214
SECTION I
GENERAL SURGERY
CHAPTER VIII
LOCALIZATION
AND EXTRACTION OF FOREIGN BODIES UNDER X-RAY
CONTROL
LOCALIZATION
EARLY HISTORY AND LITERATURE
In
reviewing the methods of localizing foreign bodies, one is immediately
impressed with
the fact that the publications of the year 1896 set forth the
principles at the foundation of most of
the localizing methods of today. This year saw the publication of
Buguet and Gascar,1 setting
forth the classical formula:
Depth
equals FORMULA when a represents the distance the tube
is shifted: b the distance
of shift of the
shadow of the projectile; and h the height of the screen or plate from
the focus of the tube. Early in
this same year Thompson,2 in America, and Imbert and
Bertin,3 in France, proposed stereoscopy
in connection with X-ray localization. The method of making two
exposures at right angles, the
so-called method of right-angled planes, was proposed by White,
Goodspeed, and Leonard.4
The following
year marked the publication of Mackenzie Davidson and Hedley,5 on the
triangulation method, visualizing in space the position of the foreign
body by means of crossed
threads, and the method of Gerard 6 and Levy-Dorn7 which utilized the same principle of
triangulation, but without the cross-thread visualization. Stechow
wrote further on the method of
making two exposures at right angles.8 Exner described a
method combining a ring localizer with
the triangulation principle, and later used the parallax principle.9 The parallax principle was also
used by Levy-Dorn.7 Rémy and Contremoulins10 described an elaborate apparatus which was
apparently the forerunner of the Hertz compass as used today.
In
1898, in addition to other methods, Marize used four small adhesive
disks of lead;11 two
be placed at the points on the skin where the vertical ray passing
through the foreign body entered
and left the part; the other two were placed in a similar manner at
right angles (or nearly so) to the
plane of the first two. The intersection of the two diameters joining
these four points gives the
location of the foreign body.
Galeazzi 12 was apparently the first to
publish description of the
“pierced screen” the ordinary
fluoroscopic screen with a small hole drilled through it and the lead
glass cover, sufficiently large
for the insertion of a small rod for estimating the depth from the
screen surface to the skin in those
locations where it was not possible to bring the screen in actual
contact with the part understudy.
He also employed the triangulation method with single tube shift, and
added a direct-reading scale,
obviating the necessity of calculations.
215
Sechehaye,13 in January of this year, published a review of
the
literature on the subject and
was able to summarize 32 methods and authors.
The
writer, in 1918, published a brief history of the development of
foreign body
localization by means of the X rays, with a bibliography containing
more than 200 references.14
The
more than 200 methods referred to in this review were really
susceptible of
classification under a few of the methods described in the first two
years of the roentgen era. Few
of the methods later published were anything more than rediscoveries or
minor modifications of
essential principles already discussed and used.
The
Hertz compass, though first used in 1907, was not referred to in
literature until 1914.15 Telephone probes and other localizers working on the magnet principle
were innovations appearing
shortly before the opening of hostilities in 1914.16 The
most complete work on the subject of
foreign body localization was written by Ombredanne and Ledoux-Lebardc.17 Delherm and
Rousset,18 and Nogier 19 also wrote
booklets on the subject.
The
United States Army X-ray Manual was finally adopted as the working
manual of the
United States Army Medical Department, and in it a large section was
given over to localizations.20 An effort was made to select the more valuable methods and to
standardize the necessary
instruments and the technique for their operation under the methods
selected. It was exceedingly difficult for those who had not actually
participated in forward area surgery under battle conditions
to realize how simple, direct, and quick the localizing methods had to
be. It was soon recognized
that any method involving the use of plate or film records was
unsuitable because of the time and
labor necessary to make the localization, and it soon transpired that
the medical officers actually doing localization work in forward
hospitals exhibited a marked tendency to employ very simple
methods capable of being used without accessory instruments other than
the fluoroscopic apparatus
itself.
METHODS
Though civil surgery affords relatively infrequent
opportunity
for the surgeon or the
radiologist to put to actual test the methods of localization which are
to be found in every textbook
on radiology, the World War afforded an extraordinary multiplicity of
occasions for studying
foreign body cases, and enforced a careful analysis and modification of
the more than 200
procedures which were described in the medical press early in the war.
Some
of the procedures described are complex, some are simple; some require
complicated
apparatus or special instruments, while others may be carried out with
any of the ordinary types of
X-ray equipment; some required the aid of radiographic plates, while
others are screen methods
quickly performed and affording an instant answer to the surgeon's
query as to the presence or
situation of the offending foreign substance. Out of the war have
arisen systematized localizing
procedures, with standardized apparatus especially adapted to the
expeditious handling of large
numbers of wounded men. Some of the standardized types of apparatus
developed for military
work are already being used in our civil hospitals, and the general
trend of manufacture
216
of X-ray equipment is
toward the simpler instruments developed during the war.
It
is the purpose to set forth briefly herein only those methods most
readily learned and
carried out with a minimum of accessory instruments. Explanations of
geometrical propositions, for
lack of space, are reduced to a minimum. Any reader interested in the
details of such mathematical
propositions will find discussions in the various excellent treatises
on localization which have been prepared by the medical departments of
the various allied armies, already referred to.
Magnets,
vibrators, and telephone probes have been variously recommended by
military
surgeons but they are limited in their usefulness. Magnets, for
instance, are applicable only to the
localization and extraction of such metallic foreign bodies as are
responsive to magnetic attraction,
whereas the radiologic method should discover all metallic foreign
bodies (with the possible
exception of aluminum), besides many nonmetallic substances. The
radiologic method as a part of
the surgical procedure lends itself admirably to helping the surgeon
during the extraction of any
foreign body, whereas the magnet and vibrator methods above referred to
have the same
limitations in respect to nonmagnetizable substances.
The
person undertaking a localization should not confine himself to an
estimation of the
depth of the foreign body, but should acquire all possible information
afforded by an X-ray study of
the case. For the best results it is essential that the radiologic work
be done by a physician, or,
better still, the surgeon should be familiar with the radiologic
procedures involved in foreign body
localization; indeed, there is such temptation for the surgeon himself
to go ahead with the
radiologic part of the extraction procedures that unless he has a
thorough technical knowledge of
the subject he is likely to harm himself through inadvertent
overexposure to the rays. These dangers
will not be discussed here as they are fully described in numerous
textbooks.
Localizations
are usually accomplished by fluoroscopic methods, although there is no
objection to radiographic methods other than that they involve more
time and expense and are not
so informing as the screen methods. Stereoscopic radiograms are more
valuable than single plates.
A localization
should afford the following information: (1) Anatomical data, showing
the
relation of the foreign body to neighboring structures, such as a
trochanter, a condyle, or some other
well-known bony point, to a muscle; or to an artificial opaque marker
affixed to the skin. The
condition of any injured hones should be carefully recorded. (2)
Mathematical data as to the depth
of the foreign body in relation to marks or markers on the skin. (3)
Directions which will guide the
surgeon to the foreign body. This guidance is
frequently afforded by the fluoroscope through observations made during
the removal of the foreign body.
The following
localizing methods are considered herein: (1)
Rotation of the part; study of the movements of the shadows of the
projectile or other foreign body
in relation to neighboring opaque structures or skin markers. (2) The
“nearest point" method. (3)
The parallax method, which is often combined with the nearest point
method. (4) The
orthodiagraphic method, which is
217
also often combined with
the nearest point method. (5) The method of right-angled planes
(four-point survey). (6) The multiple diameters method.(7) The
single-shift triangulation method, with
which may be included the stereoscopic method. (8) The double-shift
fixed-angle methods. (9) Harpooning methods, combined with
reconstruction of the part by the aid of a cross-section anatomical
atlas.
There
are numerous other methods which might be described, but these
mentioned above
are all very simple, easily learned, quickly performed, and accurate to
within a half centimeter,
without the aid of plates. There is no reason why one or more
radiograms of the part should not be
made if the surgeon so desires, especially if he has not been present
at the X-ray localization. If
such plates are made, they should be stereoscopic plates.
APPARATUS REQUIRED
In
addition to the usual current-generating apparatus of any type
supplying at milliampere or
more, a tube of sufficient hardness and a horizontal a or vertical
fluoroscope installed in a room
capable of being completely darkened, the following items of equipment
are necessary: A ruler; a localizing rod or wooden stick the size and
length of an ordinary lead pencil, with a metal
ring, approximately 2 cm. in diameter, screwed into one end, and an
ordinary screw with a
FIG.
109.- Palpator
made
from a small wooden rod, with a screw and a screw eye
well-rounded head in the
other; grease pencils, such as are used for marking on glass or
chinaware;
suitable skin-marking ink; an aniline dye may be used, or the Finzi
ink; b a cross-section anatomy,
that published for Professor Symington, being highly satisfactory.21
The
foregoing accessory articles permit the performance of most of the
localizing procedures listed and described in this article, but the
following inexpensive and simple
accessories are often very useful: Large calipers, such as obstetrical
calipers; a foot-switch for
controlling the current through the X-ray tube; better still, a
combination switch, controlling both the overhead light and the tube
current; strips of flexible metal, such as composition tin, 1.5
a It
is assumed
that the majority of the work will be done with the standard X-ray
table by
fluoroscopic methods and with the tube below the table. The tube box is
movable in two directions,
as in the usual trochoscope, and is provided with a double shutter
giving a diamond-shaped opening
with the diagonals parallel and perpendicular to the length of the
table and also with an adjustable
slit, under separate control, parallel to the length of the table. The
tube box runs freely and may be
locked in any position against both lateral and longitudinal movement,
and is also provided with a
simple means for fixing the amount of tube shift for a particular
purpose or for measuring any shift
from a fixed position.
The
fluoroscopic screen is carried by a ball-bearing carriage mounted on
the table rails, and
provision is made for a movement parallel to the table, for rotation
about a vertical axis and also
for a vertical shift. Each of these movements may be prevented by a
suitable, convenient lock. The
fluoroscopic screens are perforated with a small hole through which a
marking device may be
inserted to mark the skin in the vertical ray. When this ray is spoken
of it is assumed that the table
will be substantially in a horizontal position and that a line joining
the target with the center of the
diaphragm will be perpendicular to the plane in which the tube may
move. The opening in the
screen also serves a very convenient purpose in temporarily fixing in
position the scales and other
pieces of apparatus which it is desired to use on the fluoroscopic
screen.
bThe
writer prefers an ordinary indelible pencil which makes a
semipermanent mark on the
moistened skin. For war surgery the indelible pencil would hardly
satisfy the need, but in civil
practice it will usually do very well.
218
or 2 cm. in width, and
of appropriate lengths for surrounding an arm, a leg, or the torso, and
hinged
together in pairs; a cannula and trocar, and a supply of fine piano
wire cut into lengths somewhat
longer than the trocar.
CENTERING THE TUBE
Accuracy
in localization work requires an exactly centered X-ray tube. Some of
the French
manufacturers supply a special device for centering the tube. Among the
numerous groups of rays
given off in the active hemisphere of an X-ray tube is one to which the
term "normal ray" has been
applied. It will be recalled that in geometry a line normal to a second
line is one perpendicular to it,
making with it two right angles. In radiology, therefore, the term
FIG. 110.- Showing the positions of shadow of plumb
bob on
fluorescent screen when X-ray tube is
properly centered, and when off center
normal ray is applied to that group of rays perpendicular to
the long axis of the tube. Unless the tube is carefully centered
beneath the diaphragm in such a way
that when the diaphragm is closed down to a small opening the normal
ray will pass through it,
there will be a resulting error in the localization calculations.
One
may determine when the tube is centered by the following means: When
the military
type of table is not available, the screen is locked in position above
the tube box and a plumb bob
attached to a metal marker, such as a lead ball, is affixed by adhesive
plaster to the underside of the
screen somewhere near its center (fig. 110). The opening in the
diaphragm is reduced to about 1
cm. and the tube box moved until the pencil of rays emitted through the
small opening casts the
shadow of the plumb bob and the metal marker on
219
the screen. If the two
shadows do not coincide, the tube is not correctly centered, and
alterations in
its position should be made and compared until the two shadows
coincide.
An
ordinary tin cup or a glass tumbler may be placed accurately over the
small opening in
the diaphragm, care being taken to see that the cup or tumbler is on a
level support, and that the
opening in the diaphragm comes as near as possible to the center of the
cup. Then the diaphragm is
opened so that the shadow of the whole cup shows. One may judge by the
symmetry of this shadow
whether or not the tube is properly centered (fig. 111).
With
the table supplied by the United States Government during the war, the
diamond-shaped opening of the shutter is reduced to about 1 cm. The
tube box is locked in position and the
screen moved so that the perforation in its center will coincide with
the center of the projection of
the small
FIG. 111.- Screen
appearance of a tumbler with the tube
properly centered
and not properly centered
diagonal opening of the
shutter. The carrier is locked against longitudinal motion and against
rotation, and the screen raised by the vertical movement of the
carrier. If the perforation does not
retain its symmetrical position the tube needs shifting until this
condition obtains.
It
is important that this process of centering the tube be carried out
each time a localization
is attempted, unless a number of localizations are planned for the same
day.
MARKING THE SKIN
For
marking the skin in relation to foreign bodies, especially where there
is only occasional
need for localization work, the ordinary indelible pencil, dipped in
water or used on the moistened
skin, is quite satisfactory. This mark is not obliterated by painting
the skin with tincture of iodine. If
a black mark is desired, which dries quickly and which will withstand
scrubbing, the Finzi formula
is useful: Pyrogallic acid, 1 gm.; acetone, 10 c.c.; liquid chloride
of iron, 4 c.c.; wood alcohol q. s.
ad., 20 c.c.
This
ink, when made up fresh about once in 10 days, makes a black mark and
dries quickly.
It is best applied with a sharp stick or a fine brush. If allowed to
dry thoroughly the mark will resist
alcohol, show through an iodine stain, and persist from two to seven
days.
220
In
emergency cases a persisting mark can be made with a stick of silver
nitrate on the skin
moistened with a few drops of photographic developer. A match or
toothpick dipped in a 10 or 20
percent solution of silver nitrate will serve the same purpose without
the irritation of the skin
which sometimes results from the use of the silver nitrate stick. An
aqueous solution of brilliant green has also been suggested for marking
the skin.
The
method of marking will vary with the case. If multiple foreign bodies
are present, it is
sufficient to mark such of them as can be located by the " nearest
point" method with a dot
surrounded by a circle, the dot indicating the nearest point. In cases
of a single foreign body it is
well to make as many marks as may be helpful to the surgeon; for
instance, one mark
perpendicularly over the foreign body recording its depth, with two
horizontal marks on either side
of the part in the plane in which the foreign body lies.
It
is also highly important that the localization be carried out and the
marks placed upon the
skin in the position which the patient is likely to occupy while
undergoing operation. Hence, when
it is feasible, the surgeon or his assistant should be consulted as to
the probable method and site of
surgical approach. It should be stated as an axiom that in all
localization work the patient should
be carefully placed in the operative position before one begins to make
the localizing marks.
TECHNIQUE
One
of the first steps in the localization of a foreign body, after
determining its presence, is
an estimation of its approximate position--whether it lies in front of
or behind a certain bone or other
anatomical landmark, whether it lies within the substances of a great
muscle, etc. This is termed the
anatomical localization, and it often suffices to enable the surgeon to
perform the extraction.
Extraction
of the foreign body is often one of the lesser considerations in
dealing with a
gunshot or other emergency case. The proper toilet of the wound, the
removal of clothing and other
foreign materials which may be carried into the part by the projectile
or foreign body, as well as
attention to damaged bone, nerve, or other tissue, are of paramount
importance, and in many
instances the extraction of the offending foreign body comes in for
secondary consideration. Along
with the data for localization the radiologist should supply all
information possible regarding injury
to bone, dislocations, blood or pus accumulations, gas infections, and
other conditions relating to
the wound.
ANATOMICAL LOCALIZATION
From
the surgical standpoint, it may be stated that it is more important for
the surgeon to be
informed of the anatomical situation of a foreign body than of the
mathematical distance it lies
perpendicularly below a given point on the skin. For example, the
surgeon is more interested in
knowing that a foreign body has penetrated the pleura than that it lies
4.5 cm. below a certain point
on the back when the patient is lying prone; and whether a projectile
recorded as being 7 cm.
beneath a point just below the vertebra prominens is intrapleural or
lies within the substance of the
body of the last cervical or the first dorsal vertebra. In order to
give this information it is essential
that the
221
radiologist should
possess an accurate knowledge of anatomy. It is here that the
cross-section
anatomies may lend considerable aid, though sometimes anatomical
conditions vary in individual
cases on account of unusual accumulations of fat and because of varying
build in different
individuals.
The
anatomical location can often be determined by requiring the patient to
carry out some
active movements, or the radiologist can himself move the part and
observe the changing relations
of the foreign body during these maneuvers. The movements of the shadow
during the contraction
of muscular masses are significant. For instance, a foreign body in the
forearm which exhibits considerable displacement when the patient
closes his fist manifestly lies in one of the flexor
muscles; if it ascends on flexion of the thumb and remains stationary
during movements of the
other fingers, it obviously lies in the flexor muscle of the thumb.
Foreign
bodies in the region of the eye may be more exactly localized by
causing the patient
to open and close the eyes, to rotate the eyeball, and to carry out
other movements which bring into
play the individual eye muscles. A method of localization of foreign
bodies in the eye will be
considered later in this discussion. By having the patient protrude the
tongue, open and shut the
mouth, perform movements of deglutition, swallow a capsule containing
bismuth, etc., one is able
to determine the relative anatomical position of a foreign body in the
face or neck.
For
differentiation between intra-and extra-thoracic foreign bodies, it is
usually sufficient to
cause the patient to practice several deep inhalations and exhalations.
During inspiration the lung is
displaced from above downward, while the thoracic cage is displaced in
a contrary sense. Lateral
or oblique fluoroscopy of the chest is very important, especially when
the patient's diaphragm is
immovable. Unless rather definite and extensive movement of a foreign
body in the lower half of
the chest can be determined during respiratory movements (save when the
diaphragm is
motionless), it should not be considered to be intrapulmonary: in the
upper part of the thorax
intrapulmonary foreign bodies may exhibit very little respiratory
movement, and in the middle of the lung on either side they may be
quite stationary. As intrapulmonary and hilus calcifications
have caused many errors in the study of intrathoracic foreign bodies,
it is well to have stereoscopic
plates made in all doubtful cases. The pulsation imparted to
intrathoracic foreign bodies by the
heart or great vessels, especially to those lying near the midline, may
occasionally cause great difficulty in exact localization.
Foreign
bodies lying within the pericardium are usually movable and gravitate
to the most
dependent point possible when the patient changes his position; in old
cases, intrapericardial
foreign bodies may be attached to the wall of the pericardium and
render the diagnosis more
difficult.
Projectiles
lying near the diaphragm, but just above it, should be easily
localized, provided
one views the patient from a sufficient number of angles.
Intraabdominal, subdiaphragmatic foreign
bodies are not so easily localized, Stein and Stewart 22 have recommended the introduction of
oxygen or some other gas into the peritoneal cavity, so that by
changing the posture of the patient it is possible to separate the
subdiaphragmatic structures from the
222
diaphragm itself. Many
cases of wounds with intraabdominal projectiles will have developed
sufficient gas in the peritoneal cavity to make the introduction of
oxygen unnecessary. Careful
palpation of the abdomen, inflation of the colon or stomach in selected
cases, the use of the
Trendelenburg position, etc., will usually be sufficient without an
induced pneumoperitoneum.
Viallet and Tanton23 have called attention to the
possibility in certain cases, especially in wounds
of the urinary bladder, of localizing a foreign body inside a hollow
organ if, by localizing
alternately from the anterior and the posterior aspect of the torso,
results are obtained which
disagree as regards the total thickness of the subject and are notably
less. This is due to the
displacement of the projectile from one position to the other.
In
considering foreign bodies in relation to the vertebral column,
attention should be drawn
to the great value of stereoscopic plates and to lateral radioscopy
FIG.
112.- Screen appearance of an intracranial foreign body
and radiography of the
spine, too little practiced by the average radiologist. Lateral
radiography of the spine is generally
considered impossible without extraordinary apparatus; on the contrary,
the average type of
portable apparatus will suffice to make excellent radiograms if
intensifying screens are used. Even
the sacrum can be radiographed laterally in this manner.
Foreign
bodies in the pelvis should be localized with ease provided one makes
stereoscopic
radiograms. In occasional cases it may be possible to gain more
information concerning a foreign
body located in or near the rectum if an assistant makes intrarectal
manipulations at the moment of
the X-ray examination.
In
wounds of the head it is sometimes possible for the casual X-ray
observation to be very
misleading. This is demonstrated in Figures 112 and 113.In Figure 112 a
typical intracranial
projectile is shown in the frontal and lateral
223
projection. Figure 113
represents the actual position of a projectile which is extracranial
and lies
within the soft tissues of the temporal region, but which with the
usual frontal and lateral X-ray
projection appears to be intracranial. This error would hardly occur
during a fluoroscopic
localization, but it would been entirely possible with a radiographic
procedure and the possibility
should be duly noted.
FIG.
113- Screen appearance which might
lead
to an erroneous diagnosis of intracranial foreign body.
In
a routine examination the patient is first placed on the horizontal
fluoroscope and a brief
fluoroscopic survey made to determine the presence of a foreign body.
Of course, one may deal
with foreign particles too small to be seen with the fluoroscopic
screen, but except in the eve and a
few other similar critical locations, a metallic foreign body too small
to be seen with the fluoroscope
224
usually does not require extraction. When the eyes are properly
prepared by a preliminary
stay in a darkened room one may see on the screen the shadow of such
small substances as a
common pin or a bird shot in the cecum or a fairly small foreign body
in the eye. In civil practice
one or more radiograms will be made in nearly every foreign body case.
In France more than 5,000
wounded men passed through the X-ray department of a certain unit
without a single plate being
made, all the localizations being done by the screen method.
ROTATION OF THE PART
The presence and general locality of the foreign
body having
been determined, it is easy by
rotation of the member or part to determine the relative depth of the
foreign body in relation to
bony landmarks or other opaque structures or markers. The shadows which
move in the direction
in which the part is rotated (figs. 114 and 115) will be found to lie
between the axis of rotation of
the part and the fluorescent screen; in other words, nearest the screen
or nearest the upper surface of
the part. On the other hand, if the shadow of the foreign body is
displaced in the opposite direction
to that in which the part is rotated, the foreign body will be found to
lie between the axis of rotation
of the part and the tube; in other words, nearest the inferior surface
of the part or member. This is
illustrated in Figure 114 (after Nogier) where projectile P1 is located near the
upper surface, and P 2 near the lower surface of the limb. When the part is rotated to
the right, in the direction of the
arrow a, naturally the shadow of projectile P1 toward
the left. P1 therefore lies
above the axis of
rotation of the part and P 2 between the axis of rotation
of the part and the tube.
FIG.114.- Method
of rotation of the part.
(Nogier)
NEAREST-POINT METHOD
After
the above-described method of rotation has enabled one to form an
opinion as to the
general situation of the projectile, the next step is to palpate the
part containing the projectile and at
the same time to observe on the screen the results of the palpation.
One will not employ the
unprotected fingers for the purpose, but rather the localizing rod
(fig. 109) or any suitable pointer.
By the movements of the foreign body under pressure upon the soft
tissues surrounding
225
it and by the
amount of pressure required, one may estimate very accurately the point
upon the skin which is nearest to the foreign body, and by simultaneous
rotation of the part the
depth at which the foreign body lies. In utilizing the palpating rod,
one should turn the part until the
position is found in which the shadow of the projectile or foreign body
will be as near as possible to the surface. This done, the part is
explored by touching it with the extremity of the palpating rod
while making light vibrating movements. The nearer the end of the
palpator to the " nearest point "
the more will the foreign body move with these slow vibrating
movements. When the movements transmitted by the palpator show the
maximum mobility of the foreign body, this point on the skin
should be marked as indicating the shortest possible distance from the
foreign body to the skin.
This
method is, of course, best adapted to the foreign bodies which are
relatively superficial,
as in the soft tissues of the arms, legs, neck, axilla, and buttocks;
but it is a fact that fully one-half
the foreign bodies may be included
FIG. 115.-
Method
of rotation of the part
in this class. It is
also frequently of value in demonstrating that a foreign body is within
a joint, or
that a foreign body can not be displaced by pressure, suggesting that
it may be embedded in very
firm deep tissue or in bones.
The
nearest point having been marked, the depth of the foreign body is next
determined by
one of the following methods.
PARALLAX METHOD
This
method is based upon the experimental fact that two opaque markers
placed at an equal
distance from the screen will, when the tube is moved, cast upon the
screen two shadows whose
range of movement is equal; that is, whatever may be the displacement
of the tube, objects lying in
a plane parallel to the screen will project their shadow upon the
screen in parallel lines. In Figure
116, for instance, T1 and T 2 represent
two positions of the tube; P,
the projectile; L, the
palpating
rod held against the part at the same level as the projectile; P1 and P 2, the shadows of the
projectile
with the tube at T 1 and T 2,
respectively; and L1 and L 2, the
shadows on the screen of the end of
the palpating rod under the same circumstances. The line L1 and L2 represents the
excursion of the
226
FIG.
116.– Diagrammatic representation of the parallax method.
shadow of the palpator
as the tube is moved back and forth from T1 to T 2;
and the line P 1 P2, the
excursion of the shadow of the projectile P. It is obvious that when
the
foreign body P and the end of
the palpating rod L are at an equal distance from the tube, the
excursion of their respective
shadows will be equal and the lines L1 L2 and
P1 P 2 will be equal. When
the foreign body is nearer
the tube than the palpating rod, the excursion of the shadow of the
foreign body will be greater than
that of the shadow of the palpator; on the contrary, when the palpator
is in a plane nearer the tube,
the excursion of its shadow will be greater than the excursion of the
shadow of the foreign body.
This
maneuver is carried out as follows: The end of the palpating rod is
placed against the
part as near as possible to the foreign body and in what
FIG. 117.- Screen
appearance during different steps of the parallax method
227
seems to be the plane of
the foreign body, and both shadows are brought to the edge of the
shadow
of the opened diaphragm. The tube is then deliberately moved in such a
way as to cause the
shadows to travel to the other edge of the open diaphragm. In Figure
117, a, the foreign body
shadow lags behind the shadow of the palpator in reaching the mark,
therefore the palpator is in a
plane deeper than that of the projectile. If one raises the palpator
slightly in order to correct the
error (fig. 117, b) and moves
the tube just enough to bring both
shadows again to the edge of the
diaphragm, the tube is shifted in the contrary direction, causing the
two shadows to return to the
first position. This time the shadow of the projectile travels faster
than the palpator, and it is
evident that the position of the palpator was overcorrected and brought
nearer the surface than the
foreign body. Once more a correction is made, as shown in Figure 9, c,
and now, when the tube is shifted, both shadows arrive at the other
edge of the diaphragm simultaneously. The
screen is then removed and a horizontal mark placed upon the skin at
the level of the palpator
point. From this it is easy to deduce the distance at which the foreign
body lies from the surface of the part. The procedure may be repeated
on the other side of the part if it be an arm, leg, head, or
neck.
FIG. 118.- Schematic drawing of parallax
localizer. V,
Upright; R, ring; B, ball; P, foreign body; C, opening in base
This
method is also valuable in connection with fluoroscopic screen control
of foreign body
extractions carried out during operation, for it permits the
radiologist to tell the surgeon whether the
end of the seizing forceps lying in the wound is above or below the
foreign body to be extracted.
Figure
118 is a schematic drawing showing the parallax localizer provided for
the United
States Army Medical Department. Figure 119 is a photograph of the
apparatus itself.
FIG. 119.- Apparatus shown in
Figure 118
228
ORTHODIAGRAPHIC METHOD
Another
simple means of ascertaining the exact distance from the foreign body
to the
nearest point on the skin is the orthodiagraphic method (fig. 120). The
part is rotated until the
shadow of the foreign body P
and the marker upon the nearest point P1 lie in the same
plane. With
the part held in this position, the tube is shifted until the shadow of
the foreign body lies in the
middle of the illuminated field upon the screen. The diaphragm is then
narrowed down to the
smallest possible opening which will illuminate a field upon the screen
larger than the foreign
body, the screen being held in a horizontal position parallel to the
table and perpendicular to the
central ray. The shadow of the foreign body is then brought to the
center of the small illuminated
field upon the screen at a and a mark made upon the screen at
this point with a grease pencil. The
screen being held rigidly still, the tube is shifted until the small
illuminated field shows as its
center the marker upon the skin at a1.
The
distance aa l is equivalent to the distance PP 1,
the depth of the
foreign body from the
nearest point upon the skin.
METHOD OF
RIGHT-ANGLED PLANES
Another
simple method of localizing the foreign body is the four-point survey
or the method
of right-angled planes (fig. 121). This method is applicable only to
those parts which can be rotated,
unless a special instrument for fluoroscopy in both the vertical and
lateral position is available.
Special apparatus has been designed for simultaneous fluoroscopy of a
part in two directions at
right angles to each other.
We
first pass the normal ray through the projectile P in the direction aa l, and by means of
the ring marker the point of exit and the point of entry of the
vertical ray are marked on the skin
(fig. 122). The part is then rotated through approximately 90º, when
for a second time the normal
ray is made to passthrough the projectile, now in the direction bb 1,
and these two points again
ascertained by means of the ring marker and indicated upon the skin. The
FIG. 120.- Orthodiagraphic
method of
localization
FIG. 121.- Measurement in
two directions
(right angled planes)
229
localization of the
foreign body is thus definitely determined at the crossing of the two
axes, and
with the aid of a cross-section anatomical atlas one may reconstruct
the part and the position of the
foreign body. One may rotate the tube instead of the part if the
apparatus permits it. It is not
essential that the two planes of observation be at right angles; the
crossing of any two axes through
the foreign body will indicate its position.
This
method is slightly less accurate than the multiple diameters or
six-point survey.
MULTIPLE DIAMETERS METHOD
The
multiple diameters method consist simply in securing several lines of
sight through the
body, each of which is made to pass through the projectile. The point
of entry and the point of exit of the normal rays used in establishing
these lines are plainly marked upon the skin. It is, of
course, essential that a small diaphgram opening be employed in these
methods.
FIG. 122.- Screen appearance of, and method of
using, the ring localizer
FIG. 123.- Malleable
band, and the six-point
survey methods
The
method of multiple diameters combined with the use of the strips of
malleable metal,
as employed by several authors, was as follows: 20
Two
pieces of flexible metal, such as a composition of tin, are hinged
together in the
middle and placed around the body in the plane of the skin marks and
made to conform to the
shape of the body. Note is made of the distance that one unhinged end
overlaps the other, and the
skin marks are transferred to this metal band. After carefully removing
the latter from the body, it
may be laid down on a card or a sheet of paper, and by bringing the
overlapping end to its original
position a pencil tracing will show the outline of the body in the
plane of examination. The skin
mark positions are then transferred to the diagram so as to make an
approximate duplicate of the
shape of the body and the location of the external skin markings.
If,
on this diagram (fig. 123), one numbers the skin marks in series, 1, 2,
3, 4, 5, and 6, and
joins 1 and 4, 2 and 5, and 3 and 6, and if the work has been
230
strictly accurate--that
is, if the sight lines were properly established-if the shape of the
body did not
alter by change of position when the band was puton, if the band was
properly formed and not
distorted afterwards these three lines will intersect at a point; as a
rule they are likely to form a
small triangle, but with an excellent chance of the projectile being
located in this small area. If one
now compares the diagram, so formed, with a cross section anatomy for
the same region of the
body, definite anatomical information as to the position of the
projectile and the relative position of
muscles or organs likely to been countered in its removal is gained.
The
value of this method will depend to a considerable extent upon the care
exercised in
forming and handling the strip and in properly adjusting it to the
cross section anatomy. It is
suggested that in many cases at least one of the skin marks might well
have a definite relation to
some anatomical landmark, so that there could be little opportunity for
a rotation of the band with
reference to the anatomical chart. This will be especially true of
portions where the cross section is
nearly a circle. It should also be observed that the accuracy of this
method increases when the three
sight lines are made to differ materially in direction. In some cases,
this would be a difficult matter,
as with a seriously wounded patient, or one for whom change of position
on the X-ray table would
be painful.
Lacking
malleable metal strips one may make a cardboard cutout conforming to
the contour
of the part, and transfer to this cutout the skin marks indicating the
points of entry and exit of the
lines of sight above referred to. This cardboard is not, however, so
easily sterilized and taken into
the operating room as a guide for the surgeon.
SINGLE-SHIFT TRIANGULATION METHOD
One
of the earliest procedures of foreign body localization, as noted
above, was that set
forth in 1896 by Buguet and Gascar 1 who applied to foreign
body localization the classical
formula, depth= bh/a+b where a represents the distance
the tube is shifted; b the distance of the shift
of the foreign body shadow; and h the height of the screen or
plate from the point of focus of the
tube.
The
patient is placed upon the couch in the position he will occupy during
operation and the
screen fixed horizontally above the part and resting on it. The tube is
moved about until the foreign
body shadow lies in the normal ray, and a mark is placed on the skin at
the points of entry and exit
of the normal ray. The position of the projectile is further marked
upon the lead glass of the fixed
screen. On opening the diaphragm the tube is shifted any distance,
say10 cm., without disturbing
the position of the patient or screen, and the new position of the
shadow of the foreign body is
marked upon the screen. By measuring the height h from the screen to
the point of focus of the
tube, the distance a the tube
is shifted, and the distance b the shadow of the foreign body was
moved, we are able to work out the formula above stated and to arrive
at the depth of the foreign
body below the screen. In order to determine the exact depth below the
skin, it remains only to
subtract the distance from the screen to the skin, if the skin and the
screen are not in contact. This
method
231
may be worked out
accurately without arithmetical computation by simply redrawing the
procedure
to scale.
In
civil practice, where only the occasional localization case is
encountered, there is no
necessity for maintaining a fixed distance between the screen and the
focus point, for all these
distances and shifts can be easily measured. In war, it will be better
to adopt a standard focus-screen distance h (55 or 60 cm.) and a
standard tube shift a (10
cm.), and to construct tables by
which the depth of the foreign body below the screen can be instantly
read from the shadow shift.
Many such tables and many graphic devices were published during the
war. The device intended
for use by medical officers of the United States Army during the late
war is illustrated in Figures
125 and 126. For use of this apparatus it is
FIG. 124.- Classical
single-shift triangulation method
better to employ: (1) A
fixed tube shift of 10 or 15 cm. may be used or tin image shift of an
exact
number of centimeters. (2) A fixed target-screen distance may be used.
This is not, however,
always convenient. (3) The exact setup of Figure 124 may be reproduced
by use of a device shown
in Figure 125, which may be supplied in case of a desire to use this
method.
This
device consists of two straight bars, A and B, at right angles to each
other. B carries an
adjustable slider, R. A carries two sliders, E and G. E is not moved
after one adjustment unless a
new table is used. The slider, G, has notches, 0, 1, 2, etc., 1 cm.
apart, and a slider, P, with a latch
engaging these notches. A scale, S, with its zero point at the upper
end is carried by G. A lug at H is
in line with the zero of G. If, now, DH-tube shift, GH-target-screen
distance, P1O-image shift, then a
straight line, P1D will cross the scale, S, at the depth of
the foreign
body below the screen. The
instrument should
232
be fastened to the wall
in a convenient place and the measurements needed should be made by a
caliper, thus avoiding any reading of scales except the final depth.
If
in the particular case illustrated, the image shift is 4 cm. and the
zero point of scale, S, is
set above H an amount equal to
the target-screen distance, and DH
is the tube shift for an image
shift of 4 cm., a string drawn as indicated will cross the scale at a
point is the depth sought.
When using the
standard table the slider, E,
is adjusted so that a length measured on the
screen-carrier support will show how much above E we must place G in
order that GH may
represent the target-screen distance.
It
will be observed that this instrument serves to reproduce tube and
image positions as actually observed by the roentgenologist; i. e., one
vertical ray in which the skin is marked, and one oblique ray whose
intersection with the former corresponds to the distance of the
projectile from the screen.
An
accessory device is also supplied, consisting of a strip of celluloid
with a pin centering
in the perforation of the screen, and having centimeter divisions
clearly marked both ways from the
center, making it quite easy to secure an exact number of centimeters
displacement.
There is a
considerable advantage in making the distance the image is shifted a
definite number of centimeters, and measuring the tube shift method.,
also during the tube shift, since the showing method of using
adjustable double-slider caliper relative error in measuring the small
length of image shift is greater than that in measuring the long tube
shift.
When
supplied with the accessories indicated above, this method becomes as
expeditious as
others, and is as accurate as any of the depth methods.
In
the single-tube shift method there are various procedures which maybe
used. They all
require essentially the same data, namely, (1) tube shift,
233
(2) image shift, (3)
target-screen distance. If these distances are measured to scale in
centimeters, it
is possible to compute the end result.
The
apparatus supplied for this method includes a scale whereby a definite
image shift may
be made, if that is desired by the operator. There is also a provision
for a definite tube shift of either
10 or 15 cm. on the standard table and for the measurement of any tube
shift, if the operator desires
to make the shift of the image a definite amount-the procedure
generally advised.
FIG. 126.- Apparatus
shown
in Figure 125
The
complete equipment, including the reproducing device or wall meter and
accessories, is
shown in Figure 126.
The
stereoscopic method is really a single-shift triangulation method.
During the war the
United States Army Medical Department perfected an apparatus devised by
the late E. W.
Caldwell, of New York, permitting stereoscopic fluoroscopy. This
method, of course, requires
special apparatus and the instrument is not yet generally upon the
market. The stereo radiographic method is the procedure of choice when
plates are made. In civil practice it is well to make
stereoscopic plates in addition to the ordinary screen localizations.
234
DOUBLE-SHIFT
FIXED-ANGLE
METHOD
A number of single and double shift fixed-angle methods have been
described, all, however,
based upon the same principle. The method of Strohl,24 professor of
physics at the Sorbonne, is as
follows:
At a convenient distance above the tube T (fig.
127), usually on the
diaphragm of the tube
holder, it is easy to fasten a piece of cardboard or aluminum to which
are affixed two bits of
straight wire, W2 and W3, placed parallel on
either side of the midline
W1, so that the distance
between the wires will bear a
FIG. 127.-Method of
similar triangles (double-shift, fixed-angle method)
fixed relation to the
distance O from the cardboard or aluminum sheet to the focus of the
tube. In
other words, in the triangle TW2W3, the distance W2W3 bears a definite relation to the distance W 1 T. For convenience, let us say that the two distances are equal
and that W2W3 equals W1T. If
desired. a third wire may be added at W1, coinciding with
the normal ray. W2Wl, therefore, equals
W3WI. It is a geometrical fact that the distance
between the shadows cast upon the screen by the
wires W2 and W3 will, under these circumstances,
always be equal to the
distance from the screen
to the focus point of the tube,
235
so long as the screen is
held horizontal to the tube. With a small diaphragm opening the tube is
brought directly beneath the foreign body P (fig. 127) and the position
of the foreign body shadow
marked upon the screen at P1and upon the skin directly
underneath. The screen appearance at this
moment is shown at a (fig.
128). Two leaves of the diaphragm are then
opened widely making as lit
and giving the appearance illustrated in Figure 128, b; the
tube is then shifted to the left, during
which movement the shadow of the right wire W2 will also travel toward
the left while the shadow
of the projectile will travel toward the right, until a tube position
will be reached where the two
shadows coincide(fig. 128, c).
This point is marked upon the screen
with a grease pencil. The
FIG. 128.- Screen
appearance at different
steps in the double-shift, fixed-angle method
tube is then shifted in
the opposite direction until the shadow of the left wire, W3,
and of the
projectile coincide (fig. 128, d).
This point is also marked upon the
screen with a grease pencil.
According to the law of similar triangles, the distance between the two
marks upon the screen
equals the distance from the screen to the foreign body; and to
estimate the depth of the foreign
body it only remains to subtract the distance from the screen to the
skin, if the screen itself does
not rest directly upon the skin.
The
distance between the wires W2 and W3 may bear any
given relation to the distance from
the focus point to the plane in which the wires are fixed. It is only
necessary to know this relation
in order to estimate the depth of the foreign body by this very rapid
and accurate method. It is not
necessary to
236
know the focus distance
of the screen or the distance of the tube shift. The wires may be
placed
upon any of the ordinary types of fluoroscopic apparatus without
interfering with the routine work;
one must only know the ratio of the distance between the wires to their
distance from the focus
above referred to.
In
place of the wires, which are sometimes somewhat hard to see through
the denser
portions of the body, one may file upon the two leaves of the diaphragm
three notches (fig. 129),
one directly above the focus of the centered tube, and one on either
side of this central point at any
given distance. The ratio may be varied, just as in the Strohl method.
With the diaphragm closed, one has upon the screen, therefore, three
diamond-shaped, illuminated notches (fig. 129); the two
outermost notches correspond to the shadow of the two wires shown in
Figure 128, b. The tube is
shifted in the same manner, first to the left and then to the right
until the foreign body shadow is
brought to the center of each of the diamonds; these spots are marked
upon the screen with a
grease pencil, and the distance between them measured and translated
into the depth of the foreign
body.
During
the war the so-called "26-degree method"--the distance from the middle
notch to
either of the outer notches being half the focus-diaphragm distance-was
popular among French
radiologists and was widely adopted by
FIG. 129.- Screen
appearance after notching the diaphragm leaves for the Roussel method
our own medical
officers. With this method, only one shift was made from the central
notch to one
of the outer notches, and the distance of the shadow shift multiplied
by two to determine the depth
of the foreign body below the screen.
HARPOON -METHOD
The
harpooning method, the insertion of a sterile needle through the
tissues to the foreign
body, which serve as a guide to the surgeon in removing the projectile,
requires no special
apparatus not found in any hospital with a fluoroscopic X-ray
equipment.
The
instruments, the field of operation, and the surgeon's hands must be
surgically clean,
and a sterile sheet or towel must be held between the operative field
and the fluoroscopic screen. By
rotation and manipulation of the part the approximate anatomical
position of the foreign body is
determined as nearly as possible. The needle when introduced will mark
out the line of the
surgeon's approach; if the track of the needle is likely to pass near
vital structures it is of
importance that this line be determined in consultation with the
surgeon. The path of attack having
been determined and the surgeon having marked on the skin approximately
where he wishes to
make his incision, the part is rotated under the screen so that the
skin mark will be vertically over
237
the foreign body. A
needle of proper length having been selected, it is seized with forceps
and held
at such an angle that the fingers of the operator will not be exposed
to the rays. Under the
fluoroscopic screen, the needle is pushed down upon the foreign body
and left in situ.
This
method has been modified and improved under the name of the"trocar and
cannula
method" by various surgeons of the allied armies. It should always be
used under the direct
supervision of a competent surgeon or of one who has the necessary
anatomical knowledge and
surgical judgment to use it without danger of infecting the patient or
of injuring important struc-tures. In cases with encapsulated foreign
bodies the trocar and cannula method is often of great
value, but it is not useful as a routine procedure in recent wounds,
where the surgeon usually
approaches the projectile or foreign body through the path by which it
entered.
Under
anesthesia, the skin should be punctured with a sharp scalpel, after
which the
cannula, with the obturator in place, is slowly passed into the tissues
until it comes into contact with
the projectile as determined by touch or by fluoroscopic observation at
varying angles. After
contact is secured, the obturator is removed and a piece of piano wire,
bent at the lower end in the
form of a fishhook, is passed well through the cannula. The latter is
then withdrawn, leaving the
piano wire hooked into the flesh. If necessary, the external end of the
wire may be clipped with
forceps or cut off short, and bent down close to the skin. The length
of wire introduced beneath the
skin indicates to the surgeon the depth of the foreign body. It is very
important that the introduction
of the needle or trocar should be carried out with the instrument in
the line of the normal ray; any
attempt to insert it at any angle will result in considerable
mutilation of the tissues.
The
harpooning method is not only a method of localization, but it is also
a method of
guidance for the surgeon during the operation of extraction.
HERTZ COMPASS METHOD
The
use of the Hertz compass is foremost among the methods which serve to
localize, and
to guide the surgeon. This is an apparatus of which several types, all
similar in principle, were
employed during the war. For clinics where there are frequent
extractions of foreign bodies from
the cranium and from the deeper structures of the shoulders, axillae,
lumbar region, pelvis, and
buttocks, this instrument can be highly recommended.
As
originally proposed, this instrument was intended to be used in
connection with
radiographic work, whereby a permanent record should be made for the
later setting of the
compass, provided the identifying skin marks were not obliterated. On
account of the very
considerable time necessary to prepare a negative for examination and
measurement, it has been
found desirable in many cases to operate the compass by data secured
from fluoroscopic ex- amination, which is much more expeditious and, in
many cases, will serve fully as well.
The
essential feature of the Hertz compass is the possibility of adjustment
of the movable
legs that support the instrument, so that when resting on fixed marks
on the body of the patient the
foreign body will be at the center of a
238
sphere, a meridian arc
of which is carried by the compass. This arc is capable of adjustment
in any
position about a central axis. An indicating rod passes through a
slider attached to the movable arc
in such a way as to coincide in all positions with a radius of the
sphere, and whether it actually
reaches the center or not it is always directed toward that point. If
its movement to the center of the sphere is obstructed by the body of
the patient, the amount it lacks of reaching the center will
be the depth of the projectile in the direction indicated by the
pointer.
The
value of the compass lies in its wide possibility as a surgical guide,
in that it does not confine the attention of
FIG. 130.- Hirtz
compass
guidance during a
surgical operation
the surgeon to a single
point marked on the skin, with a possible uncertainty as to the
direction in
which he should proceed in order to reach the projectile, but gives him
a wide latitude of approach
and explicit information as to depth in a direction of his own
selection.
The
compass is shown in Figure 131 and schematically in Figure 132. Three
metal arms
respectively labeled 1, 2, and 3 in clockwise rotation are so mounted
as to turn freely upon a central
pivot and have their upper surfaces all in a single plane. Each of
these arms carries a slider,
which may be adjusted to any position along the length of the arm. Each
slider has an adjustable leg
at right angles to the plane of the arms, that may be held in any
position by a small thumbscrew.
These legs are graduated and the zero point is not at either end of the
legs, but a few centimeters
below the upper portion, which terminates in a small knob. The center
post about which
FIG. 131.- Hirtz compass
the arms rotate has a
hole at right angles to the plane of the arms and is also shaped to
carry the
curved metal are, A. (fig. 132.) The hole in the slider on are A,
carrying the indicating rod, can be
made to coincide with the opening through the center post.
239
When
the legs are set at zero, quite irrespective of the position of the
slider on the arms or
of their angular position, and the compass stands on a plane surface,
the indicating rod, passed
through the slider on arc, A, will touch the supporting plane at the
center of the sphere of which A
is a meridian arc. A friction clip on the indicating rod may be
adjusted in contact with the slider on
A, and the distance from the lower end of this clip to the pointed end
of the indicator will be the
radius of the sphere of which A is an arc.
Figure
133 shows the compass with the legs shifted so that they no longer
stand on the base
plane, and, in fact, are at quite different heights; but the arc, A,
and the arms of the compass have
not been displaced, so that the pointer still reaches the center point,
P, in this plane.
Figure 134 shows the
compass actually set upon the body of a patient, its legs resting on
three skin
marks, M, N, and O, and with the indicating rod pointing toward the
projectile, but failing to reach it
because of contact with the skin of the patient at S. The depth of the
projectile in this particular
direction
FIG. 132.- Schematic
drawing of Hirtz compass with legs adjusted at zero points and with
legs
adjusted at zero points and resting on a plane
FIG. 133 Arms and indicator of Hirtz
compass. Same position as in
Figure 132, but with legs elevated on blocks whose tops might corrspond
to skin markers
is indicated in Figure
134 by d. If, now, the indicating rod is placed in the slider
carried by the arc,
A, the rod touches the skin at a different point, S’, and the distance
between the friction clamp on
the rod and the upper surface of the slider on the arc, A, will be the
depth of the foreign body along
the direction indicated by the dotted line. It is evident from the
construction that the surgeon may
place the arc, A, in any position throughout 360?, and the
slider at any position from the center to
the extreme end of the arc, and still have the indicating rod point to
the foreign body and show its
depth from the point of contact with the skin. Figure 130 shows the
compass in position on the
patient at operation.
The
exact amount which each leg of the compass must be shifted from its
zero point in
order to stand on the marker to which it belongs and yet have the
indicating rod in the proper
position is easiest seen in Figure 135, in which only a single leg of
the compass is shown; but the
same will apply to each of the legs in turn. Imagine a plane, parallel
to the plane of the three arms
of the compass, to be drawn through the projectile. The leg attached at
arm number one
240
standing on the marker,
M, would, if it could pass down to this plane, intersect the plane at
the
point, E, and under these circumstances, the indicator passing through
the central post of the
instrument would touch the skin at S, vertically above P. If the
distance from the plane, from which
measurements are made, to the lower plane, containing the projectile,
is measured and, likewise, the
distance MM’, it is seen that the amount by which this particular leg
is raised from its zero point,
where it would be set if it reached the point, E, will be the
difference between the depth of the
foreign body and the depth of the marker from any plane of measurement,
for example, that of the
fluoroscopic screen ora photographic plate. The fluoroscopic screen may
be placed in any position
parallel to the base plane, EP, and the difference, ME, would be quite
independent of the height of
the plane from which all measurements are made.
This
may be summarized by saying that each rod is to be shifted from its
zero point an
amount equal to the difference between the depth of the projectile
below the fluoroscopic screen, or
other plane of reference, and the depth
FIG 134.- Schematic drawing
of Hirtz compass
set up on skin of patient
FIG. 135.- Reason for shift
of leg of compass
from zero point by the amount stated
of the skin mark upon
which this particular leg would stand, measured from the same plane. It
is
absolutely essential in the use of the compass to adopt a systematic
procedure, so that the arm to
carry the leg is identified with the depth of measurement of its own
skin point.
The
data necessary to properly adjust the compass may now be stated by
reference to
Figures 132 and 135. The indicating rod in the central position and the
three legs of the compass
mark out, in any plane parallel to the base plane of Figure 132, four
points of definite position in
the plane. Any vertical shift of the legs will still allow them to
retain their position in lines passing
through the points, E, F,G, and P. The point G. Figure 132, is then in
a vertical line passing through
the marker, M, and the data necessary to set the compass must give the
position in a plane of these
four points, and in addition to this must give the depth from a fixed
plane, parallel to the base plane,
E, F, G, of the three markers on the skin of the patient and of the
projectile within the patient's
body. Whether this data is to be found by a photographic or at
fluoroscopic process is immaterial.
as the steps in its use will be identical.
241
When
a fluoroscopic method is to be used, an auxiliary device may be found
of considerable
aid in rapidly and accurately securing the requisite data. Such a
device is shown at A, Figure 136,
and consists of three arms, each with a slider very similar to the
original compass. In fact the latter
may be used with rather less convenience by removing arc, A, and
allowing the indicating rod to
project a short distance below the center, with the legs temporarily
removed. The auxiliary compass
has its arms numbered in the same way as the original Hertz compass and
has a projecting pin
which fits the perforation in the screen. One of the arms is rigidly
attached to a ring concentric
with the axis of rotation about the pin, while the other two are
movable, but may be clamped by
thumb nuts to the ring. It is evident that placing the perforation in
the screen in the vertical ray
passing through the projectile definitely fixes the position of the
center post. If, then, each marker
in turn is brought into
FIG. 136.- Accessory
apparatus for
fluoroscopic work with Hirtz compass. A, Auxiliary compass, pedestal
support, and three markers with friction clips, B, Hirtz compass
mounted with the three legs at different levels, so that a
pointer reaches white spot on the base plane at the center of the
sphere of which the curved arc is a part
the vertical ray and the
arm and slider adjusted so that the hole in the slider matches such a
projection of each marker, the three openings in the sliders and the
central pin fix the four points
which it is necessary to obtain. It then remains to determine the depth
of the projectile, for which
one of the methods, A, B, or C, should be employed and also to
determine the distance from the
screen to the opaque markers. When using the fluoroscopic method, the
latter depth can be very
readily determined by simply passing a suitable measuring rod through
the perforated screen, which
has been brought into the vertical ray passing through the marker. This
depth is to be recorded and
accurately identified with the arm carrying the slider corresponding to
that particular skin marker.
In order to facilitate this measurement a set of three measuring rods
with friction clips, differing
slightly in shape, are provided. As soon as these four depths and the
four marks in the plane of the
screen have been
242
determined, the work of
the roentgenologist is completed, provided he has made sure that the
skin
marks are plainly visible. The adjustment of the compass may then be
carried out by an assistant to
either the roentgenologist or the surgeon, after which the instrument
can be sterilized and is ready
for the surgeons use.
FLUOROSCOPIC METHOD, WITH AUXILIARY COMPASS
Find
the shadow of the projectile, Po, on the screen, and reduce the size of
the diaphragm,
keeping the shadow in the center of the illuminated area. Adjust the
screen so that the opening at
the center of the screen coincides with the center of the shadow, lock
screen carriage in this position for all except vertical travel. Mark
the skin through the opening by use of the special
marker provided. Determine the depth of the projectile by either method
A. or C. Raise the screen and attach three metallic markers (preferably
three small washers) to the skin at suitable
points, and mark the skin at each point selected. Choose skin points
with care to ensure: No in- terference with probable incision; proper
stability of the compass; as firm foot points as possible.
Lower the screen near to or touching the skin, with the central hole
still in the vertical ray through
the projectile, and insert the pin
FIG. 137. - Method of
showing fluoroscopic
adapter with Hirtz compass
of the auxiliary compass
in the hole. Be sure that the screen is locked in position. Bring arm
marked
1 to point toward the operator's right and loosen thumb nuts on arms 2
and 3. Shift the tube to bring
the right-hand marker in the vertical ray (leaving screen locked), and
adjust the slider on arm No. 1
so that its opening coincides with the projection of the marker, Figure
137. If washers are used the
round opening is easily identified. Do the same with each of the other
two markers, insuring that
No. I does not move when adjusting the others (a small clamp will aid
in this) and lock each arm.
The central pin and the three sliders then give the positions for the
arms and sliders of the compass.
Remove the auxiliary compass and determine the depth of M, N, and O
below the upper surface of
243
the glass on the screen.
For the depths of M, N, and O use the small rods provided with friction
sliders and make the measurement by passing the rod through the
perforation in the screen, which,
for this purpose, is to be brought vertically over each marker in turn.
If the friction clips are then
pushed down until they touch the glass and are properly adjusted as to
friction, the distance from
the clips to the end of the rod will indicate the depth desired. These
sliding clips are shaped to
correspond to the projecting blocks on the sliders of the auxiliary
compass, and care must be taken
to use them in their proper places, so that there is a complete
identification of the compass slider
and the depth of the marker corresponding. Form the habit of using
these in a definite order, during
these depth measurements, to minimize chances of error. If no further
fluoroscopic work is to be
done these depths may be determined in daylight. Otherwise use the
vertical ray from the tube.
SETTING THE
HIRTZ COMPASS
By
use of the auxiliary compass.- (1) Remove the arc and the indicator
rod; lower the three
legs until the upper (rounded) ends project 1 to 2 cm. (2) Lay the
auxiliary compass on a flat
surface with the center pin upward. Invert the Hertz compass and place
the central hole on the pin
of the auxiliary. Unlock wing nut at center of compass, thus releasing
the arms; bring arm No. 1
and its slider to such a position that on loosening leg No. 1, it will
drop into hole of the No. 1 slider
of the auxiliary. Tighten set screws of slider and of leg No. 1 (fig.
138). Proceed in the same
manner with arms, sliders, and legs Nos. 2 and 3. Tighten wing nut at
center of Hertz compass, thus
locking compass arms. (3) If pedestal support is provided
FIG. 138.- Setting arms and
legs of Hirtz
compass directly from the
auxiliary compass
set the lock sleeve on the vertical rod, so that when the pedestal
stands on a
flat surface,
and the Hirtz compass is placed thereon, with the pedestal rod through
the central bole of the
compass, it will be supported in such a position that the legs will
drop to their zero points when
loosened, leaving the compass supported on the pedestal. (4) Shift each
leg an amount equal to the
difference between the depth of the projectile and the depth of the
skin marker on which each
individual leg is to stand. (Leg No. 1 stands on skin marker No. 1,
etc.) Tighten each leg,
244
replace compass arc and
indicating rod, the latter with lock sleeve properly set, and the
compass is
ready for sterilization and use by the surgeon.a
It
is recommended that even if the compass is to be immediately set direct
from the
auxiliary a record of the data necessary for setting be made and
retained until after the operation.
From
the diagram of data.- (1) The auxiliary, having been set to mark
shadows on the
screen, is placed on a plain sheet of paper with center pin down.
Indicate with a pen the spot on the
paper where the pin touches and mark it PO (being directly over the
projectile)--a small drawing
board with a hole in the center, in which the pin may be inserted
through the record paper, may be helpful. Indicate the locations of the
holes in sliders 1, 2, and 3, thus giving their relations to PO;
identify each by number and write opposite each the depth in
centimeters to the skin below the
fluoroscopic screen. The depth of PO below screen must be similarly
indicated. (2) Take the Hertz
compass with indicating rod inserted in central hole, and set point of
indicating rod on PO of
diagram. Loosen wing nut at compass center, thus releasing arms; bring
leg No. 1 to stand on mark No. 1 of diagram. Proceed identically with
legs Nos. 2 and 3; then, with indicating rod and the three legs
accurately
FIG. 139.- Detail of holder
for direct setting
of Hirtz compass
on the proper points of
diagram, tighten wing nut to lock compass. Tighten all set screws. (3)
Place
the compass on pedestal support and proceed as indicated in paragraph 4
above. The instrument is
now ready for sterilization and use by the surgeon. Care must be taken
to avoid handling the
compass in any manner that would displace any of the settings. In case
of deferred operation, the
four skin marks should be tattooed, or they must be renewed with
sufficient frequency to insure
their identification at time of operation. If metal washers are used,
they may be sterilized and
attached at the time of the operation; they serve very well to hold the
compass legs on their proper
skin points.
Direct
setting of the Hertz compass.- Several devices for holding the
Hertz
compass in order
to make a direct adjustment of the foot points and leg heights on the
patient have been proposed.
This method possesses two distinct advantages: It may be done quite
expeditiously; it indicates
clearly to the operator how the compass is going to stand on the
patient when in use. Its
disadvantages are: The necessity of considerable illumination in the
fluoroscopic room when
placing the compass; danger of movement of the patient between
localization and final adjustment;
need for the compass both in the fluoroscopic rooms and in the
operating room.
In
order to adapt this method to the standard table, the design shown in
Figure 139 has been
developed. This consists of a tube fitting into the socket of the
screen carrier, holding a square
sliding rod with an end socket taking the hub of the compass.
a This subtraction can conveniently be
made by laying off on paper the distance from the top of the lead glass
on the screen to P, then, placing auxiliary rod No. I with its sleeve
indicating the skin depth for marker No. 1, mark this
distance on the line previously made, and reset the sleeve to the
length remaining on the projectile depth line.
245
The
collar, A, on the tube has a V-shaped projection intended to fit a
notch in the carrier
socket so as to prevent rotation from a definitely determined position.
The
fundamental principles in this method are the alignment of the central
axis of the
compass with the vertical ray through the projectile, and the bringing
of the compass to the proper
height so that the top of the slider on the arc, when in its central
position, is at a distance from the
projectile equal to the radius of the arc.
In
order to secure the former, the holder should enable us to readily make
the plane of the
arms level. Then the compass should be allowed to move up or down in a
vertical direction without
rotation. When the indicator is placed in the central position and the
compass is properly placed on
the patient, the radius mark on the pointer will be as far above the
arc slider, through which the
pointer is inserted, as the measured depth of the projectile along the
vertical ray. While rigidly held
in this position the arms and legs may be adjusted at will to support
the compass in this position. (Fig. 140.)
Care
must be taken to insure that the patient does not move between the
localization and
the completion of the adjustment; that the pointer is raised from its
zero the correct distance; that
all parts of the compass are locked before removal from the body.
FIG. 140.- Direct setting of
Hirtz compass.
Compass and holder in position
The
holder must be adjusted before it is used the first time as follows:
Remove screen-holding rod from the horizontal socket and insert holder.
Remove arc from the compass, insert hub in the holder, and place two of
the arms close together so that the line of the holder bisects the
angle between them. Then lock the center arm clamp. Place a small level
on the two arms
perpendicular to the holder rod, and rotate rod until this shows level,
then clamp by socket set-screws. Make a scratch mark where the V on the
ring comes in contact with
the socket. Remove
the holder and file a small notch with a triangular file to take the V
on the collar. Test out as to
level, when the holder is replaced in the socket with the V engaging
the notch. If not quite
correct,
loosen the set-screws at the end where the square rod enters, rotate to
level, and fasten firmly.
246
The
above steps need to be done only once and the following procedure for
use is then quite
simple: Remove arc from the compass and insert in the holder, fastening
with the thumb nut, B. Set
the sliding clamp on the indicator rod at the ring mark; I. e., so that
the distance from the lower end
of the slider to the pointed end of the indicator is the radius of the
arc. Insert indicator in the
compass holder and raise until the distance from the top of the brass
holder to the lower end of the
sliding clamp is the projectile depth below the skin mark. Fasten by
nut C. Raise the legs of the
compass and adjust the holder until the lower end of the pointer rests
on the skin mark. Lock carrier in position. Place arms and feet as
desired so that the latter rest on as firm skin points as
possible, and clamp all parts of the compass. Raise compass slightly by
the vertical move- ment of the carrier, mark skin points for the feet,
and identify them clearly. This method is much
more convenient than to mark the skin first and then adjust the compass
to fit the marks. Remove compass, read and record height settings of
legs, then record position of foot points, and
center for resting the compass later if it should be necessary. For use
in the operating room the
compass may be sterilized by a flame.
USE OF THE HERTZ COMPASS WITH PLATES
FIG. 141.- Centering of
tube above plate holder on
cassette with small cross wires, photographic method, Hirtz compass
When
it is desired to
establish the data necessary for the use of the
compass with photographic plates or films, it is necessary that two
exposures be made from two
different target positions, either upon a single plate, or upon two
separate plates or films, without
movement of the patient or skill markers. The latter method is usually
preferred.
There
is furnished for this work a small, flat square of celluloid into which
are inserted two
small steel wires forming a right-angled cross. The celluloid has two
holes punched in diagonally
opposite corners, through which a tape may be passed, and this is to be
tied around the tunnel plate
changer so as to fix the desired centering mark, when two plates or two
films are to be used.
247
Figure
141 shows how the tube is centered, using a plumb line to secure exact
position. This must be done before the patient is placed in position,
and care must be taken not to disturb the
adjustment.
Figure
142 shows the tube, patient, and markers in position for one of these
exposures. One
should not forget to attach to the plate tunnel the marking device or
to use the three metallic
markers in contact with the patient's skin at points properly chosen
and marked for identification.
The
principle of the method is shown in Figure 143. A small marker, X, is
placed
approximately at the center of the plate, if one plate is to be used,
or on top of the plate changing
tunnel, if two plates are to be exposed. Let CX be a perpendicular
FIG. 142.- Skin markers,
plate holder, and
tube holder in position for photographic method, Hirtz compass
erected to the plane of
the plate at the
point X and extending upward a distance of 60 cm. Let F 1 F 2 be positions of the
focus in a line parallel to the plane of the plate at the level C, and
assume that CF 1, and CF2 are
each three centimeters in length. Suppose that M is one of the markers
on the
patient's body. When an exposure is made with the target at F 1,
the shadow of M will fall on the plate at M 1 and, when an
exposure is made from the position F2, the corresponding shadow will be M2.
Had
the exposure been continuous during the motion of the target from F1. to F2,
there would have been
found on the plate a straight line of shadows connecting M1,
and M2. If we drop
perpendiculars
from the two
FIG. 143.-Schematic
representation of plate,
cross-wire marker, ,marker, and tube
focus
positions for radiographic use Hirtz compass
focal positions to the plane of the
plate, intersecting it at the points F'1F2,
we see that F',F1M1 is
a plane perpendicular to the plate and passes through M 1,
and the trace of
this
plane upon the plate is F1 M 1.
248
In
the same way a plane passed through F2F'2M2 will be perpendicular to the plate and its
trace will be F'2M2. It follows from geometry that the intersecting line of these
two planes, MMo,
will be a line passing through the point M and perpendicular to the plate.
Consequently Mo is
the
foot point of this marker on the plate to be used in the compass
adjustment. Also the lines M 1M 2,
F' 1,F' 2 and F 1 F2 are
parallel.
Figure
144 shows part of a developed negative upon which there appears a
shadow at M l, a
shadow at M2 and a
single image of the marker on the plate a single image, since its
motion is zero
or nearly so, the marker being most in contact with the plate itself.
If one joins M l and
M 2, by a
straight line and then draws through the center of the cross a line
parallel to M1 M2 and measures a
three centimeter length on, this line through X in each direction from the center
of the cross, the
points so determined will be F1, and F2 of
Figure
143. Cross connection between the ends of these
lines, that is F'2 M2 and F'1, M1 then definitely locates the point M which will be the foot point
sought.
FIG. 144.- Construction for
finding one of the
foot points M from the shadows of a corresponding marker as shown at M 1 and M 2, and the shadow of the cross marker X
FIG. 145.- Complete chart
for setting feet of
Hirtz compass
The
length of the line MM2 will clearly decrease as M is placed nearer the
plate, and
increases as it is raised. For the definite 60-cm. target-plate
distance and 6-cm. tube shift there
corresponds one height MMo for one image shift M1M2.
These relative values are shown in Table
26 in which all measurements are given in centimeters or tenths of
centimeters.
Figure
145 shows a full construction and necessary record derived from the
photographic
plate used in setting the compass. This data is used exactly as was
that derived from fluoroscopic
examination.
It
will require a considerable amount of skill and judgment to so place
the markers on the
patient's skin as to give reliable readings and at the same time
furnish proper support for the
compass. These data are used exactly as were those derived from
fluoroscopic examination. It
will require a considerable amount of skill and judgment to so place
the markers on the patient's
skin as to give reliable readings and at the same time furnish proper
support for the compass when
used at operation. Especially one must insure that the shadows of all
the markers fall on the
photographic plate. It is also clearly undesirable to have the lines
whose crossings are to indicate
foot points for the compass setting too nearly parallel, as in that
case a slight error in their location
may bring a decidedly large shift in the position
249
of foot points.
Transparent celluloid scales arc sometimes furnished, which assist
somewhat in
determining whether the shadow of the markers will fall on the plate.
Knowing
approximately, by previous fluoroscopic or other examination, the
position of the
projectile whose localization is sought, select a plate changer of
proper size, attach the cross, and
place on the table in the position to which it is to be used.
By
means of a plumb bob, adjust the tube stand so that the central
position of the target shall
be vertically over the metallic cross, and be sure that the distance
CX, Figure 143, is 60 cm. Adjust
stops to allow the tube to move 3 cm. in each direction from the
central point.
Place
the patient on the tunnel plate changer, taking care that the cross,
plate changer, and
tube are not displaced in the process. Or, if the tube holder is
rotated, fix stop for its exact return.
Make sure that the tube is three centimeters from its center point and
insert a plate. Place the three
skin markers in the desired position. The balls as furnished with the
apparatus may be used, or
small metallic markers, preferably V-shaped, may he attached to the
patient's skin with small pieces
of adhesive. Make the exposure needed. Remove the first plate, shift
the tube, and make the second
exposure. Do not attempt to get the data from the plate, or film until
it is dry. If it is once scratched
or smeared, it will be impossible later to get good measurement.
FIG.
146.- Equipment
supplied for use with Hirtz compass
If
the exposures are to be made on a single plate, be sure not to
overexpose. When using
two plates, the image of the cross is used to superimpose the plates
and to transfer the data to the
record sheet.
Make
the record described above, locating the foot points and the center
points. Read
M1M2, N1N2, O1O2,
and P1P2, in centimeters and fractions, enter
these on the record under column
marked spread, and enter under height the corresponding number in Table
26. Thus:
CHART
The equipment supplied
for use in method E is shown in Figure 146.
250
TABLE 26.- Measurements
for use in connection with Hertz compass [Focus plate
distance, 60
cm.; tube shift, 6]
The
advantages of the Hirtz compass in selected cases are numerous. After
the sterilized
compass has been placed in position, the penetration needle, when
brought in contact with the skin,
indicates the point where the incision should be made, and the depth
and the direction in which the
foreign body lies. By means of the rotating device through which the
penetration needle is passed,
the surgeon can select the point of entry without in any way
embarrassing the usefulness of the
instrument. The instrument, being sterile, can be re-applied as often
as needed during the operation.
In
using the compass, it is important that the skin marks selected for the
compass legs
should constitute a large triangle and that these marks should not be
covered by drapes or towels
during the operation. When the compass is being set, the patient should
lie in either the prone or the
supine position rather than on the side, and at operation exactly the
same attitude should be
assumed. It is important that the muscles be relaxed as far as
possible; otherwise muscular
contraction maintained during the X-ray examination is likely to
disappear during anesthesia and
thus possibly alter the position of the projectile to a considerable
degree. Duval 25 cites a case in
which a bullet located in the adductors of the thigh shifted eight
centimeters when the contracted
muscles were relaxed.
DEPTH OF ANATOMICAL LANDMARKS BENEATH THE
SKIN
The
table given below is of value in determining the exact position of a
foreign body in
relation to points on the skeleton. In their article published in
connection with this table, the authors
state that the surgeon often experiences many difficulties when
operating for the removal of a
foreign body even after the roentgenologist has made an accurate
localization.26 Previous to the
war, the surgeon studied the ultimate depth of his operation only with
regard to certain surrounding
anatomical landmarks, and not in terms of centimeters or inches beneath
a point on the skin. If the
roentgenologist reports a projectile as being 4.5 cm. from a point on
the skin of the back overlying
the trans-verse process of the 12th dorsal vertebra, the surgeon has
little knowledge as
251
to where this depth will
lead him. If, however, the surgeon knows that the average depth of this
structure is less than 4 cm. from the skin, he appreciates the fact
that the projectile must lie in or
just anterior to the transverse process. The objection is, of course,
that individuals vary greatly in
thickness of various parts, but the authors call attention to the fact
that the soldier is selected after
rigid examination and, as a result, the extremely thin and extremely
obese are not present.
TABLE 27.- Depth of
anatomical landmarks
252
TABLE 27.? Depth of
anatomical
landmarks?Continued
EYE LOCALIZATION
In
the case of foreign bodies in the eye, very accurate localization is
necessary, as
knowledge of the exact position of the foreign body may mean the saving
of an eye or the preservation of vision.
The simple Sweet-Bowen
apparatus consists of two general parts--the base or headrest, as
illustrated in Figure 147 and the localizer, as shown in outline
drawing, Figure 148. The headrest base is composed of the following
parts: A. plate-slide tunnel, so constructed as to protect
one-half of a 5 by 7 photographic plate while the other half is being
exposed,
and to protect the exposed half while the second
FIG.
147.- Headrest
for
use with the eye localizer
exposure is being
made. Four rubber-tipped legs to raise the tunnel so that it will act
as a pillow
to hold the patient's head level when lying on his side. A plate holder
having a slide that will protect
the plate from the ordinary light, but offer no resistance to the X
ray. An arm or handle attached to
the plate-holding slide to enable the operator to shift the plate the
correct distance for each
exposure, and to withdraw the same when both exposures have been made.
A pneumatic cushion
for the comfort of the patient. A double clamp to hold the patient's
head and to prevent any horizontal movement. A single vertical clam to
press the head downward upon the pneumatic
cushion. The localizer consists of a heavy metal base, Figure 148; an
upright standard, B, to
support the localizer and permit the
253
same to be adjusted and
held firmly at any desired height. The indicator ball D, with its
needle-supporting item D2, which, when properly adjusted to
the center
of an eye, will cast its shadow on
the photographic plate and serve asa landmark to indicate the center of
the cornea.
The
metal tip E, of stem E2 is made cone shaped, so as to more
easily
differentiate its
shadow from that of ball D. These indicators are permanently adjusted a
known distance apart (15
mm.), and the base of the localizer is provided with two holes exactly
15 mm. from center to center,
which should be employed to verify this adjustment in case of doubt.
When an X-ray plate is made
of them obliquely, adjusted to an eye as above stated and as indicated
in "front view" on the chart,
we are enabled by their shadows to definitely locate the source and
course of the rays of flight (in
relation to the chart) that caused the shadows. Also, the position of
any foreign body that may show
on the same plate can very easily be determined by the position of its
shadow in relation to that of the ball and cone,
because the exact position of the latter with reference to the chart is
known and
indicated (front view).
Tube
C12 and notch F18 are sights similar to those
used on a rifle, with which the operator
can accurately align the center of the cornea of the afflicted eye with
ball D and its supporting step D 2 F14 is a
spring trigger which presses upwards against pin F.13 F5 is the end of the rod to
which the indicator-ball and cones D
FIG. 148.- Sweet eye
localizer
and E are attached by
bracket F, the whole being supported by passing through tube C.5 Spring F14 being attached to stationary tube C5 by means of bracket C7 rod F5 with bracket F6 can be
pressed
forward until pin F13 is engaged by notch F.15
By
loosening set screw C4 the bracket C can be raised or
lowered until ball D, with its
supporting stem D,2 is in exact alignment with the center
of the cornea of the affected eye, and the
screw is then tightened.
The
patient is instructed to close his eyes, and the entire instrument,
with its base, is slid
forward until indicator ball D presses into the eyelid approximately
its thickness. The trigger F17 is
then depressed to disengage notch F15 from pin F13,
when spring F16 will cause the rod F5 and
indicator-ball D and cone E to rebound exactly 10 mm., being restricted
by knob F7 in slot C.6 The
subject and localizer are now in correct position for making the two
necessary exposures.
FIRST EXPOSURE
Place
patient's head, affected eye downward, on the plate-holder base, with
inflated cushion
in position, as shown in illustration, being careful that the
254
inflated cushion does
not extend over the marked lines on the cover-otherwise it will cast a
shadow
on the photographic plate.
If
the subject shows a tendency to move about, the horizontal clamp, as
shown in Figure
147, must be adjusted to the base of the head and forehead, otherwise
the vertical clamp, as shown
in illustrations herewith, will be sufficient. The double horizontal
clamp can be adjusted for either
eye by means of its two off-center holes and clamp screws.
Place
the diaphragmed tube in position so that its central rays will exactly
parallel the front
vertical plane of the patient's eye, as shown in Figure 149.
A
plate, having previously been placed in the plate holder, is now placed
in the tunnel with
the outer flange protruding, as shown in illustration. This will expose
one-half of the plate to the action of the rays, while the other half
will be protected for the second exposure.
The
localizer (fig. 148) is now placed on the stand in front of the
affected eye; its trigger is
"set" as already described and, after the indicator ball has been
adjusted to the plane of the cornea, the entire instrument is pushed
forward on its base until the ball presses into the patient's closed
eyelid approximately
FIG. 149.- Position for
first exposure in
localization of projectiles in the proximately its thickness; eye. Be
certain that
the tube is centered accurately over the cone so the trigger spring is
then that both ball and cone will be superimposed
released and the
indicator ball and cone recede exactly 10 mm., thereby permitting the
patient to
open his eyes and wink them in a natural manner. By referring to
localizer chart you will observe
that due allowance of 10 mm. has been made by placing the indicator
ball and cone just that far
from the front plane of the cornea. It should also be borne in mind
that the front of the cornea is 10
mm. in front of the shadow of the indicator ball, as shown in your
negatives. The tube is now
centered over the localizing ball and cone so that the shadows of the
two will coincide (fig.149). Some object, such as a candle or a piece
of white paper, that can readily be seen by the patient,
should be placed in alignment with the sights of the indicator, but
several feet removed therefrom,
and the patient should be instructed to look constantly at this object
while the two exposures are
being made.
255
SECOND EXPOSURE
The
first exposure having been made with the rays perpendicular to the
plane of the plate
and parallel to the patient's eye, thereby superimposing the shadows of
the indicator ball and cone
and their supporting stems, as shown in the right-hand half of
illustration (fig.150) the X-ray tube is
then shifted toward the patient's feet four or five inches and tilted
so that the indicator rod points to
the ball of the localizer, thereby causing the central rays to pass
obliquely through the center of the
cornea of the patient's affected eye, as shown in Figure 151
FIG.
150.- Specimen plate
of projectile in the eye, illustrating the method of measurement
The
photographic plate
must now be shifted by pushing the plate holder inward, by its handle,
as far as it will go, thereby protecting that portion that was acted
upon by the rays in the first exposure
and bring its unexposed half in proper position to receive the rays
from the second exposure. In this position the second exposure is made
with the rays falling obliquely upon the indicators,
thereby separating their shadows, as shown in left half of
illustration.
It
should be remembered that it is not essential that the exposures be
made with 4 the
tube at any specific distance from the plate, or even that it be the
same distance from the two exposures. Neither is it important that
FIG.151.-
Second
exposure
for localization of projectiles in the eye. Notice shift of tube in
order to
separate the shadows of ball and cone. Be careful not to produce any
lateral shift. The tips of ball
and cone second exposure, as by the must he kept in alignment
the tube be shifted an
exact or known distance for the second exposure, as by the use of the
charts
and Sweet's method the course of the ray is automatically established.
This is shown by the line A-D through P 1 and P 2 of outline drawing, Figure 152.
256
CHARTING THE PLATES
In
charting the plates the following method is pursued: Upon the negative
(right-hand half
of the illustration) which represents the first exposure, a line is
drawn through the horizontal axis of
the indicator ball and cone which are here superimposed, thereby
projecting their supporting stems
and establishing the visual axis of the eye (fig. 150).
A
second line is drawn at right angles to the first through the center of
the foreign body's
shadow.
With
a small pair of dividers step the distance from the edge of the
indicator ball to the
intersection of the horizontal and vertical lines that you have just
drawn. Then step this distance off
on the diagram chart, making a dot with a pen, or a very sharp, hard
pencil, to represent the exact
distance (distance R. fig. 152).
FIG. 152.- Schematic
drawing of localizing chart, illustrating the method of obtaining
measurements
On
the vertical line that has been drawn through the shadow of the foreign
body (right-hand
half of fig. 150) measure the distance of the foreign body above or
below the horizontal line and
indicate the same on the chart above or below the axis, distance V
locating dot F1.
Place
another dot on the same horizontal plane and draw a line through these
two dots,
parallel to the axis, projecting into the front view as shown.
Since
the position of localizer ball B, as shown on the chart, side view, is
the same as when
the first plate was made, the location of the foreign body must be at
point Fl. We have yet to
establish its location to the nasal or temporal side.
Project
a line vertically through point F1 to the 450 angle (see
fig.
153),thence horizontally
through the horizontal section.
257
Upon
the negative (left-hand of illustration) which represents the second or
oblique
exposure, a line is drawn through the horizontal axis of both the ball
and the cone, thereby
projecting their supporting stems and establishing the relation of
their horizontal planes to that of
the foreign body.
A
third line is drawn at right angles to the first two through the center
of the foreign-body
shadow.
With
dividers the distance of the shadow of the foreign body above or below
the horizontal
plane of the shadow of the ball is measured, and the same is marked by
a dot on the front view of
the chart just above or below the center B, as indicated by distance X,
because that was the relative
position of the indicator ball when it cast the shadow. The distance of
the shadow of
FIG. 153.- Chart used in
eye localization
foreign body above or
below the horizontal plane of the shadow of the cone is measured, and
the
same marked on the chart at the point above or below C indicated by
distance Y, because that was
the relative position of the indicator cone when it cast the shadow.
A line drawn through dots PI and P2 will
represent
the true course of the rays in the second
exposure, and its intersection with the projected line from the side
view through the point F1 will
be the position of the foreign body when viewed from the front, while a
vertical projection through
the horizontal section shows the position of the foreign body to the
nasal or temporal side at point
F.
In
these eye localizations a source of error is the fact that this is a
schematic eye,
constructed to correspond to the average eye which is about 24 mm. in
diameter, but this may vary
3 mm. from the average.
258
Sometimes
the variation can be measured with an opthalmoscope and corrections
made, but
ordinarily the eye is so injured that this is impossible, and we must
assume that the eye corresponds
to the schematic eye. This error, of course, would interfere only in
cases where the foreign body is
located 1 or 2 mm. inside or outside the sclera. In that event one
would not be certain whether the
foreign body was within or without the globe of the eye.
This
point may often be determined in the following manner: Place the
patient on his side
with the afflicted side next to the plate and center the tube over the
eye. Fix the vision of the good
eye on a spot in a plane parallel to the plate, so placed that the eve
is rotated toward the top of the
head. Make an exposure of one-half the correct amount, then shift the
vision to a point well toward
the feet, still keeping the head fastened securely in place, and expose
the remainder of the necessary
time.
If
there are two images of the foreign body, it is certain that the
foreign body moved with
the eye and therefore must be in the globe.
It
is barely possible for the foreign body to be in an ocular muscle and
move, thereby giving
two images, but its position near the exterior and anterior portion of
the globe would help
differentiate this.
In
an acute case where a localizing apparatus is not available, this
method may be all that is
necessary.
EXTRACTION
X-ray
guidance during surgical operations is indispensable for the
expeditious removal of a
certain proportion of foreign bodies. It is applicable not only to the
extraction of projectiles and
other foreign metallic substances, but also for the removal of
pathological foreign bodies, such as
renal calculi, encountered in civil life. In fact, if there is any
question as to the location of an
elusive stone or doubt as to whether or not all stones have been
removed, it is possible, by means of
the fluoroscopic bonnet and portable X-ray equipment, to make an X-ray
examination of a kidney
which has been lifted out of the wound at operation. This method of
screen control is also useful
during the injection of opaque fluids into the urinary tract, during
the aspiration of intrathoracic
accumulations of fluid, and in the control of injection of air, oxygen,
and other gas into the pleural
or peritoneal cavity, or into the ventricles of the brain.
The
method of intermittent fluoroscopic control is more satisfactory for
general use in the
extraction of metallic foreign bodies than are electro vibrators,
telephone probes, or other similar
devices, for the reason that a considerable percentage (approximately
one-fifth) of the foreign
bodies of war are not magnetizable. Fluoroscopic control methods save
time, lessen trauma, and
conserve the temper of the surgeon.
The
requirements for the malleable band, harpoon, and Hirtz compass methods
have
already been sufficiently referred to in the preceding section.
Two
other methods of fluoroscopic control will be described in detail: The
method of the
open screen in the darkened room, and the bonnet method in the usual
light of the operating room.
FIG. 154.- EXTRACTION OF A
FOREIGN BODY UNDER
FLUOROSCOPIC CONTROL. THE OPEN SCREEN
METHOD IN DARKENED ROOM. THE RED LIGHT ABOVE THE TABLE SERVES TO
ILLUMINATE THE
SURGICAL FIELD IN THE PRELIMINARY STEPS BEFORE THE DIRECT SEARCH FOR
THE FOREIGN BODY
BEGINS. BY MEANS OF THE FOOT SWITCH THE RED LIGHT IS TURNED OUT AND
CURRENT IS
TURNED INTO THE X-RAY TUBE BENEATH THE TABLE, AS ILLUSTRATED IN FIGURE
155
FIG. 155. -THIS ILLUSTRATION
REPRESENTS THE
RADIOLOGICAL STEP OP THE PROCEDURE OP
LOCALIZING FOREIGN BODIES UNDER FLUOROSCOPIC CONTROL. THE ROOM IS IN
DARKNESS
EXCEPT FOR THE FLUORESCENCE PROM THE SCREEN DURING THE ACTUAL X-RAY
LOCALIZATION
259
OPEN SCREEN IN DARKENED ROOM
The
requirements for this method are the usual fluoroscopic horizontal
table; a fluoroscopic
screen; a proper overhead red or green light, sufficiently bright,
preferably under control of the
same foot switch that controls the X-ray current; surgical equipment,
including sterile sheets,
gloves, gowns, and instruments.
No
instruments of special design are needed except a pair of narrow-jawed
forceps. A
special bullet-seizing forceps or a forceps of the type used for
exploration of the gall bladder or
common duct is usually satisfactory for grasping the foreign body. The
forceps of Wullyamoz are
bent at a right angle in such fashion that the prehensible portion of
the instrument is held in the line
of the vertical ray without exposing the hand of the operator.
If
it is not convenient to use the ordinary horizontal fluoroscopic table,
any wooden or
aluminum topped table will suffice if so constructed that an X-ray tube
can be placed beneath it
without danger of short-circuiting the current. The modern bedside
equipment (fig. 156) is very
satisfactory for this purpose. The small Coolidge tube at the
tube-holding arm can be turned
downward and placed under the table at a point vertically beneath the
foreign body when the patient
lies in the position for operation. Blankets of black or green cloth
draped around the table to the
floor will prevent the escape of light into the room,
FIG. 156.- Arrangement
of
the tube and table for the bonnet method
or a smaller piece of
black cloth can be placed directly around the tube for the few moments
necessary for the examination. The ordinary horizontal fluoroscope is,
of course, already equipped.
In
military hospitals in the forward area there is seldom need for the use
of the open screen
in the darkened room. When this method is required the patient can be
carried into the X-ray room
and the surgery done there. This method interrupts, of course, the
routine work of the X-ray
department and hence for forward hospitals the bonnet method, described
below, is preferable, as it
can be carried out in the operating room. In stationary hospitals,
where there is likely to be more
time for deliberate work, the writer considers it desirable to provide
a special room for extraction of
foreign bodies under X-ray control, employing the method of the open
screen in the darkened room
for a certain percentage of difficult extraction cases.
One
may use the ordinary lead-glass covered, fluoroscopic screen: or an old
intensifying
screen, no longer useful for radiographic work, may be fastened
260
to a piece of lead glass
by means of adhesive tape and held by an assistant whose hands are
properly protected by leaded rubber gloves. Special tables were
constructed during the war supplied
with a hinged arm for holding the fluoroscopic screen, so that when the
screen was not in use it
could be tilted back out of the way of the operator.
For
the overhead light one may employ an ordinary incandescent bulb,
stained red. This red
light may be as brilliant as the surgeon desires. The writer prefers a
bluish bulb mounted in a
yellow globe, which gives a very agreeable light, much like moonlight.
On the other hand, the
overhead light in daily use in the fluoroscopic room may be utilized in
place of a red light for most
of the manipulations; if at any stage of the operation more
illumination is required, a headlight may
be supplied to the surgeon. Where extractions under X-ray control are
frequent, it will be
advantageous to provide a special source of overhead light, 5 or 6 feet
above the fluroscopic table,
so arranged with glass filters that a powerful red light is thrown upon
the operative field. If this
light is equipped with a rheostat for dimming or intensifying the
illumination, it will be all the more
serviceable. In the absence of more elaborate equipment, a hand lamp
equipped with a red bulb will
serve.
Before
the operation it is important that both the surgeon and the radiologist
spend ten or
more minutes in an abscurely lighted room, or with the eyes protected
by smoked glasses.
After
the patient has been made ready upon the table, and the sterile linen
has been arranged
as for any aseptic operation, an additional sterile sheet, known in
France as the velum, is thrown
over the operative field and fastened down by towel clips on the side
next to the radiologist,
opposite the surgeon. On the side next to the surgeon, the sheet is
held at its two corners by sterile
forceps in the hands of assistants. These assistants may or may not be
dressed for sterile work as the
circumstances warrant. The assistants holding the front ends of the
velum drop it over the operative
field, protecting it from the radiologist and his unsterile screen.
Figure 154 shows the operating
scene at this moment. The red light is then extinguished and the X ray
is turned on (fig. 155). The
radiologist adjusts the tube under the table so that only a small spot
on the screen, not more than 3
cm. square, will be illuminated, and the foreign body is brought to the
center of this spot. The tube
is then fixed in position and the radiologist makes pressure against
the skin with a sterile pointer at
a spot directly over the foreign body.
The
surgeon notes the point on the skin thus indicated and, if it is a
satisfactory path of
approach to the projectile, makes his incision there. The radiologist
then steps back. the velum is
raised, care being taken not to contaminate its underside, and the
surgeon proceeds with the incision
and dissection toward the foreign body.
During
the dissection, at such times as he wants help, the surgeon holds the
end of a forceps
directly over the point where he believes the foreign body to lie, and
the protecting velum, its
underside still sterile, is turned down over the wound, the red light
is again extinguished, and the
radiologist corrects the position of the surgeon's forceps by directing
him to move it to the right or
the
261
left, until the correct
spot is found. The surgeon has only to work directly downward to come
upon
the object of his search.
It
will be unnecessary in many cases to expose the foreign body completely
by dissection;
often it is only necessary to determine its approximate anatomical
position, especially when it lies
in the depth of a muscle. Frequently it will be possible, after making
a small skin incision, to
extinguish the red light, turn on the X-ray current, and under
fluoroscopic guidance insinuate the
end of a closed, narrow-jawed, blunt forceps into the tissues until it
touches and moves the foreign
body. With the X-ray current still on, the jaws of the forceps are
separated, the foreign body
grasped and extracted. The red light or the ordinary brilliant white
light of the room is then turned
on, and the remainder of the operation conducted in the usual manner.
In some situations it will be
possible to turn a jagged projectile so that the extraction forceps
will seize it by its sharp or jagged
edge or point. A needle may be grasped near one end. One who has not
gained experience in this
method of extraction can not appreciate the ease with which a foreign
body may be secured and
removed in this manner. In a series of several hundred extractions
performed in this way, the writer
has never been longer than 20 minutes, usually much less, from skin
puncture to extraction of
foreign body, and only twice has he failed to remove the foreign body.
Both failures were in cases
in which hypodermic needles were broken off deep in tissues too thick
to be easily studied with the
fluoroscope.
Protection of both the patient and the operator from
an
overexposure of X-rays is of
first importance. It goes without saying that the usual lead lining of
the X-ray tube holder protects
the patient and the operator from all rays except those illuminating
the spot upon the fluoroscopic
screen. This field of radiation should be kept as small as possible and
nothing but the forceps of the
operator should ever enter it while the current is on; sufficiently
long forceps should be employed
to keep the hands out of the direct rays. Protection of the patient and
additional security for the
operator is afforded by placing over the tube a filter of at least 2
mm. of aluminum, and by reducing
to a minimum the time required for the X-ray observations. Onlookers
not directly interested should
not prolong the operation by participating in the screen work. The
method is entirely safe if
reasonable care is taken to minimize the time of X-ray observations. If
the eyes have been properly
prepared by a preliminary stay in obscurity, 1 or 2 milliamperes of
current will suffice. A foot
switch is essential. The X-ray current should be off every second the
observer's eyes are not intent
studying the screen. During early experiences, the X-ray current may be
turned on and off twenty or
thirty times during the operation; but after the first few cases the
extraction will be accomplished
during a very few moments.
BONNET METHOD
The
bonnet procedure has the advantage over the foregoing method that it
can be carried out
in the operating room in the usual light by which the surgeon operates.
The
requirements are an ordinary fluoroscopic horizontal table, or a
makeshift; a
fluoroscopic bonnet; and a sighting needle or pointer sufficiently
262
long to permit the hand
holding it to remain outside of the zone of active X rays.
The
United States Army bedside unit, which is now being adapted to general
practice,
affords a very convenient instrument for taking the X-ray apparatus to
the operating room,
providing the surgeon does not wish to take his patient to the X-ray
room. An ordinary massage or
nonmetallic table or a stretcher will serve the purpose. The
tube-holding arm and tube of the bedside unit is placed under the
table, approximately under the foreign body when the patient is in
the position for operation. No effort need be made to hide the glow of
the X-ray tube, as this type
of X-ray operation can be carried on in the most brilliant light needed
for operating purposes.
A
fluoroscopic bonnet, or, in its absence, a hand fluoroscope of the
ordinary type, will be
needed. In the latter instance, it will be necessary to provide the
radiologist with a pair of smoked
spectacles. The bonnet fluoroscope, especially Dessane's, is much
simpler and more convenient.
As soon as the radiologist finishes his observation, the lower part of
the bonnet is turned up and
held in this position by springs, while a shutter of smoked glass comes
down automatically in front
of his eyes (fig. 156). The position of the hood thus lifted eases the
weight and materially lessens
the inconvenience of its use. The screen in this form of fluoroscope
measures 13 by 18 cm., an area
much larger than the illuminated field should ever be. For a pointer or
sighting device, an ordinary
urethral sound or a long forceps may be used, if a special localizing
pointer is not provided.
The
radiologist must put on the bonnet or a pair of smoked glasses 12 or 15
minutes before
be will be needed, unless he is already engaged in fluoroscopic work,
so that when called he has
only to don the bonnet and step to the operating room.
For
anesthesia in these cases, when a local anesthetic is not suitable,
nitrous oxide gas is
preferable since it is nonexplosive. The danger of an explosion of
either vapor, however, has, in the
writer's opinion, been considerably overestimated. Ile has seen only
one case and in this no harm at
all was done as the flame was instantly smothered. The danger, of
course, is greater with the open
drop method than with some form of rebreathing anesthetic device. The
Ombrédanne anesthetic
mask is very satisfactory for this purpose.
After
the patient has been made ready for operation in the position in which
the localization
was done, the protective sterile velum is placed over him in the manner
already described. When
the surgeon is ready, the radiologist indicates through the sterile
velum, by means of a pointer, the
exact spot on the skin which lies vertically above the foreign body.
While he holds the pointer in
place the velum is lifted on the side next the surgeon, who places the
end of a sterile forceps on the
skin in the position shown by the radiologist's pointer. The bonnet and
velum are lifted out of the
way, the surgeon notes carefully the point indicated on the skin and
cuts down vertically upon it to
find the foreign body. If he does not find it at the depth he supposes
to be correct, he ties the
bleeding points in order to clear the field of haemostats, and asks to
be shown again the spot where
the vertical ray corresponding to the projectile passes through the
wound. This takes but a moment
on the part of
263
the radiologist and is
done as often as required. The surgeon places his sterile pointer in
the wound
as nearly as possible above the exact center of the image of the
foreign body. Correction of the
position of the surgeon's forceps is made by telling him to move to the
left, right, front, or back,
until the correct location has been found. After the extraction
procedure has been completed it will
be advisable to make still another observation to insure that the whole
of the foreign body has been
removed.
This
method will rarely fail except in badly planned operations where an
insurmountable
difficulty of an anatomical or physiological nature has been
overlooked, or where through some
accident it will be necessary to terminate the operation suddenly.
In
the case of recent wounds, the surgeon will often prefer to conduct his
search through the
already existing wound rather than to cut down vertically upon the
foreign body. Here again the
bonnet will afford valuable control. especially if the tube beneath the
table is susceptible of
movement.
The
bonnet method is particularly helpful in cases of old encapsulated
projectiles or foreign
bodies. By using a very small diaphragm aperture the radiologist
employs the bundle of rays
perpendicular to the plane of the table. When the foreign body is
brought into the line of this ray
and the point marked upon the skin perpendicularly over the ray, the
surgeon knows if he dissects
vertically downward he can not fail to find the foreign body.
Ledoux-Lebard and Ombrédanne
have demonstrated the special value of this method in cases of
intra-osseous projectiles.
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