Ballistics, Pathology, and Treatment Recommendations in GSW | ORR - Dove Medical Press

Introduction

The civilian use of firearms is a common cause of traumatic injury in the United States. It is estimated that an average of 120,232 firearm injuries occurred yearly from 2009 to 2017.1 Knowledge regarding gunshot wound (GSW) injury and management was chiefly derived from experience garnered during the major wars of the 20th century. Existing guidelines were written when high velocity firearms and deforming rounds, which create more extensive tissue damage, were predominantly restricted to the military. However, advances in weapons technology and the increased accessibility of military grade firearms to civilians has changed the nature of domestic GSW injury, thereby complicating clinical decision-making.2,3

Despite the prevalence of GSWs, especially in high volume trauma centers, treatment decisions are still largely driven by anecdotal beliefs. A common myth is that the heat produced by gun powder ignition during firearm discharge is sufficient to sterilize the bullet.4 Wolf et al disproved this notion by coating bullets with a small amount of S. aureus, firing into sterile ballistics blocks, and culturing the same S. aureus from the bullet tracts.5 A GSW creates an open path of entry in which projectiles and their components can transport bacteria and debris from the skin flora, clothing, environment, or other intermediate targets directly into a wound.4,6,7 Despite the evolution of understanding with regard to possible infection, historical misconceptions have likely played a role in the lack of lucid consensus on antibiotic use in GSWs.8–10

Additionally, the literature lacks large data pools and comprehensive guidelines regarding the management of retained bullets. According to a 2022 survey, only 14.5% of participating surgeons reported having institution policies for bullet removal.11 Many clinicians believe that bullet removal and thorough debridement is indicated in all cases. Yet, specific tissue involvement and injury presentation vary widely and dictate the method and degree of intervention. Often, bullet removal and formal debridement are unnecessary and can lead to additional tissue damage or complications such as infection, iatrogenic neurovascular injury, deep vein thrombosis, and bleeding. Contrary to common belief, risk of lead toxicity is uncommon, unless bullets have come to rest within synovial fluid or an intervertebral disk.12

Currently, there is no comprehensive review that provides adequate information covering projectile ballistics, pathology, and management. Further, there is a dearth of literature addressing recent advances in the field of projectile-related trauma, specifically injuries resulting in retained bullets. We aim to aggregate the available yet dispersed findings regarding GSW etiology and treatment, particularly for retained bullet cases. We will also discuss the importance of interventions (eg, prophylactic antibiotic use and debridement) that minimize complication risk, while also reducing care induced harm.

Materials and Methods

The authors performed a comprehensive review of the PubMed, MEDLINE, and EMBASE databases using an extensive combination of keywords outlined in Table 1. The literature search focused on clinical evidence-based data regarding GSW and retained bullet ballistics, complications, and treatment recommendations to present the current understanding of GSW and retained bullet management.

Table 1 PubMed Search Terms Used by Section

Ballistics

The characteristic path of a bullet originating from a firearm, exhibiting projectile flight, and striking an object, can be described by applying the principles internal, external, and terminal ballistics. Firearms can be categorized in many ways including shape, action, and ammunition type. While there are countless factors that can be applied and dissected to fully understand the behavior of projectiles originating from firearms, we will only present what we have found to be most pertinent to the understanding of GSW etiology and treatment.

Categorization

Firearms responsible for GSWs are commonly stratified by the velocity of the expelled projectile. High-velocity projectile injuries are typically from firearms with a muzzle velocity greater than 2000 ft/s (commonly rifle calibers) and are associated with more substantial tissue damage.13 Low-velocity projectile injuries are caused by firearms with muzzle velocities less than 2,000 ft/s (commonly pistol calibers).13 Shotguns are a common example of a low-velocity firearm (1,000–1,500 ft/s), but they provide a unique ballistics pattern that differs from the behavior of a single projectile.14–17

While categorizing firearms by projectile velocity alone is convenient, this neglects much of the nuanced outcomes of wound ballistics. For example, when a low-velocity shotgun is fired at close range, a high-velocity type wound results, due to increased energy transfer.18 Alternatively, a physician may unnecessarily excise viable tissue simply because the wound came from a high velocity round.19

Instead of evaluating wounds as high or low velocity calibers, consideration of the amount of kinetic energy (KE = 1/2 MV2) possessed by a projectile at the time of impact is much more important. The efficiency of energy transfer is dependent on multiple factors including the trajectory stability, distance traveled, entrance profile of the projectile, and the amount of yaw (the angle of deviation from the projectile's long-axis).17,18 The caliber and material of the bullet, the tissue type impacted, mechanism of tissue disruption, and trajectory within the body, also contribute to the projectile's energy transfer.17,18 Therefore, in the setting of wound ballistics, designating the implicated bullet in a GSW as "high-energy" and "low-energy" is a more useful categorization method for describing the extent and nature of multi-tissue damage than velocity alone.

Internal Ballistics

Internal ballistics describe the path a projectile takes within a gun, from the breech to the muzzle, which can be seen in Figure 1A. Internal ballistics are influenced by factors such as the type of gun powder, primer, and other characteristics of the ammunition, as well as the chamber, rifling, choke (constriction), barrel length, and other engineered properties of firearms. Technical advancements regarding internal ballistics have allowed for the increased projectile velocity, energy, and accuracy.

Figure 1 Phases of Ballistics.

Notes: (A) Internal Ballistics occur within the firearm. (B) External Ballistics describe the period that occurs after the projectile departs from the firearm and before it reaches the target. The projectile trajectory (t) can vary along its flight path direction (x) if the nose of the bullet deviates on its vertical axis, which is known as pitch (y), or the horizontal axis, known as yaw (z). (C) Terminal or Wound Ballistics describe the effect of the projectile once it has struck a target or victim.

Bullets are available in a wide variety and differ in material, size, shape, and other design aspects that affect flight behavior, yaw, KE, penetration capability, and wounding potential (Figure 2). Bullets are primarily composed of lead due to its high density, mass, and thus KE, although when shot at over 2,000 ft/s, high barrel temperature can cause them to deform.20,21 To mitigate temperature induced deformation, bullets are commonly produced with lead alloys or are encased with a copper or copper alloy jacket.20,21

Figure 2 Ammunition Anatomy.

Notes: Simplified sketches showcasing the general appearance of different kinds of ammunition, cartridges, rounds, or shells. (A) High velocity/energy cartridges, typically fired from rifles, are designed for long range use for hunting or armed conflict. (B) Low velocity/energy rounds, typically used in handguns. The sketches depict one round with a hollow point and one with a round point. (C) Shotgun ammunition, typically used in muzzle loading rifles, designed for short-range targets. (D) Ammunition generally consists of the following: (i) Bullet (projectile); (iii) Casing; (v) Propellant; (vi) Primer; (vii) Rim. Uniquely, shotgun shells contain (ii) Pellets (projectiles) and (iv) Wadding.

External Ballistics

The course taken by the bullet between exiting the firearm and contacting a target is explained using external ballistics, which can be seen in Figure 1B. The bullet type, casing, length, and caliber (diameter) are central components that influence external ballistics. Additionally, the rotation caused by the rifling of the barrel, which improves flight stability and accuracy, and external forces such as gravity and drag act on the projectile determining its flight path.

The distance between a firearm and its target, as well as its initial projectile velocity, both play a significant role in wounding potential. High-velocity weapons retain a significant amount of KE at a short distance, while low-velocity projectiles quickly lose substantial energy. However, at a close range, both high- and low-velocity projectiles may retain a high percentage of their KE.15

The drag force can be altered by the shape, size, and behavioral exhibited by a bullet throughout its projectile trajectory. An ideal, aerodynamic bullet experiences minimal yaw, tumbling or roll, and has a low drag coefficient, which leads to a flattened projectile trajectory and maximizes the amount of kinetic energy retained when contacting its target.22,23 Increased yaw and the presence of tumbling (the complete loss of gyroscopic stability) both cause the drag force on the bullet to increase and its KE to decrease.24

Terminal (Wound) Ballistics

Terminal ballistics, represented in Figure 1C, describe the effect projectiles induce on their target upon contact, which, in the case of this paper, is living tissue.15 This specific subordinate of terminal ballistics is termed wound ballistics and characterizes how diverse projectiles create wounds and how living tissues react to projectile injury, which is depicted in Figure 3.18 Bullets can be broadly classified by whether they are deforming (expanding) or non-deforming (non-expanding). Non-deforming and partially deforming bullets remain intact and typically result in greater penetration yet result in less collateral tissue damage than deforming projectile GSWs (Figure 3A and C).20,21 Due to their greater penetration, non-deforming rounds, such as full metal jackets, round noses, wadcutters, and semi-wadcutters, are more likely to create exit wounds.25 In contrast, deforming and fragmenting bullets immediately expand on impact, increasing the total contact area between bullet and tissue, which results in a larger wound cavity (Figure 3B and D). This expansion causes a braking effect, transferring all of the bullets KE to the target, maximizing tissue damage, and rarely exiting the body.20,25,26 Therefore, deforming rounds, such as hollow points, soft points, frangible bullets, and slugs cause extensive tissue damage and disruption.14,18,25,27–31 These properties led to the Hague Convention of 1899 to prohibit the use of expanding, deformable bullets in wartime. Despite this, many law enforcement agencies have adopted hollow point handgun bullets due to their "stopping power" which prevents unintentional collateral damage.14,18 Shotgun shells behave uniquely and demonstrate complex ballistic patterns, due to the fact that they are made up of varying numbers of small metal pellets which disperse when fired (Figure 3E).16,17,29,32

Figure 3 Gunshot Wound Patterns for Various Rounds.

Notes: Simplified sketches showcasing the typical internal wound patterns caused by classes of commonly used projectiles. The permanent cavity and temporary cavity of each wound are shown in red and pink, respectively. Non-deforming rounds (A and C) may be retained or exit the body. While deforming rounds (B, D and E) can exit the body, they are more likely to be retained. (A) High-energy wound from a non-deforming round. (B) High-energy wound from a deforming round. (C) Low-energy wound from a non-deforming round. (D) Low-energy wound from a deforming round. (E) Low-energy wound from a shotgun shell (deforming round).

Penetrating GSWs

The offending bullet of a GSW will either become retained within the body or exit just after entering. If the projectile exits, only a fraction of the KE is transferred to the body, decreasing the potential energy that can be converted to tissue damage. Exit wounds tend to occur when projectiles are non-deforming, excessively powerful, or fired at a short range, or if the bullet encounters tissue that is minimal in thickness or density.18,33 In general, exit wounds tend to be larger and more irregularly shaped than corresponding entrance wounds, especially if the projectile is traveling at a high velocity, experiences expansive deformation, or tumbles and travels off-axis from its lengthwise orientation.18,33 Determining exit sites may be further complicated if bullets become fragmented or ricochet off dense material, such as bone.13,15,34 Therefore, it is advised to treat the wounds as they present and avoid labeling sites, as they are often misclassified.13,15

Retained Bullet GSWs

In contrast to exiting projectiles, retained bullets transfer the total remaining KE present at impact to the tissue encountered. Retained bullets can come to rest intact, if they remain in soft tissue, or they could strike bone or a metal implant resulting in fragmentation.25,35 Despite yaw, most intact bullets typically come to rest in tissue at 0° (nose-forward) or 180° (base-forward), causing tissue destruction no larger than the bullet's caliber.36,37 If bullet yaw is equal to 90° on contact, the resultant tissue damage can be greater than three times as extensive.36 Internal bodily impact may result in simultaneous bullet disintegration and bone fragmentation, forming numerous secondary missiles causing additive damage, increasing the cavitation volume and severity of the wound.20,24,36 Fragments of less than a gram can penetrate a depth of up to 10–15 cm within soft tissue. As an additional complication, fragmentation can result in a mix of a partially retained bullet with accompanying exit wounds.13,38

All the above factors described by ballistics interact to cause variable injury patterns that cannot simply be predicted by projectile velocity. Thus, Cooper and Ryan recommend that treatment should be indicated by wound presentation, rather than the weapon implicated.39

Projectile Pathology

While the KE transferred at impact determines penetrating capacity, the wounding potential depends on the structures impacted by the projectile.18 Gunshot injuries commonly result in diffuse soft-tissue damage, volumetric muscle loss, hemorrhage, fracture, and severe pain.40 Tissue structure varies by specific gravity or density and elasticity, which contribute to wounding potential causing inconsistent energy dissipation and tissue disruption along a bullets track.14,41

As a bullet enters the skin, tissue accelerates radially and is displaced centrifugally.42 The size of the entry wound is transiently larger than the caliber of the bullet, but typically the defect reversibly contracts to a diameter smaller than the cross-sectional area of the bullet due to the highly elastic properties of skin.42 Additionally, entry wound defects can differ depending on the shape of the implicated bullet.42 The effects of penetration are further complicated by the presence of intermediary targets such as clothing, glass, or wood, which can alter the shape, fragmentation, or trajectory of the projectile.43,44

Internally, bullets cause crushing or laceration injury leaving "permanent" tissue cavitation along their course.19,24,45 The magnitude of this permanent cavity is determined by the bullet caliber and its deformation or fragmentation within the body.24,46 A small and intact bullet traveling at a lower velocity will create a permanent cavity similar to its caliber or entry orientation.37,47 Additionally, a "temporary" cavity is created surrounding the primary cavity as the bullet stretches and strains tissues past their elastic limit.18,19,24,45,48 This continued, radial acceleration and the extent of damage are primarily determined by the bullet's velocity and the tensile properties of implicated tissues.24,46 High-energy projectiles are associated with temporary cavities reaching up to 10–30 times the size of the permanent cavity, while lower-energy projectiles create temporary cavities that are relatively the same size as the permanent cavity.24,46 Additionally, the amount of yaw demonstrates a positive relationship to temporary cavity size.24,46 In all, GSWs from high-energy projectiles tend to result in greater and more diffuse damage, whereas low-energy projectile damage is typically restricted to the path of bullets and secondary missile fragments.24,46

Fractures

Bone is anisotropic and viscoelastic, meaning it shares the properties of both a solid and liquid to some extent. While soft tissues respond to impact by "crushing and stretching" bone reacts to similar trauma by fracturing.49 Bone can fracture to varying degrees depending on impact energy and location.17,39,47,50,51 As expected, the greater the energy a bullet delivers, the more complex fracturing pattern and comminution will occur at boney entry and exit sites.47 At a velocity of just 195–200 ft/s a bullet can fracture cortical bone.7,22 Additionally, projectile contact with bone can result in secondary missiles that are propelled along the periphery of the temporary cavity, causing more extensive injury.17 Bullets can also damage the connective tissue surrounding and attaching to bone at joints.

Soft Tissue Injuries

Firearm wounds in the extremities most frequently afflict the musculoskeletal tissues but can result in more complex injuries due to the proximity with neurovascular structures, often cohabitating in a confined space.52 The temporary wound cavity from high-energy missiles can rupture capillaries and other small blood vessels, while larger arteries and nerve trunks seem to be injury resistant.17,18 Skeletal muscle appears to be especially susceptible to permanent cavitation causing cytoplasmic clotting, interstitial extravasation of blood, striation damage, and swelling of muscle fibers up to five times their normal size.17 Together, these effects can cause localized edematous response, contributing to compartment syndrome and further damaging adjacent soft tissue.53

Initial Evaluation

When GSW injury victims are assessed, details regarding the proximity and position of the shooter, number of shots fired, and the type of firearm should be collected, if possible. All bullets and fragments should be accounted for and used to determine the necessity of surgery. If the total number of entrance wounds does not equal exit wounds plus retained bullets, fragmentation, embolization, ricochet, or migration to an unsuspected location may have occurred. While the patient's history and account can be helpful for management, they may be unknown or difficult to collect, thus it is best to "treat the wound, not the weapon".54

Diagnostics

It is strongly recommended to obtain radiograph imaging of the affected extremity, as well as one body cavity above and below the wound.17 Plain film radiography taken with multiple views, can show bullet components, identify fractures, and reveal information about the bullet's internal track.7,55 Magnetic resonance imaging (MRI) is contraindicated given the metallic nature of common projectiles.56

Careful examination for the presence of other foreign materials should be completed, as it is difficult to capture clothing fragments, wadding, and certain metal jacket casings on plain film. Indicators of possible clothing infiltration can include evidence of an irregular bullet, a larger entrance wound than estimated by caliber and range, or the absence of clothing near the entrance site. CT scans offer multiple views with a higher resolution and greater sensitivity, which allows for detection of radiolucent materials, such as the fiber, paper, or plastic used in the bullet design.57 Imaging may also aid in the detection of distance injuries due to stray fragments resulting from impact, which could undergo arterial or venous embolization. Vascular injuries can be identified using digital subtraction angiography or CT angiography.58 Multiple detector CT angiography constructs a three-dimensional image that can better detect and localize vascular and soft tissue injuries in addition to bullet components and fracture details.7

If there is evidence of joint violation or intracapsular bullet material, plain radiographic imaging or joint aspiration results can provide valuable diagnostic information.59 In uncomplicated cases, arthroscopy can aid in diagnostics but the most sensitive test is a fluoroscopically assisted arthrogram.59,60 If the results are inconclusive, or the intended method of imaging is not feasible, a CT scan can be obtained.17 Whenever migration is suspected, ultrasound or intraoperative fluoroscopy should be performed to visualize the exact location of the projectile before an incision is made.61–64

Prophylactic Antibiotics

By disrupting the skin and other organs, GSWs allow microbes to be transported to damaged tissue from external and internal sources, such as the surrounding environment, clothing, the gastrointestinal and genitourinary systems, or the projectile itself.4,7–10 Both superficial and deep infections can occur due to penetrating GSW injury, with one Level I trauma center reporting infection rates as high as 15.7%.65 High energy GSWs appear to be more likely to develop infection, as a greater amount of tissue is devitalized and host defenses may be diminished.66 Following a GSW, aerobic and anaerobic organisms can rapidly multiple if introduced to tissue by the projectile.67 Specific GSW injury regions such as the hand, hip, foot, and distal tibia are associated with an increased infection risk.59,68–72 Perforation of vascular, gastrointestinal, or genitourinary tissues can also dramatically increase the risk of infection and sepsis.73–75 Additionally, nonviable, anaerobic musculature can provide an ideal growth medium for various bacterial species, including Clostridium spp.67

In the case of traumatic projectile injuries, prophylactic antibiotics are used to prevent localized infection and progression to osteomyelitis or sepsis.76 A systematic review by Sathiyakumar et al identified that 10 out of 11 studies providing "high-quality" data on antibiotic administration recommended prophylactic antibiotics for high-energy GSW injuries.10 For low-energy GSWs, four of eight studies in which patients were treated non-operatively and four of six studies with both operative and non-operative patients definitively recommended prophylactic antibiotic use.10 Although antibiotics are a mainstay of GSW treatment, there is a lack of consensus in the literature regarding the dosage, duration, route, and type of antibiotics used for preventing infection.9,10,77–79 In a recent questionnaire completed by Orthopaedic Trauma Association (OTA) members, responses exhibited wide variability in standard antibiotic treatment practices by administration route or usage at all.79 Interestingly, less experienced providers (≤5 years in practice) tended to be more aggressive in antibiotic treatment.79

Recommendations of antibiotic type vary depending on the wound presentation, level of gross contamination, bacterial species identified in culture, and patient demographics or comorbidities. Among those commonly cited are benzyl penicillin, oral fluroquinolone, IV cephalosporins (first or third generation), aminoglycoside, and/or gentamicin.13,45,72,76,80,81 Prompt administration of antibiotics is recommended.13,82 While short courses have demonstrated positive clinical outcomes in many studies, the recommended duration varies from 24 to 72 hours depending on the author or specifics of the case.13,15,59,76,78,81,82 It should be noted that antibiotics are never to be used as a substitute for surgical debridement in soft-tissue injury.18 Nevertheless, it is important to consider the bullet contaminated and treat the tract with similar antibiotic prophylaxis as other penetrating wounds.

Non-Operative Management

In general, low-energy GSWs are uncomplicated injuries with little to no bullet fragmentation, soft-tissue disruption, or bone comminution outside of the primary cavitation.83 Most low-energy GSW fractures can be treated nonoperatively according to standard closed fracture protocols in an outpatient setting.17 Non-operative intervention is also favored as surgery could unnecessarily increase risk of infection, disruption of local blood supply, and further damage soft tissue, with minimal added benefit. Superficial debridement is an acceptable substitute for surgical irrigation and debridement when the patient is negative for wound contamination, vascular injury, large soft-tissue defects, and compartment syndrome and does not require surgical fracture stabilization.10 Additionally, some cases of intra-articular GSW that lack evident pathology can be treated non-operatively.65,84

Potentially Contaminated Low-Energy GSWs

The lack of consistent antibiotic recommendations is more pronounced for low-energy GSW treatment with and without osseous involvement9,10 Many of the studies conducted assessing superficial and deep infection rates did not demonstrate statistical significance, possibly due to less devitalized tissue in low-energy wounds.39,66,68 Additionally, some concluded that appropriate debridement and immobilization of minor, low-energy GSW can negate the need for antibiotics.85 However, in an OTA questionnaire, 86% of members reported to routinely prescribing first generation cephalosporins for low-velocity ballistic fractures, despite only 26% reporting having set protocols for antibiotic use at their institution.77

A handful of studies have demonstrated that antibiotics reduce infection risk in low-energy GSW patients and minimize or eradicate the development of osteomyelitis and deep infections.10,65,73,86 Most of these studies used a first-generation cephalosporin, such as cefazolin.10,65,73,86 Meanwhile, various other studies have found no significant statistical difference in infection rates for patients who received antibiotics and those who did not.9,68,85 Marcus et al did note that the patients who did not receive antibiotics developed more severe infections.85 Additional studies assessed the differences in outcomes of low-energy GSW patients, with or without fractures, who received antibiotics through variable administration routes. These authors concluded that IV cephalosporin, IM cephalosporin, and oral fluroquinolone were equally effective in this setting.66,70,71 Likewise, no differences in infection morbidity between IV cefazolin or IV ceftriaxone was observed.87 Interestingly, one study found that there was no additional reduction in infection risk between patients who received one or multiple doses of IV cephalosporin (first generation), following low-energy GSWs with osseous involvement.73 These mixed findings further complicate the creation of specific guidelines.

In non-complicated cases such as many low-energy GSWs, entrance wound excision and bullet track irrigation are sufficient.10,45,54,68,88 A length of saline-soaked gauze can be passed through the wound to identify the bullet track, which should then receive irrigation.89 Following superficial debridement, it is advised to avoid immediate primary closure of the bullet wound as this could lead to contamination. The wound should be left open and covered with sterile dressing for delayed primary closure or healing by secondary intention.38,90

A study by Shultz et al, which retrospectively assessed the outcomes of 46 patients with low-energy GSWs, found that there was no statistically significant difference in infection risk for patients that received antibiotics, primarily cefazolin, and non-operative wound care versus those who received antibiotics and formal irrigation and debridement (I&D).91 However, it was noted that if I&D is conducted in patients with minimal soft tissue damage and minor wound contamination, it may lead to additional tissue damage and exacerbate joint stiffness.91 Additionally, a prospective, randomized clinical trial by Brunner and Fallon, comparing I&D to bedside wound care for low-energy GSWs, found similarly low rates of superficial infection in both groups.92 Thus, for traumatic low-energy GSW, conservative treatment such as bedside I&D are recommended. Additionally, most agree that routine prophylaxis is recommended in all low-energy GSWs, as contamination is not always obvious.70,81,87,93,94 Omid et al recommended that the degree of soft-tissue injury should be the main determining factor when deciding on duration, type of antibiotics, and need for debridement.13

Surgical Intervention

Recent research has better established indications for surgical intervention in management of both high and low energy GSWs, including presence of considerable tissue damage, major vascular injury, progressive neurologic deficits, obvious contamination, joint involvement, compartment syndrome, unstable fractures, tendon injuries, superficial fragments in the palm, and patients presenting at least 8 hours after injury.95,96 Of note, complex extremity GSWs with involvement of more than one organ system should be treated by a team lead by an orthopedic surgeon.97

Formal Irrigation & Debridement

The efficacy of surgical debridement in preventing infection has limited published data available and has historically been debated.74 Watters et al showed debridement did not make a significant difference unless there was concomitant gastrointestinal injury from the bullet tract.74 Shultz et al showed no statistical difference in knee infections when GSWs were treated operatively with irrigation and debridement versus nonoperatively with antibiotics and wound care.91 A debridement procedure along the bullet track may be beneficial to excise necrotic tissue and stimulate growth factor activity,98 but the specific utility after a GSW remains unclear in the literature.

In general, formal surgical debridement is recommended in cases of extensive soft-tissue damage, fascial tissue violation, necrosis, contamination, compartment syndrome, periarticular fractures with joint involvement, GI tract involvement, vascular or spinal cord injury, or advancing neurologic deficits.10,17,83,97,99 Additionally, surgical debridement is often required if the wound is in a location with increased infection risk, such as the hand, pelvis, distal tibia, or foot.81 If significant tissue disruption is present, debridement of all contaminated, devitalized, and necrotic tissue should begin promptly, ideally within 6–8 hours following injury, to reduce infection risk and promote proper wound healing.17,82,100,101 Patients presenting more than 8 hours after injury may be better candidates for surgical debridement than local wound care, as the risk of more extensive ischemia, necrosis, or infection can increase over this time.17

Assessing tissue viability can be exceedingly difficult in extensively contused or lacerated tissue in the early post-injury period, with the most important factor is determining damage being the experience of the surgeon.17,39,50,100,102 To determine if muscle tissue requires excision, the "four C's", which are color, consistency, contractility, and capacity to bleed, can be applied.23 If muscle tissue is dark, noncontractile, and non-bleeding, this can be seen as indicative of necrosis and prompt excision.82 However, if muscle viability is unclear, it can be preserved and reevaluated later to avoid excessive debridement and avoidable damage to associated vasculature.17,100 In such cases, Riddez et al recommends an early second exploration within 24 hours, if needed.82

To excise any residual marginal tissue, subsequent I&D can be implemented regularly 2–10 days following injury, depending on the state of the patient and their wounds. Following proper debridement, wounds should be left open for delayed primary closure. Sterile wound dressings should be applied and replaced every 3–5 days if there is no indication of infection. During excision and exploration, it is also crucial to excise excess debris because any foreign material, such as clothing or shotgun wadding retained within the body is subject to abscess formation and chronic wound drainage.103 If debris excision is incomplete, contrast imaging can assist in locating foreign bodies before further exploration.38

Negative pressure wound therapy, a standard treatment method for soft-tissue defects and deep wounds, should be used as it can reduce dead space and infection.83,104,105 Wound closure should be conducted in the first 10 days, as the skin edges are more mobile, making approximation less difficult.103 If wounds remain uncontaminated, early closure can be implemented with the benefits of reduced scar contracture, joint stiffness, infection risk, and length of stay in the hospital.89,103

Contaminated Complex GSWs

While there are minimal data concerning debridement practices for high-energy ballistic injuries, the existing literature promotes formal irrigation and debridement, immobilization, and delayed primary wound closure.10 High-energy GSWs require more extensive or serial irrigation and debridement due to characteristic bone combination, bullet fragmentation, and significant tissue disruption, cavitation, and necrosis.38,90,106,107

In addition to formal debridement, soft-tissue reconstruction may be necessary. High-energy injuries typically have margins ranging 1–5 mm across, although if significant tissue devitalization is present or extensive debridement is conducted, the wound size may increase requiring coverage or grafting.51 If tension is needed for wound closure, skin grafting is the most desirable option, but if neurovascular repair, osseous reconstruction, or amputation are necessitated, local rotation flaps or free tissue transfer are advised.14,22,108,109

Despite relatively few high-quality studies regarding the administration of antibiotics for high-energy and intraarticular GSWs, they remain a mainstay in treatment due to the high infection rates associated. Meade et al recommended that patients requiring surgical intervention should receive antibiotics pre-, peri-, and postoperative.52 In line with these findings, 48–72 hours of IV antibiotic administration is recommended for high-energy injury.15

If obvious contamination by foreign materials (eg, clothing), fractures requiring operative stabilization, and GSWs with intraarticular involvement are present in a low-energy injury, formal surgery may be indicated.91 Additionally, if there is any uncertainty of the involvement or extent of soft tissue damage or vascular injury is present, surgical exploration is advised, as the risk of infection is increased.67,110 If a low-energy GSW presents with an intraarticular fracture, a fracture requiring stabilization, or obvious contamination, IV cephalosporin with the possible addition of an aminoglycoside are indicated before and following surgical intervention.59,78,81

Further, Kobbe et al recommended that any highly contaminated wound or any intra-articular GSW should be given antibiotics irrespective of energy transfer.110 Cases presenting with gross wound contamination, major tissue devitalization, sizable wounds, treatment delays, or the presence of multiple injuries, are also indications for antibiotic administration.77

Treatment of Concomitant Injuries

High-energy fractures are often analogous to open fractures due to the significant soft tissue damage17,93,108 Unstable fracture patterns that require internal fixation necessitate surgical intervention for stabilization.17,81,111–113 Consulting a GSW injury guide such as the one created by Kobbe et al, which organizes low-energy (type I or II) and high-energy (type III) fractures using Gustilo-Anderson classification system, can be used to guide treatment decisions.110,114

In a retrospective study assessing treatment of femur fractures from projectiles primarily treated with an intramedullary nail, 50% of the patients with high-energy wounds developed deep infections and required serial debridement.115 Due to the elevated incidence of contamination with high-energy wounds, primary stabilization with an external fixator is advised to allow continued access for wound care.110 Stabilization can be converted to definitive osteosynthesis within 14 days after soft tissue recovery.110

If there is vascular damage, repair is ideally performed after fracture stabilization. Although there is a debate over the ideal timing for exploration and repair of peripheral nerve damage following trauma, there is consensus that nerve reconstruction, in addition to mending fractures, should be considered early in treatment.109,116–118 A recent review by MacKay et al recommended that after blunt trauma or GSW, if the zone of injury is clearly established, immediate exploration and peripheral nerve repair may be warranted as to avoid long-term nervous insufficiency.119 The advantages of early exploration include improved outcomes and shorter graft length requirements, which may be attributable to avoiding dense scar tissue formation and intraneural edema. Ultimately, the decision is subject to clinical judgment and individual patient/injury characteristics. However, when the zone of injury is unclear, a wait time of 2 to 3 weeks is advised.119

Penetrating injuries that result in vascular injury above the knee and fracture to the proximal tibia are at high risk of causing compartment syndrome.120 Fascia and skin may only need limited debridement except in cases of perforation where they must cut open to provide exposure to the underlying damaged tissue. In addition, any suspicion of compartment syndrome warrants fasciotomy.

Retained Bullet Removal

Bullets from nonfatal GSWs are not always removed during index admission, resulting in retained bullets or bullet fragments.121 Clinical and radiographic photographs of GSWs with retained bullets or bullet fragments in various locations are included in Figures 4–7. While removal is not indicated in all cases, it is reported that GSW patients who do not have the projectile extracted are at increased risk of repeat visit to the emergency department within 6 months.122 Over a 1-year period, a trauma registry identified 344 patients who were admitted for a GSW, of which 298 were nonfatal. Of these cases, 75.5% had a retained bullet fragment. 10.2% had complete removal at index admission, 15.6% had partial removal, and 74.2% had no removal. The primary indication for removal was immediate intraoperative accessibility (67.2%) and the most common location for a retained fragment was in soft tissue (58.7%). 116 of 202 patients discharged with a fragment presented for follow-up, and 11.2% returned with a retained bullet-related complication at a mean time of 130.2 days with four patients requiring removal.121

Figure 4 Hollow Point Gunshot Injury to the Shoulder.

Notes: (A) There was evidence of an acute comminuted burst fracture of the humerus including the head, neck, and proximal metadiaphysis with extensive pectoralis muscle damage, a partial laceration to the cephalic vein, and a large missing bone void of the humeral head. On radiograph, multiple free-floating metallic bullet fragments were found with the largest metallic bullet fragment measuring 1.5 cm (B and C). The wound was irrigated, and all free-floating bone fragments and necrotic or loose tissue were removed. (D) The humeral shaft fragments, articular fragments, and proximal humerus fracture were reduced. An extended Synthes small fragment plate was placed spanning both the humeral neck and shaft fractures and bone graft was applied into the bone void of the neck.

Figure 5 Gunshot Injury to the Hand from a 9 mm Pistol.

Notes: (A) Initial clinical photograph reveals a 9×5 cm wound from the gunshot injury. (B) The patient sustained a comminuted fracture of the second metacarpal with segmental bone loss and two accompanying bullet fragments. The fracture site was treated with an intramedullary headless nail and a combination of crushed bone allograft, demineralized bone matrix (DMX) puddy, and bone venous blood. (C) Radiographs eight months after the injury show persistent retained fragments.

Figure 6 Multiple Gunshot Injuries to the Torso and Thigh.

Notes: (A) The gunshot injury to the abdomen was retained anterior to L3 vertebra with accompanying comminuted fractures of the L3 and left lateral L4 vertebrae. One bullet notably struck the femoral shaft, resulting in comminuted fracture of the midshaft with multiple bullets fragments. Entry and exit wounds on radiographs are indicated with paperclips (B and C). (D) The femoral fracture was fixated with an intramedullary nail.

Figure 7 Gunshot Injury to the Lower Extremity from a High-powered Assault Rifle.

Notes: Clinical photographs show a traumatic wound measuring 16×16 cm with significant muscular, fascial, nervous and vascular injury (A and B). Comminuted and markedly displaced fractures through the mid diaphysis of the tibia and fibula with extensive shrapnel are evident on initial radiographs (C and D). A total of 16 operations were performed for this injury. During the initial operation, small pieces of fabric, bone, and metallic objects were removed, the tibial nerve was repaired, ligation of posterior tibial artery and vein was performed, and a tibial external fixator was placed. Five repeat I&D procedures were performed before the tibia was fixated with an intramedullary nail and a latissimus dorsi free flap was placed and then skin grafted (E and F). Later operations included repeat I&D and treatment of the tibial nonunion with bone grafting.

When considering bullet removal, prevention of arthritis, infection, plumbism, vascular emboli, and spontaneous migration are the main focus of treatment.17,69,123,124 Prophylactic removal is typically only recommended when a bullet is located intra-articular, intra-bursal, or on a weight-bearing surface such as the palm or sole of the foot after swelling resolves.38 If intra-articular fragments, either osteoarticular or metallic, are appreciated in imaging or by physical exam, surgical removal is also indicated.60,91

If a bullet cannot be felt with palpation or is positioned in soft tissue without joint involvement, it should generally be left alone.38 Since projectiles located in soft tissue are swiftly enclosed by avascular scar tissue, the risk of lead poisoning and infection is low.38 In these cases, surgical removal can cause more soft-tissue trauma than the GSW itself.110,125 Therefore, low energy retained bullets will not routinely be removed because formal exploration and debridement are generally not needed. Since high-energy wounds typically require debridement anyways, bullet removal will not cause significant additional damage and is therefore indicated to reduce sepsis risk. If there are high energy bullet fragments positioned away from the site of wound exploration removal will predominantly depend on the location.

Despite several techniques available to retrieve bullets and bullet fragments, there is little to no existing data to elucidate optimal treatment. A small number of studies propose that bullets with intra- and peri-articular involvement, require arthroscopic, arthrotomy, or open debridement, though this is not yet widely agreed upon.10,60 Arthroscopy possesses potential benefits over open procedures including minimal invasiveness, reduced blood-loss, decreased surgical morbidity to surrounding structures, and enhanced visualization to locate and retrieve fragments.60,126−130 A 2020 systematic review identified 31 studies with 62 patients that underwent arthroscopically assisted bullet removal.128 All 62 patients underwent successful bullet removal and only one patient was reported to have a compli...

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