Although bullets are not sterilized on discharge, most low-velocity gunshot wounds can be safely treated nonoperatively with local wound care and outpa-tient management.. At an inner-ci
Trang 1Over the past century, 223 million
guns have been introduced into this
country, including 77 million
hand-guns, 66 million shothand-guns, and 79
million rifles (3 million of the
assault type).1,2 The presence of a
firearm, now estimated to exist in
half of all US households,2 increases
an individualÕs risk of killing or being killed by threefold and of dying by suicide by fivefold.3,4 Two thirds of these weapons are loaded and stored within reach of a child.2 This environment results in
150,000 to 500,000 missile injuries (half involving the extremities)5and 40,000 to 50,000 deaths annually.4-6 Having increased fourfold since the 1950s, the latter figure approxi-mates the number of Americans lost during the Vietnam War, is nearly twice the number of persons who die of acquired immunodefi-ciency syndrome each year, and is three times the number of deaths associated with drunk driving Gunshot wounds, including acci-dental, intentional, and self-inflicted injuries, are now the second leading cause of death and injury for the youth of this country, especially African-Americans, killing more teenage boys than all natural causes combined.3,4 The homicide rate for males aged 15 to 24 in the United States is roughly 20 times higher
Dr Bartlett is Assistant Clinical Professor of Orthopaedic Surgery, University of Vermont College of Medicine, Burlington Dr Helfet is Director of the Orthopaedic Trauma Service, The Hospital for Special Surgery, New York.
Dr Hausman is Chief of The Hand Service, Mount Sinai Medical Center, New York Dr Strauss is Chief of Trauma, Mount Sinai Medical Center, New York.
Reprint requests: Dr Bartlett, University of Vermont, McClure Musculoskeletal Research Center, 440 Stafford Hall, Burlington, VT 05405-0084.
Copyright 2000 by the American Academy of Orthopaedic Surgeons.
Abstract
As a result of the increasing number of weapons in this country, as many as
500,000 missile wounds occur annually, resulting in 50,000 deaths, significant
morbidity, and striking socioeconomic costs Wounds are generally classified as
low-velocity (less than 2,000 ft/sec) or high-velocity (more than 2,000 ft/sec).
However, these terms can be misleading; more important than velocity is the
efficiency of energy transfer, which is dependent on the physical characteristics
of the projectile, as well as kinetic energy, stability, entrance profile and path
traveled through the body, and the biologic characteristics of the tissues injured.
Although bullets are not sterilized on discharge, most low-velocity gunshot
wounds can be safely treated nonoperatively with local wound care and
outpa-tient management Typically, associated fractures are treated according to
accepted protocols for each area of injury Treatment of low-velocity, low-energy
fractures is generally dictated by the osseous injuries, as these are similar in
many regards to closed fractures Soft tissues play a more critical role in
high-velocity and shotgun fractures, which are essentially open injuries Aside from
perioperative prophylaxis, antibiotics are probably required only for grossly
contaminated wounds; however, because contamination is not always apparent,
most authors still recommend routine prophylaxis High-energy injuries and
grossly contaminated wounds mandate aggressive irrigation and debridement,
including a thorough search for foreign material Open fracture protocols
including external fixation or intramedullary nailing and intravenous
antibiot-ic therapy for 48 to 72 hours should be instituted If there is vascular damage,
exploration and repair are best performed after prompt fracture stabilization.
Evaluation of the Òfour CsÓÑcolor, consistency, contractility, and capacity to
bleedÑprovides valuable information regarding the viability of muscle Skin
grafting is preferable when tension is required for wound closure, although
other soft-tissue procedures, such as use of local rotation flaps or free tissue
transfer, may be necessary, especially for shotgun wounds Distal neurologic
deficit alone is not an indication for exploration, as it often resolves without
surgical intervention.
J Am Acad Orthop Surg 2000;8:21-36 Effects on Musculoskeletal Tissues
Craig S Bartlett, MD, David L Helfet, MD, Michael R Hausman, MD, and Elton Strauss, MD
Trang 2than that in other industrialized
nations.3
The economic impact of gunshot
trauma is also high At an
inner-city hospital, annual costs for the
treatment of these injuries can easily
reach $50 million.3 Nationwide, the
calculated costs of medical
treat-ment, mental health care,
emer-gency transport, police services,
and insurance administration
ex-ceed $2.7 billion annually,5most of
which is borne by American
tax-payers.4,6 These figures do not
include the costs related to
addi-tional loss of productivity, the
attendant pain and suffering, and
the reduced quality of life, estimated
at $63.4 billion each year.5 For
every gunshot homicide there are
3.3 nonfatal injuries.3,5 One of these
will be a brain or spinal cord injury,
leading to lifetime expenditures in
excess of $3 million.3 Because
gun-shot trauma exacts such an
enor-mous toll from both the individual
and society, the surgeon should
take an active interest in both its
prevention and its treatment An
understanding of ballistics and the
wounding characteristics of various
weapons will also facilitate proper
evaluation and care
Ballistics
By convention, bullet wounds are
generally classified as low- or
high-velocity injuries Low-high-velocity
wounds (Fig 1) are less severe, are
more common in the civilian
popu-lation, and are typically attributed
to projectiles with muzzle velocities
below 1,000 to 2,000 feet per second
(fps) Tissue damage is usually more
substantial with higher-velocity
(greater than 2,000 to 3,000 fps)
mil-itary and hunting weapons While
convenient, the terms Òlow-velocityÓ
and Òhigh-velocityÓ can be very
misleading.7,8 Shotguns, for
exam-ple, are technically low-velocity
weapons, but are responsible for
substantial rates of major soft-tissue, nerve, vascular, bone, and joint in-jury,6,9,10 resulting in a mortality rate nearly twice that attributable to other weapons More appropriate are the designations Òlow-energyÓ and Òhigh-energy,Ó which are de-scriptive of the amount of damage
to the tissues To appreciate this distinction, the factors that affect the transmission of the wounding capacity of a missile to the tissues must be considered
Pulling the trigger of a firearm releases its firing pin, which strikes the primer When crushed, the primer ignites, producing an in-tense flame, which enters the main chamber of the cartridge case and ignites the powder The ensuing generation of a large quantity of gas and heat (up to 5,200¡F) pro-duces a pressure as great as 25 tons per square foot, which ejects the bullet.11 Next, the gases trapped in the bore (the evenly hollowed-out inner portion of the barrel) expand and reach a velocity greater than that of the projectile, further accel-erating and destabilizing it for a short distance.12
The wounding capability of the bullet is directly related to its ki-netic energy, determined by the formula E = M/2 ×V2, where E rep-resents energy; M, mass; and V, velocity Before World War II, bullet and weapon construction focused on mass, favoring heavier projectiles of large caliber (diame-ter of the bullet or rifle bore in millimeters or as a decimal frac-tion of an inch) However, in-creasing mass only produces lin-ear increases in kinetic energy, but increasing velocity does so expo-nentially In fact, at the speed of sound (4,760 fps), the rate of
ener-gy conversion into mechanical disruption of tissue can become proportional to the third power of velocity or even higher.13 There-fore, over the past five decades, greater emphasis has been placed
on lighter, spin-stabilized missiles traveling at high velocities The inertia of a projectile acts through its center of mass, which lies along its line of flight.12 Re-tarding forces act at the center of pressure, which lies in front of the center of mass (tip of the bullet) in
a nose-on flight Any degree of deviation of the longitudinal axis of the bullet from its line of flight is known as yaw, the square of which proportionally affects its rate of deceleration.12 The nonspinning bullet is inherently unstable and will have a propensity to tumble
To best minimize this occurrence and achieve gyroscopic stability,
Figure 1 Anteroposterior (AP) view of the right humerus of a 29-year-old man after a small-caliber, low-velocity gunshot wound with resultant radial nerve neu-rapraxia Initial treatment included a coap-tation splint and discharge home on a regi-men of oral antibiotics At 3 weeks, the plaster splint was replaced by a Sarmiento brace, in which uneventful healing was completed The nerve palsy slowly re-solved over the ensuing 4 months.
Trang 3the bullet should be long, thin, and
spun on its axis by helical grooves
in the bore of the firearm (barrel
rifling).12-14 The highly complex
action of spin on a yawing bullet
(precession), combined with a
sec-ond complicated motion of higher
frequency and lower amplitude
(nutation), will cause the missile to
rotate in a rosette pattern of
mo-tion, (analogous to a spinning top),
imparting stability.12
More important than velocity is
the efficiency of energy
trans-fer,8,10,11,13,14which is dependent on
six factors: (1) The amount of kinetic
energy possessed by the projectile
at the time of impact, such that the
longer the range (distance from the
target), the lower the velocity at
impact.13 (2) The stability and
entrance profile of the projectile At
a yaw of 90 degrees (sideways),
max-imal energy transfer is achieved.8,14
Yaw tends to decrease over longer
distances,12 allowing the bullet to
hit its target nose-on; at impact,
however, wobbling and then
tum-bling occur (3) The caliber,
con-struction, and configuration of the
bullet, which can be by far the most
important factors predicting its
effects.7,11,13 (4) The distance and
path traveled within the body
Penetrating (not exiting) missiles
deliver their total contained kinetic
energy; perforating (exiting)
mis-siles transfer significantly less.11,12
(5) The biologic characteristics of
the tissues impacted.11,15 (6) The
mechanism of tissue disruption
(e.g., stretching, tearing, crushing).7
On the basis of the interactions
between these many factors,
differ-ent injury patterns will occur or
even coexist Inefficient energy
transfer by a high-velocity bullet
might produce only minimal
dam-age In contrast, complete release
of energy by a low-velocity
projec-tile can inflict devastating wounds
Thus, Cooper and Ryan14 have
warned that one should Òtreat the
wound [and] not the weapon.Ó
Weapons and Ammunition
Although handguns are typically low-energy weapons, with muzzle velocities below 1,400 fps,11,13they are still the most frequently used firearms in fatal injuries.1,5 Exam-ples include the 38-caliber revolver (600 to 870 fps), the 9-mm pistol, and the 45-caliber semiautomatic weapon (860 fps) A small-caliber short-barreled type, common in urban areas and costing less than
$50, is the ÒSaturday Night Special.Ó Named for their rifled barrel, rifles include low-velocity types, such as the rarely fatal air rifle11,13 and the 22 (1,100 to 1,255 fps).11,13 Higher-velocity military (assault) rifles include the M-16 (3,250 fps)11 and the AK-47 (2,340 fps).7 Even at
300 yd, bullets fired from these par-ticular weapons retain nearly half of their original muzzle velocity
Although the M-16 round has ap-proximately the same caliber and weight as the 22, it is fired at a velocity three times greater than that
of the latter, producing nearly ten times the amount of kinetic energy (Fig 2) Assault rifles have been involved in 16% of homicides in New York City but fewer than 2% of homicides in more rural areas.1 More common in rural areas, shotguns fire a Òmissile,Ó consisting
of a few to hundreds of lead pellets,
at a velocity of 1,000 to 1,500 fps.13 Because of its high efficacy of energy transfer at close-range, the shotgun
is the most formidable and destruc-tive of all small arms A sawed-off shotgun offers the advantage of concealment and more rapid dis-persion of pellets, increasing the probability of striking the target.6,13 Damage is based on the choke, load, barrel length (federal law requires a minimum of 18 inches), smooth bore, wadding, powder charge, and range.6,16 The choke is
a partial constriction of the bore at the muzzle that condenses and con-trols the shot pattern The tighter
the choke, the smaller the spread of pellets and the greater the length of the shot column ÒGauge,Ó which refers to the number of lead balls of the given bore diameter that are required to weigh 1 lb, is an archaic term.11 The load is composed of different sizes of shot, packed into what is usually a plastic shell The role of wadding is to fill up dead space in the shell, protect the pow-der and shot, and seal the bore dur-ing firdur-ing to keep gas behind the pellets.11 It is commercially pro-duced from paper, cardboard, felt, plastic, or composite materials The quantity and type of gun-powder affect the initial kinetic
ener-gy of the bullet Gunpowder (black powder) was originally composed of
a mixture of saltpeter (potassium nitrate), charcoal, and sulfur and was measured in drams Modern smokeless powder, invented in 1884 and modified much since then, is measured in dram-equivalents.11,16
Figure 2 AP view of the right distal femur of an 18-year-old woman with a high-velocity M-16 rifle wound Note the Òlead snowstormÓ pattern and severe com-minution The arteriogram revealed no gross arterial damage.
Trang 4Bullets are composed primarily
of lead combined with varying
amounts of other metals
depend-ing on their desired final hardness
(0.5% antimony, 0.3% copper, and
0.05% other metals in one common
formulation).17 They can be
modi-fied in many ways to improve
energy transference, including full
or partial (soft-point) metal
jacket-ing, partial metal jacketing with a
cavity at the tip (hollow point),
controlling expansion with use of
aluminum, scoring, bonding,
com-bining multiple projectiles into
one cartridge, and adding an
explosive charge.7,11,14,18 The
com-mon failure of explosive bullets to
detonate on impact presents
con-tinuing danger to both medical
personnel and patients Magnum
shells and cartridges contain a
heavier than standard powder
charge, which increases projectile
energy by 20% to 60%.6 Scoring
the bullet (e.g., the dumdum)
makes it more likely to fragment
when subjected to strong in-flight
physical forces.13,18 A bullet
com-posed of bonded fragments of iron
or lead (e.g., 22-caliber frangible)
will disintegrate on striking a hard
surface
Fully jacketed bullets are
uti-lized primarily in assault rifles
These have a lead or steel core,
which is covered by an outer jacket
of cupronickel or gilding metal
(copper or zinc) to minimize
defor-mation Therefore, they invariably
exit the victim if he is the primary
target within a few hundred yards
of the muzzle In contrast, both
soft-nose and hollow-point bullets
flatten out on impact, the latter
expanding up to twice their
origi-nal diameter and quadrupling the
amount of tissue struck.7 At high
velocities, these bullets also shed as
they travel through the body,
creat-ing a characteristic radiographic
Òlead splatterÓ or Òlead snowstormÓ
pattern11(Fig 2) Most hunting
bullets also exit the body.11
Shot shells are handgun car-tridges with bird shot encased in plastic The plastic contains the shot until impact, often producing fatal results at distances of less than
10 ft.11,18 In contrast, a shotgun slug (a single large projectile mounted into a shotgun shell) can produce massive internal injuries compara-ble in severity to those of high-velocity rifle bullets
The Bullet Wound
An impact velocity of only 150 to
170 fps is required to penetrate skin.6,12 Most entrance wounds, regardless of range, are oval to cir-cular with a punched-out clean appearance and are often sur-rounded by a zone of reddish dam-aged skin (the abrasion ring).11 While powder tattooing of the skin implies a close-range wound, the fact that there are different forms of propellant powder makes this an unreliable finding Also indicative
of a close-range injury is a cherry-hue appearance of underlying muscle due to carboxyhemoglobin, formed by carbon monoxide re-lease during combustion.11
Damage is created by several mechanisms, including the actual passage of the missile through tis-sue, a secondary shock wave, and cavitation On striking its target, the bullet creates a temporary
cavi-ty at the entry site due to stretching forces and the vacuum created by its passing The volume of this cav-ity is proportional to the energy transferred by the missile (Fig 3)12;
a maximum size of 10 to 40 times the diameter of the bullet is reached
in 1 to 4 msec,11,13,19,20with internal pressures reaching 100 to 200 atm.20 This violent event in high-velocity injuries over 2,500 fps can create damage of an almost explosive nature.12
During the 10- to 30-msec life-time of the temporary cavity,20its
vacuum may pull foreign material into the wound.12,13 However, most bullets are pointed and transfer little from the entry site.14 A Òtail splashÓ
or Òsplash backÓ effect at high velo-cities can cause backward hurling of injured tissue.8,11,20 After the bullet passes, the temporary cavity col-lapses and re-forms repeatedly with diminishing amplitude, leaving a smaller permanent cavity.13,20 The more the elastic capacity of the sur-rounding tissue has been exceeded, the greater the size of this perma-nent cavity
Wang et al15separate the wound area into three zones: (1) a primary wound track (the permanent cavi-ty); (2) a contusion zone of muscle adjacent to the track; and (3) a cussion zone (variable outside con-gestion) In uncomplicated low-velocity civilian gunshot wounds, this area is essentially only a few cells deep.21 Therefore, these wounds rarely require full explo-ration.22 However, the volume of devitalized muscle grows with increasing energy, becoming
visual-ly apparent at velocities over 1,000 fps and resulting in extensive bruis-ing at velocities over 2,000 fps.8,12 After impact by a high-velocity, rapidly decelerating, deforming, and disintegrating projectile, tissue destruction may extend up to
sever-al centimeters radisever-ally from the track.13 Fascial planes may serve as channels for the dissipation of explosive force, leading to signifi-cant remote tissue damage.14 As a result, disruption of muscle capil-lary blood supply, rupture of gas-containing viscera, and fractures can occur even without a direct im-pact.11,12
Energy loss by the bullet and tis-sue disruption along the wound track are not uniform, due to varia-tions in tissue density and the behavior of the bullet as it travels from one structure to another.15 Soft, bulky, homogeneous solid organs, such as liver, spleen, and
Trang 5muscle (specific gravities of 1.01 to
1.04), are violently disrupted when
transferred kinetic energy exceeds
the elastic limits of the tissue.13,20
Histologically, swelling of muscle
fibers to as much as five times
nor-mal size can be observed, with
clot-ting of muscle cytoplasm, loss of
striations, and interstitial
extravasa-tion of blood Lactate levels increase
to as much as six times normal, and
depletion of adenosine triphosphate,
creatine phosphate, and glycogen
occurs.23 These changes result in
local edema, which may lead to a
compartment syndrome, further
in-creasing the insult to the soft
tissues.7
Bone (specific gravity of 1.11) can
be shattered beyond recognition, but
less dense and more elastic tissues,
such as skin and lung (with much
lower specific gravities of 0.2 to 0.5),
may be virtually unscathed.11,14,20
Although capillaries are prone to
rupture, larger arteries (unless directly struck) are remarkably resis-tant to injury.12 Likewise, larger nerve trunks, while susceptible to neurapraxic lesions, are rarely com-pletely disrupted.12
Exit wounds can appear stellate, slitlike, crescentic, circular, or com-pletely irregular.11 With greater velocities, bullet deformation, and tumbling within the body, these typically become larger and more irregular than entrance wounds.13 For example, a full-metal-jacket bullet will produce a small cylin-drical cavity until it begins to tum-ble When this occurs, massive amounts of kinetic energy are re-leased, widening the cavity and exit wound However, a retro-grade effect can occur if the bullet slows and releases a large amount
of energy immediately after impact (as may occur with rapidly expand-ing huntexpand-ing ammunition) This
will form a track with a cone based
at the entry site.11,13 Thus, contrary
to popular opinion, an exit wound
is not necessarily larger than the corresponding entrance wound In contrast to entrance wounds, cavity formation at the exit site may allow substantial quantities of material to
be sucked into the wound, particu-larly when the velocity exceeds 2,000 fps.11
The Shotgun Wound
Complicated formulas exist to de-termine the range of a shotgun wound However, it may be easily estimated by measuring the diame-ter of the spread on the patient As the shot pellets travel from 2 to 100
yd, they separate slightly less than
1 in/yd.6,16 Soft-tissue shotgun injuries can
be graded from the most extreme (type III) to benign (type 0)6(Fig 4) Type III (Òpoint blankÓ) wounds are due to impact from a range of less than 3 yd and are extensive, with the concentrated cloud of shot potentially destroying everything in its path Wound diameters of 6 in
or less often herald injury to deeper structures.16 The presence of soot is evidence of a blast from a range of 1
ft or less.11 Massive soft-tissue destruction and bacterial contami-nation from wadding require ag-gressive treatment and often long hospital stays Type II (close-range) wounds, due to impact from a range of 9 to 21 ft, are almost as severe and penetrate deep to the fascia These are less likely to have embedded wadding, which tends to fall away after distances greater than 6 ft.6,11
Type II and III wounds are asso-ciated with high rates of commin-uted fractures (32% to 48%), major soft-tissue disruption (43% to 59%), vascular injury (23% to 35%), and peripheral nerve damage (21% to 58%).9,10,24 Furthermore, vascular
A
B
Figure 3 Blocks of gelatin perforated by 30-caliber missiles at less than 1,000 fps (A) and
at 2,800 fps (B) Arrows indicate missile tracks (Reproduced with permission from
Ziperman HH: The management of soft tissue missile wounds in war and peace J Trauma
1961;1:361-367.)
Trang 6and neural injuries frequently coexist,
and multiple injuries are often
pres-ent Such global trauma leads to
amputation rates as great as 20% to
50%10,24and high mortality rates
In injuries from distances greater
than 7 yd, a large cloud composed
of widely scattered missiles
pro-duces many small holes but rarely
major soft-tissue disruption.6 Such
injuries can often be treated simply
as multiple low-velocity wounds6
and are grouped as type I
(long-range), which penetrate to the
sub-cutaneous tissues and deep fascia,
and type 0, which involve only skin
penetration Beyond 20 to 50 yd
(maximal range), the rapidly
decel-erating and poorly shaped
(aerody-namically) spherical pellets create
negligible damage.13
Bone Involvement
Bone is a specialized form of dense connective tissue composed of cal-cium salts embedded in a matrix of collagenous fibers, which is rarely damaged without concomitant muscle injury A minimum velocity
of 195 to 200 fps is necessary for a bullet to breach its cortex.6,20 The clinical and radiographic appear-ance of the entrappear-ance hole is usually
a punched-out round to oval shape with a sharp beveled edge In con-trast, the exit site typically has an excavated, conelike appearance with a variable amount of com-minution.11 Generally, the greater the velocity of the missile, and therefore the greater its contained kinetic energy, the greater the com-minution at both entry and exit sites (Fig 2)
Lower-velocity projectiles can produce many different fracture patterns, either incomplete or com-plete There are three types of incomplete fractures13,25: (1) the Òdrill-holeÓ fracture, which usually occurs through the soft metaphy-seal region of long tubular bones, and is characterized by entrance and exit holes with diameters close
to the diameter of the bullet; (2) the unicortical (ÒdivotÓ) fracture, which involves a portion of bone removed from the main structure and occasionally a nondisplaced fracture line extending from the divot; and (3) the chip fracture, more common in stab wounds and rarely seen after bullet injuries
Complete fractures are more fre-quent in diaphyseal bone and in-clude patterns such as the single and double ÒbutterflyÓ fractures
Their spectrum ranges from frac-tures secondary to indirect forces to highly comminuted patterns On impact, bone fragments are pro-pelled toward the periphery of the temporary cavity Although these can become secondary missiles, causing damage to more distant
structures, more commonly they quickly retract to the parent bone.11 Frequently, other secondary mis-siles include articles of clothing, such as buttons and belt buckles.13 Physeal damage has been noted
in 16% of skeletally immature patients who sustain a gunshot wound.26 This is usually due to di-rect damage as the bullet passes near a growth plate, which is easily noted on initial radiographs How-ever, physeal injury can theoretically occur remote from the site of the wound track, leading to unforeseen growth arrest.27
Joint Involvement and Metal Intoxication
A bullet passing through a joint can damage bone, cartilage, ligaments, and menisci Tornetta and Hui28 noted a 42% incidence of meniscal injury and a 15% incidence of chon-dral damage in knee joints violated
by low-velocity projectiles Articu-lar damage may be crippling, with loss of normal anatomic contours leading to severe posttraumatic degenerative arthritis Contamina-tion by bullet fragments can result
in joint sepsis, rapid chondrolysis, and joint destruction
Lead intoxication (plumbism) can manifest from 2 days to 40 years after a gunshot injury.29 Its most common causes include bullet fragments within a joint space, bone, or (rarely) intervertebral disk.11,22,30 Lead fragments in soft tissues are quickly covered by avascular scar tissue,29 which pre-vents their migration and perhaps uptake by the body However, intra-articular lead dissolves in synovial fluid and may be
deposit-ed in subsynovial tissues, leading
to chronic irritation, arthritis, and (rarely) systemic effects (such as neurotoxicity, anemia, nausea and emesis, abdominal colic, and renal disease) Furthermore, toxicity
6 ft
12 ft
24 ft Figure 4 Diameter of the spread of a shot
column as range increases Top, Type III
(point-blank) pattern Center, Type II
(close-range) pattern Bottom, Type I
(long-range) pattern (Reprinted with
per-mission from DeMuth WE Jr: The
mecha-nism of shotgun wounds J Trauma
1971;219-229.)
Trang 7may rapidly accelerate in the
pres-ence of metabolic disorders,
alco-holism, or acute infection.13 Two
deaths have been reported.11 The
use of chelating agents is the initial
treatment for lead intoxication
Bullet removal is usually
neces-sary.13,29
Copper, another metal common
in firearm projectiles, is also
neuro-toxic.17 However, unlike lead,
cop-per causes considerable local
soft-tissue inflammation, necrosis, and
erosion Nickel can also be
inflam-matory Zinc and aluminum
be-have similarly to lead in the soft
tissues.17
The Wandering Missile
Vascular embolization by bullets,
shot, or fragments occurs in rare
instances.11,13,31,32 The 22-caliber
bullet is the most commonly
in-volved projectile Almost one fifth
of cases involve the neck or upper
extremities.32 Migration of missiles
into the portal system, pericardial
space, spinal cord, kidneys, ureters,
urethra, and lungs has also been
observed.6,31
Contamination and
Infection
Contrary to popular belief, bullets are
not sterilized on discharge.11,12,19,33,34
Furthermore, shotgun wadding has
been associated with a high degree
of wound contamination,10,34
espe-cially in the case of older
ammuni-tion, in which the wadding was
often composed of clostridia-laden
cattle hair and jute, and modern
Òhome loadsÓ created with a variety
of substances Additional sources of
infection include clothing
frag-ments, skin flora, and other
contam-inants Therefore, primary closure
is contraindicated Injuries to the
abdomen or bony pelvis are of
par-ticular concern, because of their
close association with bowel injury, which dramatically increases the risk of sepsis.30
Nonviable muscle, especially in
an anaerobic environment, is an ideal pabulum for the growth of many types of bacteria, especially clostridia.12,13 Following a gunshot wound, the number of aerobes in devitalized muscle has been observed to be 10,000 organisms per gram of tissue at 6 hours and 100,000 at 12 to 24 hours, with the quantity of anaerobes at 6 hours falling within this range.35 There-fore, debridement is optimally per-formed within 6 to 8 hours of injury
However, this timing is inexact due
to the degree of tissue destruction, the presence of shock, and host re-sistance.35
When there is too much devital-ized tissue to be absorbed or too great a bacterial load, the body will attempt to wall off the necrotic mass with a fibrin barrier and expel
it after approximately 10 days.7 However, without access to the outside, this mass will form an abscess Incomplete removal of debris, such as shotgun wadding, can also result in abscess formation and chronic drainage In these cases, imaging of the abscess with contrast material may help locate
any foreign material before explo-ration
Most gunshot wounds are not complicated by infection, but infec-tions by certain pathogens are asso-ciated with increased morbidity Clostridial infection can range from cellulitis to diffuse myonecrosis (gas gangrene) It usually develops over 3 days, but may occur within
6 hours of injury Less commonly, streptococcal infection develops over the course of 3 to 4 days, with systemic reactions not appearing until late Although rare, wound botulism can occur even in
clinical-ly clean wounds, and should be suspected in the presence of bulbar and descending symmetric motor paralysis.36
Assessment
In a study of 16,316 patients with gunshot wounds of the extremities, Ordog et al2 noted a 17% overall incidence of vascular injury based
on positive findings by exploration and/or arteriography However, the presence of a vascular injury is dependent on the location of the wound (Table 1), its severity, and the type of weapon used Such details should be considered when
Table 1 Relationship of Wound Location and Incidence of Vascular Injury *
Location of Wound Incidence of Vascular Injury, %
Medial or posterior upper arm 6-8 Forearm or antecubital fossa 17-22
* Adapted with permission from Ordog GJ, Balasubramanium S, Wasserberger J, Kram
H, Bishop M, Shoemaker W: Extremity gunshot wounds: Part one Identification and
treatment of patients at high risk of vascular injury J Trauma 1994;36:358-368.
Based on correlation with arteriography.
Trang 8attempting to identify the presence
of a potentially limb- or even
life-threatening condition
Most vascular injuries after
pen-etrating trauma are manifested by
ÒhardÓ physical findings, which
permit a rapid and accurate
diagno-sis.2,13,37 These include a pulse
deficit; a cold, lifeless extremity;
cyanosis distal to the wound; a
bruit or thrill; pulsatile or
uncon-trollable bleeding; and a large or
expanding hematoma or
pseudo-aneurysm A progressive neurologic
deficit may signal the presence of
the latter ÒSoftÓ signs of a vascular
injury include a history of
hemor-rhage, hypotension, or a static
neu-rologic deficit Unfortunately, even
after complete arterial disruption, a
weak but palpable pulse might still
be present Accurate pulse
assess-ment of a traumatized limb with
normal perfusion can be hindered
by edema, a hematoma, dressings,
or splints.38
Generally, arteriography is
ex-tremely sensitive, quite specific for
identification of vascular injury, and
useful for surgical planning for
treat-ment of complex wounds (Fig 2).2,13
It is particularly helpful after
shot-gun injuries, because of the frequent
occult vessel damage.6 However,
this imaging modality is expensive,
has inherent risks, and is sensitive
enough to detect occult findings that
may resolve spontaneously.2 Due to
these limitations, arteriography may
ultimately be replaced by
noninva-sive duplex ultrasonography, a
modality just as sensitive but
with-out the associated complications.2,38
When the physical examination
indi-cates the presence of a well-localized
arterial injury, preoperative
arteriog-raphy is unnecessary.2,38 In contrast,
the absence of ÒhardÓ findings of
vascular injury warrants a period of
observation
In addition to appropriate
ex-tremity imaging, it is important to
obtain radiographs one body cavity
above and one body cavity below
any entrance or exit wound.13 Clothing, most wadding, and even some metal jackets may be difficult
to see on plain films, making a care-ful inspection mandatory Clues that suggest the presence of a cloth foreign body include radiographic evidence of an irregular or spurred bullet, a relatively large entrance wound for the estimated caliber and range, and the absence of a frag-ment of the patientÕs clothing at the entrance site.13 Careful evaluation
is also crucial when any metal frag-ments lie in proximity to a joint space Although the presence of joint violation or an intracapsular bullet can usually be determined on the basis of the fracture pattern, the plain-radiographic appearance, and the results of joint aspiration (if nec-essary), the most sensitive test remains a fluoroscopically assisted arthrogram.39 If this is impractical
or inconclusive, a computed tomo-graphic scan should be obtained
There are several important med-icolegal issues that pertain to evalu-ation and treatment Care must be taken to preserve evidence by cut-ting aroundÑnot throughÑbullet holes in the patientÕs clothing The location, size, shape, and nature of both the entrance and exit wounds must be precisely documented
Medical teams have often been inat-tentive on this point, with one study noting that fewer than 3% of charts have an adequate description of the wound.7 Bullets should be marked only on the nose or base to preserve the rifling characteristics, and any wadding or loose pellets should be retained for evidentiary purposes.11 Electrodiagnostic studies in the early postinjury period cannot dis-tinguish between a neurapraxic lesion and transection Follow-up studies at 6 weeks and 3 months can show signs of early recovery, but their utility is limited.24,40 The presence of spontaneous fibrilla-tions and muscle irritability is a sign of muscle denervation,
indi-cating axonal disruption In
gener-al, expectations of these studies exceed their capabilities
Conservative Treatment of Low-Energy Wounds
Most low-velocity gunshot wounds may be safely treated nonopera-tively, with simple local wound care (superficial irrigation and careful cleaning followed by a dressing, with or without antibi-otics) and outpatient management (Fig 5).2,19,33,34,41,42 These Òminor woundsÓ include low-energy un-contaminated injuries of skin, sub-cutaneous tissue, and muscle and fractures not requiring operative stabilization Tetanus prophylaxis with a reinforcing booster of 0.5
mL of tetanus toxoid is indicated for all gunshot-wound patients who are not completely immu-nized (fewer than three immuniza-tions) or who have uncertain im-munization histories.37,43 Anyone who has not had an immunization within 5 years requires a booster Those not previously immunized will also require a minimum of 250
to 500 units of human tetanus im-mune globulin.13,37,43
Aside from perioperative prophy-laxis, antibiotics are probably re-quired only for grossly contaminated wounds (Table 2).19,21,33,34,37,41,42,44-48 Dickey et al33reported similar rates
of infection in a prospective random-ized study of 73 patients treated with
or without antibiotics However, because contamination is not always apparent, most authors still recom-mend routine prophylaxis.19,34,41,44,45 Hansraj et al45 have suggested treatment for 2 days with an intra-venous antibiotic, such as cefazolin, for minor wounds with cortical bone defects In their study, substitution
of a long-acting, broad-spectrum cephalosporin (ceftriaxone) allowed discharge 1 day earlier than for patients treated with cefazolin, and
Trang 9Signs of vascular injury?
No
Duplex Doppler
Negative
Observe
Exploration*
Positive
Negative Positive
Negative Positive
Exploration*
Angiography
Yes
Yes
Signs of vascular injury?
Yes No
If proximate injury, † intraoperative angiography
Low-energy wound
Discharge home (if no other injuries)
High-energy wound
Exploration or intraoperative angiography
Extremity gunshot injury with high-energy wound, severe contamination, joint penetration, unstable fracture requiring surgical stabilization, or clinically unstable patient with signs and symptoms of vascular injury?
ABCs of trauma care Tetanus prophylaxis Initial local debridement in ED Cleanse with povidone and normal saline Sterile dressing
Consider initial dose of cefazolin, 1 g Splint unstable fracture
Definitive wound and fracture care:
Local debridement in ED Irrigation of wound Splint or cast, as fracture dictates Ciprofloxacin, 750 mg PO bid x 3 days (alternative: cephalexin or dicloxacillin) Closure by secondary intention
Definitive wound and fracture care:
Irrigation and local debridement in OR Arthroscopy or arthrotomy for joint penetration Stabilize as fracture pattern dictates Cefazolin, 1 g IV q8h x 48-72 h Closure by secondary intention
Definitive wound and fracture care:
Irrigation and local debridement in OR
Stabilize as fracture pattern dictates
Cefazolin, 1 g IV q8h x 48-72 h
Closure by secondary intention
Definitive wound and fracture care:
Irrigation and local debridement in OR Stabilize as fracture pattern dictates Cefazolin, 1 g IV q8h x 48-72 h Closure by secondary intention
Aggressive irrigation and debridement in OR Excise contaminated tissue
Explore wound tract External fixation common (possibly IM nail, rarely ORIF)
IV antibiotics as per open-fracture protocols (type I, II, or III), continue at least 48-72 h, but also until wounds are clean (up to 1-2 weeks for severe contamination) Repeat surgical debridement q48h until wounds are clean
Closure by secondary intention (possible skin graft or flap)
Figure 5 Suggested treatment for gunshot wounds Abbreviations: bid = twice a day; ED = emergency department; IM = intramuscular;
IV = intravenous; OR = operating room; ORIF = open reduction and internal fixation; PO = by mouth; q8h = every 8 hours, * = guidelines for exploration: exploration is appropriate unless the injury involves only a single vessel below the trifurcation of the popliteal artery or distal to the midforearm (such an injury is not generally explored unless there is a diagnosis of compartment syndrome, arteriovenous fis-tula, or pseudoaneurysm); † = proximate injuries are defined as those in which the missile track passes within 1 inch of a known anatomic path of a major vessel; ‡ = if there are ÒsoftÓ signs of vascular injury, can consider duplex Doppler first.
Trang 10Table 2
Suggested Treatment Regimens for Gunshot Wounds *
Hansraj et al45 Prospective Low-velocity with minor fractures Ceftriaxone, 1g IV qd ×2 doses, or
(excludes head, spine, feet) cefazolin, 1g IV q8h ×7 doses
Ordog et al37 Retrospective Minor (87% low-velocity, 4%-6% Usually cephalosporin or
with fractures) dicloxacillin PO
Geissler et al41 Prospective Low-velocity with minor fractures Cefonicid, 1g IM ×1, or
cefazolin, 1g q8h ×48 h
Dickey et al33 Prospective Low-velocity with minor fractures Cefazolin, 1g IV q8h ×24 h
randomized
Woloszyn et al19 Retrospective Low-velocity fractures (13% IV antibiotics ×3d or cephalexin,
required open reduction and 250-500 mg PO qid ×7-10 d internal fixation or arthrotomy)
Brettler et al48 Retrospective Low-velocity (53% with fractures, Cephalothin, 2 g IV initially,
15% requiring emergent surgery) then ×3 d (92% of patients),
or other antibiotics (8%)
Patzakis et al34 Prospective All gunshot fractures Penicillin/streptomycin or
weight in divided doses q6h
IV ×10-14 d
Brien et al44 Retrospective Low-velocity fractures First-generation cephalosporin plus
aminoglycoside, IV ×72 h
Molinari et al46 Retrospective Low-velocity fractures Varying short courses of IV
antibiotics
Nowotarski et al47 Retrospective Low- to medium-velocity fractures Cefazolin, IV ×48 h (average)
Wright et al21 Retrospective Low-velocity fractures First-generation cephalosporin,
IV ×48 h Knapp et al42 Prospective Low-velocity fractures Cephapirin, 2 g q4h plus
ciprofloxacin, 750 mg bid ×3 d
* Abbreviations: bid = twice a day; ED = emergency department; IM = intramuscular; IV = intravenous; NS = normal saline;
OR = operating room; PO = by mouth; q8h = every 8 hours; qd = every day; qid = four times a day.
ÒMinorÓ fractures defined as stable fractures that did not require surgical stabilization (i.e., patients underwent closed fracture treatment).
à Same wound care as would have been performed in ED for wounds with nonoperative fractures.
¤ Some patients counted more than once due to multiple fractures.
¦ Historical control (randomized retrospective).
# No statistical significance between results for two treatments.