in place for 48 hours. A 5 percent dichloramine-T
solution is instilled into the
middle ear, and the external auditory meatus lightly packed with gauze.
If, during the course of
the operation, the ossicles have been completely removed, the external
auditory meatus mav be
obliterated by suturing together the cartilaginous canal before the
skin is closed. If this is done.
a drain is placed from the mastoid incision directly into the middle
ear, and the condition of the
wound carefully watched.
The
after-treatment consists mainly
FIG.
210.- Incision
closed; points of drainage indicated. External auditory meatus lightly
packed
with iodoform gauze. (Ney. The Laryngoscope,1922)
The after-treatment
consists mainly in preventing overstretching of the paralyzed facial
muscles
by the application of adhesive straps, as suggested by Yawger; or by
retracting the angle of the
mouth with a hook, the hook being held by a piece of string or tape,
which is tied to adhesive,
attached to a shaven portion of the scalp above the ear back of the
hair line, and kept under
sullicient tension to prevent overstretching of the paralyzed muscles
during laughter.
The
exposure anal repair of the facial nerve in the temporal bone is a
practical, though
very delicate, procedlure, and one requiring considerable patience.
Each step of the procedure
should be carefully and completely executed; a little carelessness here
or there may jeopardize
the entire operation. Before attempting this procedure clinically, the
operator should thoroughly
familiarize himself with the anatomy by making several complete facial
nerve exposures in the dissecting room.
It is not necessary to use any especially made instruments in this
operation; it is essential, however, that the surgeon be equipped with
the smallest size chisels,
gouges, and osteotomes.
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