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691
Review [IT-..
..
Gunshot Jeremy
Wounds:
Hollerman,1
J.
Radiologists
Martin
Article
.
2. Radiology
L. Fackler,2
Douglas
M. Coldwell,3
Ben-Menachem4
substantially to the evaluation and a gunshot wound. Plain films, CT, angiography, and sometimes MR imaging are used to localize the missile, determine what path it followed in the body, assess missile and bone fragmentation, and identify missile emboli. If the peritoneal cavity was entered by a bullet, a laparotomy is required. Missiles subject to magnetic forces can complicate MR imaging. Certain locations of missile fragments predispose to lead poisoning or lead arthropathy. Angiography is useful for both diagnosis and treatment. Both angiographic hemostasis and per-
To understand the radiology of gunshot wounds, a basic knowledge of wound ballistics is needed. (See the companion paper, “Bullets, Ballistics, and Mechanisms of Injury,” in this issue.) Useful clinical and forensic information can be derived
cutaneous
Assessment
treatment
can contribute patient with
and Yoram
of the
foreign
body removal
from such
ogist’s
may be used.
Gunshot wounding is an interaction between the penetrating projectile, the anatomy of the wounded subject, and the chance occurrences that determine the exact missile path. The mass and velocity of the projectile establish the upper
knowledge
experience
when
of Missile
On a radiograph,
it is complemented
by the radiol-
in film interpretation.
Type
assessment
of missile
caliber
is difficult
angle between the long axis of the bullet and its path of flight.) The radiologist can contribute substantially to the successful treatment of the patient with a gunshot wound. Important
because of magnification and missile deformation (Fig. 1). If an undeformed bullet is seen in two views at 90#{176},and its degree of magnification is known, it is possible to assess the caliber of the bullet. The focus-object distance and focusimage distance (also known as the focus-film distance) must be known. This requires knowing the position of the bullet in the patient’s body and its location relative to the film [1]. Many radiographs show only fragments of the bullet and do not allow determination of the type of weapon and projectile causing the wound. Certain bullets fragment in a characteristic
analysis includes determining the missile path by using plain films, CT, and sometimes MR imaging. The radiologist further evaluates the extent of wounding by assessing missile and bone fragmentation and by determining secondary missile paths. It is important to identify sites of missile emboli, decide whether missile fragments are intraarticular or intraspinal, and determine whether structures such as large vessels or hollow viscera have been traversed.
grain Remington semijacketed hollow-point bullet). Sometimes the pattern of fragments can be used to identify the bullet. Deformation of large lead shotgun pellets (e.g., 00 buckshot) after contact with bone can cause these to be confused with deformed bullet fragments [2]. Missile caliber is only one indicator of wounding potential, and it is not a very good one. Unfortunately, conventional
limit
of possible
tissue
damage.
Whether
this
potential
is
realized, and where, depends on what tissue the missile encounters, whether the missile fragments or expands, and at what point along the missile path yaw occurs. (Yaw is the
Received December 11, 1989; accepted after revision May 7, 1990. 1 Department of Radiology and Medical Imaging, Hennepin County Address reprint requests to J. J. Hollerman. Ballistics Laboratory, Military Trauma Research, Letterman 3Department
of Radiology, of Radiology,
AJR 155:691-702,
October
University University
of Washington of Washington,
1990 0361 -803x/90/1
Medical Army
pattern
Center Institute
School of Medicine, Seattle, Harborview Medical Center,
554-0691
C American
Roentgen
(e.g.,
and University of Research,
Ml 6 military
of Minnesota, San Francisco,
WA 98105. 325 Ninth Ave. (ZA-65), Ray Society
Seattle,
bullets
701
and the .357 magnum
Park
CA 94129. WA 98104.
Ave.
S., Minneapolis,
125-
MN 55415.
HOLLERMAN
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ET AL.
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1990
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Ii
Fig. 1.-A and B, Radiograph (A) and photograph (B) of same six rounds (A-F) at three different distances from the X-ray film. A = .30-06 (the version of this round with a full-metal-jacket bullet was the military round of the United States in World Wars I and II), B = .25-35, C = .38 special, D = .357 magnum, E = .22 long rifle, and F = .22 short. In A, In left column, focus-image distance (FID) (also known as focus-film distance) is 40 in. (101.6 cm), and focus-object distance (FOD) is also 40 in. (101.6 cm). In center column FID and FOD are 40 in. (101.6 cm) and 35 in. (88.9 cm), respectively (14% diameter magnification). In right column, FID and FOD are 40 in. (101.6 cm) and 30 in. (76.2 cm), respectively (33% diameter magnification). Note that visual impression is of much greater magnification, probably because of visual perception of area rather than diameter. Depending on bullet’s position in body of wounded subject, there is a differing degree of magnification of bullet on radiograph. FOD changes with changes in the patient’s position. As would be expected, with increasing magnification, sharpness of margins of bullet decreases slightiy. Degree of bullet deformation in each projection influences measured diameter. Because of magnification and deformation, reliable assessment of caliber can be difficult. (Figure courtesy of Bradford Allan and Larry Algiers.)
weapon
Localization
diameter
As in all of radiology, localization requires two views at 90#{176}, or a tomographic image. CT of the head and body is often useful for analysis of bullet path. The CT digital scout radiograph can be used for missile localization. It usually can be
and bullet designations are often numerically incorrect. In Figure 1 , note that the .38 special (labeled C) and the .357 magnum (labeled D) use bullets that have the same
(.357 in. [9.07 mm]). These bullets are often exactly
the same weight. The longer cartridge case of the magnum contains more powder, giving the bullet higher velocity and greater wounding potential. These two bullets do not look
exactly alike because the .38 special is a standard lead bullet, and the squared-off .357 magnum bullet is a semiwadcutter shape. Either bullet could be put in either case. Note how much room for powder there is in the cartridge case of the .30-06 hunting rifle round (the nomenclature refers to a .30
caliber bullet modified in 1906) at the top of each column (labeled A). This round, loaded with a soft-point or hollowpoint civilian bullet, is far more likely to cause a severe wound than standard military or assault rifle ammunition. A jacket made of a metal harder than lead, such as copper
or a copper the lead core
alloy, is used to completely
or partially
of many
bullets.
If a bullet
eted, the bullet jacket
usually
cannot
the lead core on standard bullet is of metallic density.
or fragments, is visible
radiographs, Occasionally,
the bullet jacket
separates
surround
is fully or semijack-
be distinguished
from
because the entire as the bullet deforms
from the bullet and
of Missiles
taken in anteroposterior ing the patient.
and lateral projections
The ability
and level allows visualization
to manipulate
without
the display
of bullets through
mov-
window
dense struc-
tures, such as the shoulders and pelvis. It always must be ascertained that the path from the entrance wound is consistent with the bullet’s current location, because a bullet may have reached its present location by embolization. Even in the absence of embolization, bullets, particularly handgun bullets, do not always follow a straight path in the body. They may ricochet off of body structures, especially bone (Fig. 2), or may follow fascial or tissue planes [4, 5]. However, most bullets do follow fairly straight paths through the body (Fig. 3). Bullets that are deflected by anatomic structures, or that follow tissue planes, tend to be traveling at low velocity (less than 1100 ft/sec [335 m/sec]) (Fig. 2). Bullet shape also influences the tendency to be
deflected.
on a radiograph.
When an undeformed
bullet is seen on a radiograph,
it is
usually not possible to state accurately whether it is fully jacketed or not. It may not have deformed because it entered the patient with insufficient velocity, it did not strike a structure causing it to deform, or it is a full-metal-jacket bullet. Some full-metal-jacket bullets, such as that fired by the Ml 6 military rifle, do fragment on short-range shots [3], but most do not.
Missile
Embolization
In general, bullet and missile fragments that embolize were fired from common handguns or .22 caliber rimfire rifles and entered the body at low velocity [6-8]. Often, they are nearly spent, having the ability to penetrate only one wall of a tubular structure (therefore becoming contained within it).
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AJR:155,
October1990
RADIOLOGY
OF
D
GUNSHOT
693
WOUNDS
E
Fig. 2.-Unpredictability of wound path In a bullet wound caused by a handgun. Patient, who had previously undergone coronary bypass surgery, was shot with a .22 caliber handgun bullet, which travels less than 1000 ft/sec (305 rn/see). A and B, Posteroanterior(A) and lateral(B) chest radlographs. Imaginary straight line from entry wound (arrow) to bullet’s resting point was not bullet’s path. This is shown by anglographic findings (C, D). C, Aortogram shows bullet was deflected anteriorly and skidded along inner aspect of anterior chest wall from left to right. Bullet caused transection and false aneurysm of left internal mammary artery (M) and was deflected again by sternum, posteriorly toward center of right hemithorax, causing Injury to origin of native right coronary artery, seen bleeding (arrow) through a channel in right atrloventrlcular septum Into right atrium (A) and right ventricle (V) simultaneously. Black arrowheads mark patent coronary artery bypass grafts. D and E, After cardiologist’s evaluation showed volume of coronary artery bleeding did not require thoracotomy, embolization was performed angiographically. Anglograms of left internal mammary artery obtained before (D) and after (E) embolization for pseudoaneurysm of Internal mammary artery (arrow in D), are shown. (Occluding agents: a steel coil backed by one Gelfoarn torpedo (Upjohn Co., Kalamazoo, Ml]).
Arterial and venous embolization of bullets and shotgun pellets, as well as bullet movement within the spinal canal subarachnoid space, has been reported [6-1 1 ]. A bullet em-
bolus in the right or left pulmonary
artery may shift from one
pulmonary artery to the other as the patient changes body position [6]. Migrating venous bullets are more likely to lodge in the right ventricle than in the pulmonary arterial tree because they tend to become trapped beneath the tricuspid valve or within the chordae tendineae [6]. Although rare, paradoxical embolization can occur, originating in the venous system and passing through a patent foramen ovale, presenting as a distal arterial embolus.
Occasionally, a missile may traverse one wall of the gastrointestinal tract or tracheobronchial tree and subsequently
pass out through It is generally
these [1 2, 13]. accepted
that
a missile
freely
floating
within
a cardiac chamber should be removed to prevent embolization [14, 15]. Missiles clearly embedded in chamber walls are relatively safe [14]. In one case, a shotgun pellet was probably dislodged from the heart during cardiopulmonary tion, and embolized to the intracranial circulation,
result
[16].
important,
embolization.
Missile because
size does all sizes
Two-dimensional
not can
seem
resuscitawith a fatal
to be especially
produce
echocardiography
morbidity
after
is useful in
HOLLERMAN
694
ET AL.
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1990
bullets [7, 9, 21 , 22]. Significant deformation of an intravascular bullet is a relative contraindication to retrieval with a transarterial catheter because of potential damage to the intima [8, 23]. Arthroscopy sometimes can be used for re-
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moving
Extremity
bullets from joints, especially
the knee [24].
Wounds
In extremity
wounds,
when
a radiograph
reveals
an unde-
formed bullet lying in the soft tissues and no fracture is present, tissue disruption is usually minor (Fig. 4A). However, if a major vessel or nerve is divided, can have a severe effect. If a cluster of small bullet fragments
graph this is a strong at that site [25].
temporary
Fig. 3.-Accidental self-shooting (holster accident, .44 hollow point). Bullet entered at midline of popliteal fossa. Wound tract was through superficial and deep posterior and anterior tibial compartments. A and B, Proximal (A) and distal (B) angiograms of right popliteal artery and leg show spasm of posterior tibial (T) and peroneal (P) arteries and an intimal flap in posterior tibial artery (arrowhead). Anterior tibial artery is occluded at mid-calf and is irregular immediately superior to site of occlusion (arrow); it reconstitutes via collaterals above ankle. Surgical inspection of all three arteries is needed and, probably, ligation of anterior tibial artery. Given tricompartmental involvement, multiple fasciotomies may be
required. Operative wounds should be left open.
determining whether a missile is embedded in a chamber wall [1 4]. CT (particularly high-speed CT) and MR imaging for nonmagnetic missiles also have a role. On chest radiographs, blurring of the margins of a pericardiac missile or fragment is grounds for suspecting that the missile is in or next to the heart [1 , 1 5]. If a surgeon reports one hole in the heart at thoracotomy, but no missile is found in the chest during surgery or on chest radiologic studies, a search for an embolized missile should be undertaken. Similarly, if an intrathoracic metallic foreign body is seen on the chest radiograph of a patient without a chest wound, the possibility that this represents an embolus should be considered [6]. Bullets may move within the skull and brain [1 0, 17, 18]. In
the brain, this sometimes
signifies
brain abscess,
or occa-
sionally represents retrograde movement along the wound path of entry [18]. Bullet passage from within the skull into the spinal canal has been described [10]. Whenever a bullet is not found on radiographs of the body part predicted on the basis of the entrance wound to contain it, the bullet’s location is not known, and there is no exit
wound,
additional
radiographs
or fluoroscopy
to find the bullet
is mandatory. Immediately before surgery for removal of a missile, another radiograph should be obtained to confirm the exact location of the missile [7]. Radiolucent plastic bullets exist [19, 20], but injuries from these rarely are seen in the United States. Interventional radiologic techniques are useful in bullet removal, including the removal of intravascular and intrarenal
indicator
Air visible
cavitation
even
a simple
is visible
of significant
between
blunt trauma
muscle
wound
on a radio-
tissue bundles
damage suggests
in that region.
Handgun wounds of the extremities yield characteristic fracture patterns. Frequently seen are divot fractures of cortical bone, drill-hole fractures, butterfly fractures, and double butterfly fractures [26-29]. Nondisplaced fracture lines sometimes radiate from these defects. These usually heal well [30]. Unusual spiral fractures proximal or distal to the bony gunshot wound also occur, probably because of stress risers
and the fact that the bone was under load or stress time of impact
[27, 29]. Early fasciotomy
ment syndrome
is important,
In gunshot fractures from greater extent of comminution
to prevent
at the
compart-
when needed. rifles and large may be seen
handguns, a [26, 28, 31].
These fractures often have complications because of the softtissue damage these bullets cause [28]. Wound infections are more common in this group [28]. At some hospitals, outpatient treatment is being used successfully for extremity fractures caused by handguns, if no significant neurologic or vascular compromise has occurred [32].
Lead Fragments Lead fragments
and Lead Poisoning in soft tissue usually become
encapsulated
with fibrous tissue and do not cause problems. Lead intoxication occasionally can result from soft-tissue wounds, particularly those containing many lead pellets [33]. lntraarticular, disk space, and bursal locations of bullet fragments are common for bullet-induced lead poisoning [34-37]. Lead fragments in the brain are usually benign unless they are copper-
plated (as are many civilian .22 caliber bullets) plated lead pellets produced a sterile abscess
[38]. Copperor granuloma
in the brain of cats surgically implanted with missiles of this type [38]. This was often associated with downward migration of the missile, resorption of copper from the surface of the missile, progressive neurologic deficit, and often death. These findings were absent in cats whose brains were implanted with uncoated lead pellets. lntraarticular fragments should be removed to avoid the destructive synovitis that lead can cause [31, 34]. Fragments within a joint space may be distributed by joint mechanics so that they create an arthrogramlike effect on radiographs,
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AJR:155,
October
1990
RADIOLOGY
OF
GUNSHOT
WOUNDS
695
Fig. 4.-Two patients shot with handguns. A, Radiograph shows a small-caliber, handgun bullet that lacked sufficient velocity to exit child’s upper arm. As no hard object (such as bone) stopped the bullet, and it did not traverse any other body part before the arm, bullet had lithe wounding potential when it entered patient. Even a missile such as this can produce a serious wound if it divides a major vessel or nerve, similar to a stab wound. One also must make sure that bullet did not arrive here by embolization. B, Radiograph of knee after bullet traversed patella shows bullet fragmentation within joint space has created an arthrogram effect, which has been referred to as a plumbogram. Articular cartilage of lateral compartment of tibiofemoral joint is outlined by fragments.
A
delineating cartilage surfaces and joint capsule recesses (Fig. 4B). This has been termed a plumbogram [39]. Significant damage to the articular cartilage visible at surgery may be present as a result of lead synovitis, when radiographs remain normal except for bullet fragments [34]. If large fragments are present in the joint, they can cause severe mechanical trauma during motion. This motion can cause further lead fragmentation. Lead is relatively soluble in synovial fluid. Whether lead poisoning occurs depends largely on the surface area of the retained lead particles and their location in the body [36, 40]. In several cases, a fibrotic mass containing gray fluid with a high lead content has been observed adjacent to the site of the large bullet fragment(s) [35-37]. In cases of lead encephalopathy, CT of the brain may show contrast enhancement in a gyriform pattern [36]. Sometimes the onset of clinical lead poisoning can be quite rapid [40, 41 ], but usually it takes years.
Abdominal
Wounds
In trunk wounds, an analysis of the bullet path to determine whether the peritoneum has been traversed is mandatory. Two radiographs at 90#{176}, CT, clinical examination, and peritoneal lavage are all useful [42]. Abdominal CT is more accurate if performed before peritoneal lavage. If peritoneal penetration by a bullet is suspected, laparotomy is indicated [43-45]. The morbidity and mortality rates of an exploratory laparotomy that shows no significant intraabdominal injury are low compared with those of missed intestinal injury. CT is useful, especially when an exclusively body-wall or retroperitoneal path is suspected [46,47]. CT has largely replaced excretory urography as the preferred means of evaluating the urinary tract after penetrating trauma. Excretory urography is not very sensitive for detection of renal injury [48]. During interpretation of posttrauma abdominal CT, the daily challenge remains detection of intestinal injuries. CT examination of metal fragment or war injuries is difficult because
B
the presence of oral contrast material can mask intraluminal metallic fragments, but without oral contrast material, through-and-through gastrointestinal injuries may be missed [49]. The entire body wall always must be included on the CT display of any patient injured by fragments [46].
Chest
Wounds
Any bullet wound below the nipple line should raise the question of whether the diaphragm or abdomen has been penetrated. CT sometimes can be used to make this determination [49]. Laparotomy is required if peritoneal penetration cannot be excluded [44, 50]. Only 1 5-20% of urban gunshot wounds to the chest require open thoracotomy [51 ]. Chest wounds are often treated adequately with tube thoracostomy, airway management, and, if necessary, blood replacement. Clinical examination, analysis of drainage material from the chest tube, and examination of the chest radiograph will determine whether the patient needs a thoracotomy. Whenever a gunshot wound traverses the midline of the neck or the width of the mediastinum, perforation of the esophagus should be suspected [52]. Esophageal evaluation should not be overlooked after angiographic evaluation of the neck or chest.
Head
Wounds
Outcome is determined by the specific brain structures wounded. CT is effective for detecting bullet and bone fragments but is less accurate for detecting wood, clothing, plastic, stones, and other relatively radiolucent material propelled into the wound by the bullet. Inward beveling of the calvarial defect at the bullet entrance and outward beveling of the skull at the exit wound are typical [53-57]. This is due partly to the geometry of the skull [57]
HOLLERMAN
696
and partly to the bullet-bone interaction. Characteristic ture patterns of the skull can be used to identify entrance
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exit wounds
[5, 53-56].
fracand
When there is a cranial exit wound,
fractures propagate across the calvarium faster than the bullet travels through the brain, producing characteristic patterns of fracture sometimes allowing differentiation of entrance and exit [53, 54]. Bullets crossing the midline of the brain either sagittally or coronally are usually lethal [58-60]. The presence of bone or metal fragments away from the path of the largest bullet fragment is associated with a poor prognosis [59]. Selfinflicted gunshot wounds are more frequently lethal than gunshot wounds sustained during an assault [59, 60]. This is probably because of the usual coronal bullet path of selfinflicted injuries, across the midline and near the brainstem. Approximately 2% of gunshot suicides involve multiple wounds, usually when the first wounds are not disabling [1].
As in the rest of the body, because of the skin’s elastic properties, a nearly spent bullet is often arrested subcutaneously
at the end of the wound
Pellet
Wounds
path.
Compared with the pointed rifle bullet, the spherical pellet slows rapidly in its flight through air or tissue [61]. In tissue, the entire wounding potential of the shot pellet at its entrance velocity is likely to be delivered to the target, often with no exit wound. Victims hit by multiple projectiles must be assessed in light of the combined wounding capacity of the projectiles. This is particularly important in shotgun wounds
and is sometimes
important
in analysis
of multiple
bullet or
fragment
ET AL.
blood
AJR:155,
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to tissue
between
the wound
October
channels
1990
(Fig. 5).
The most severe civilian firearm wounds typically seen are those inflicted by a shotgun from close range [62, 63]. After a close-range or contact shotgun wound to the trunk, external examination of the patient, resuscitation, often does internal injuries present.
particularly after adequate not disclose the severity
volume of the
Diagnosing long-range injury on the basis of the pattern of pellet spread is sometimes problematic. When shotgun pellets are tightly clustered (or widely spread out) close-range (or long-range)
injury
is usually
suspected.
However,
in close-
range injuries, the “billiard ball” effect may cause considerable pellet spread [1]. On radiographs, particularly in trunk wounds, this effect can simulate the pellet spread of a longerrange injury [1 , 63]. When shotgun pellets are clumped, particularly in the lower abdomen, they may be in a hollow viscus, such as the bladder
or intestine
[64]. The inherent
elasticity
and contraction
of the
highly muscular bladder wall can seal off puncture wounds of 0.5 cm or less [64]. Therefore, sometimes after bladder penetration, no leak is seen on the cystogram. Preoperative angiography of most close-range shotgun ex-
tremity wounds is recommended [65, 66]. Major neural injury after shotgun wounding may be more important than fracture or major vascular injury in determining the final outcome [67]. During surgical exploration it is important to conduct
column,
of a close-range a careful search
shotgun wound, for wadding, wad
casing debris, plastic shot cup, and surface materials
carried into the wound (e.g., clothing, glass, or wood). Many of these are radiolucent. Newer BB guns and airguns that fire small pellets have considerably higher muzzle velocity (up to 300 m/sec) than
wounds, particularly those fired in rapid bursts that strike the body nearly simultaneously. At close range (