3.1 Ballistics

The muzzle velocity of the projectile determines whether it is classified as low or high. High velocity is defined as being greater than 600 ​m per second. Civilian injuries were once almost exclusively inflicted by low velocity handguns however a greater proportion of injuries from high powered weapons are now more commonplace in the civilian setting.^3,4

3.2 Projectile pathology

Projectiles and tissues interact in permanent and temporary cavities.⁵ The permanent cavity occurs from the direct trauma on the tissue from the projectile. This is the main mode of injury arising from low velocity bullets. The temporary cavity results from lateral tissue expansion secondary to high velocity injuries.⁵ Skin, blood vessels, muscle and other elastic tissue will recoil when a projectile traverses through them, however modern day bullets, will often fragment on impact when striking bone (which is inelastic).⁵ The volume of bullet fragments adjacent to the fracture site will inversely correlate with healing rates which is unrelated to the severity of comminution.⁶

3.3 Epidemiology

The rising prevalence of gunshot injuries throughout urban and rural communities’ worldwide continue to put a strain on health services.⁷ Extremity injuries account for 19.7% of all GSW injuries.⁸ The incidence in the United States of GSWs is 3.88 per 100,000 people^9,10 with their 90-day cost per patient for tibia/fibula gunshot fractures being $342,316.92.¹⁰ Unfortunately, many countries lack a national database which is a critical component required to design injury prevention programmes.⁹

The largest epidemiological GSW study in Sweden, (n ​= ​235) between 2005 and 2016, at a major urban trauma centre, found an increasing incidence of civilian gunshot injuries over the study period, with an associated lack of contemporary studies published in that time.¹¹ The lower extremity was the commonest anatomical location of injury (38%), and upper extremity was 15%. Fracture surgery (42%) was the commonest surgical intervention required, followed by laparotomy.¹¹

3.4 Intentional versus unintentional injury

Intentional injuries have been found to be associated with longer hospital admission and higher mortality rates when compared to unintentional injuries when using bivariate analysis.¹² Various injury combinations inclusive of bone, vascular, musculotendinous and nerve injuries require an in depth knowledge of their relationships to adequately evaluate and treat these injuries.⁷

3.5 Initial evaluation of the gunshot victim

The Red Cross Wound classification (RCWC) may be used to predict the treatment requirements in paediatric¹³ and adult¹⁴ gunshot victims. The grading system (grades 1 to 3), is based on the combined sizes of the entry and exit wounds, presence of a cavity, presence of fracture (and whether it's simple or comminuted), presence of associated vital structure injury (e.g. nerve, artery) and bullet fragments on X-Ray. Grade 1: skin defect <10 ​cm, absent cavity with simple or no fracture, Grade 2: skin defect <10 ​cm, cavity present with significant comminution, Grade 3: skin defect >10 ​cm, cavity present with significant comminution.¹³ The RCWC guides early treatment by evaluating the need for a combination of: wound debridement, saline irrigation, and plaster versus surgical fixation. Grade 3 injures are associated with prolonged admission time, greater need for blood transfusion and multiple surgeries per patient.¹⁴

3.6 Associated neurological injury/vascular injury

Nerves run in close proximity to bones and vascular structures hence nerve and vascular injuries not uncommonly, occur concomitantly.⁷ Humeral gunshot fractures may have up to a 58% association with a major nerve injury and a 15% association with a major vascular injury.¹⁵ Patients requiring vascular repair ought to have the fracture fixed prior to the vascular repair, to reduce the risk of subsequent disruption of the repair.¹⁶ A large study documented a 43.1% rate of neurovascular injury in upper limb gunshot fractures¹⁷ while Burg et al. found that the commonest injured nerve in the lower limb was the deep peroneal nerve (38%).⁷ Fasciotomy may be a necessary adjunct for repair. Vascular injuries not amenable to repair are all Grade 3 injuries and require amputation to treat gangrene.¹⁴

Pannell et al.¹⁸ advocated for early exploration for nerve injury in upper limb gunshot injuries on the basis of a higher than expected rate of nerve laceration (17%) and the presence of a nerve palsy strongly correlated with nerve laceration. They also found that 80% with a vascular injury had a nerve palsy and 28% with a nerve palsy had a vascular injury.

A retrospective study consisting of 1851 GSW patients, had 48% involvement of at least one extremity, with 4% of the cases having neurological injuries.¹⁹ The authors reported a 14% incidence of gunshot extremity fractures resulting in neurologic injuries versus a 4% incidence of neurologic injury without fractures, which was statistically significant.¹⁹

Kumar et al.²⁰ demonstrated good results when treating high energy radial nerve neuropraxias expectantly and performed nerve repair at 4 weeks, in cases where there was structural discontinuity in the radial nerve. Wounds with obvious nerve injuries have treatment involving epineural repair, or nerve tagging and delayed nerve grafting if the nerve ends are damaged, or the wound is significantly contaminated.⁷ Of note, gunshot fractures with associated injuries and comminution, reflect the energy imparted to the limb and may have infection rates as high as 22%.²¹

3.7 Antibiotic protocols

A survey involving 173 Orthopaedic Trauma Association members published in 2018, showed that there was consensus in 54% on the topic of joint exploration in conjunction with perioperative antibiotics to treat traumatic arthrotomies from gunshot injuries. Irrigation, tract debridement, perioperative antibiotics and fixation was the treatment of choice for tibial gunshot fractures in 55%. Only 30% of respondents could attest to having an established protocol for treating gunshot fractures at their institutions.²²

Antibiotic regimes for gunshot fractures have varied from 1 to 3 days of coverage, many times based on surgeon's preference. The basis for the duration of antibiotic coverage specifically for nonoperative cases, or those treated surgically, requires further study in the literature.²¹ Historically, when the vast majority of gunshot fractures were exclusively due to low velocity weapons, it was felt that those injuries in civilian practice may be managed akin to a closed fracture and so the absolute need for antibiotics was debated.²³

A particular literature review found no significant benefit using antibiotics for low-velocity gunshot fractures treated nonoperatively; but, the statistical power in their review was low.²⁴ Other studies demonstrated that antibiotics reduce deep infection risk including osteomyelitis in low-energy GSW patients using a first-generation cephalosporin22,25.

Kumar et al.²⁰ utilised an antibiotic protocol of cefoperazone, sulbactum, amikacin, and metronidazole for 3 days postoperatively, to achieve broad spectrum coverage and sited 2 cases of deep infection and nil cases of chronic infections. Contrastingly, an academic emergency department treating gunshot fracture victims requiring operative care, concluded that expanded antibiotic groups were not superior to monotherapy in reducing post-traumatic infections.²⁶ Monotherapy with cefazolin or clindamycin was statistically just as effective as treatment with an expanded gram-negative group consisting of either an extended-spectrum beta-lactam, or an aminoglycoside, or just as effective as expanded treatment with a fluoroquinolone.²⁶ Regardless of wound characteristics, 24–72 ​h of prophylactic antibiotics is still the current practice.¹

3.8 Non-operative management

Stable gunshot fractures often do not require fixation.⁷ Despite reports of upper limb gunshot fractures not requiring fixation, coming out of centres with limited access to the operating theatre or implants, those reports also had infection rates approximating 11.8%.¹⁷ Low energy humeral gunshot fractures however, usually have relatively little soft tissue and bone disruption, and are often successfully treated with Sarmiento bracing.¹⁵

3.9 Fixation

There are various factors which guide the decision on the need and timing for primary fixation to stabilise gunshot fractures. These include: the fracture characteristics, wound characteristics, associated neurovascular injuries, the nature of any other associated injuries (Orthopaedic or otherwise), and the general condition of the patient.⁷ Low velocity gunshot fractures tend to fall into Gustilo and Anderson grades I or II, and definitive stabilization ranges from splints, casts, external fixation to internal fixation.¹⁷ Multiple studies employ external fixation as the commonest stabilization modality both definitively or temporarily,⁷ however a series with 133 patients with low-velocity gunshot fractures had immediate intramedullary (IM) fixation in 46%, delayed IM nailing post initial external fixation in approximately 6%, and the majority of the remaining cases were plated. Their overall infection rate was 5.8%.²⁷

It was felt that significant fracture comminution, associated vascular injury and major soft tissue injury, each on their own merit necessitated initial external fixation, followed by staged fracture management, in order to achieve optimal results.¹⁵ However, high energy humeral gunshot fractures have been successfully treated emergently with plate osteosynthesis, despite those authors willingness to perform external fixation if deemed necessary, and all healed with no long term infections.²⁰

3.10 Formal irrigation

For low energy gunshot injuries, various authors advocated for wounds superficial to the fascia to be irrigated and debrided in the emergency room without antibiotic treatment. Injuries with deep muscle or bony involvement were managed with operative irrigation and debridement and IV antibiotics for 1–2 days depending on the injury extent.²⁷

3.11 Soft tissue debridement/bullet removal

For low-velocity ballistic fractures requiring fixation, superficial debridement provides favourable results when compared to formal irrigation and deep debridement, except in the following associated scenarios: large soft tissue defects, significant wound contamination, vascular injury and compartment syndrome.²⁵ Debridement is recommended for wounds located in the hand, distal tibia, or foot due to increased infection risk. Regardless of the location, dressings are changed every 3–5 days.¹

A 2021 study of tibial shaft gunshot fractures (121 patients), used a protocol which included deep debridement which they defined as removal of bone fragments. They found a positive correlation between deep debridement and deep infection, and had an overall complication rate of 49%.²⁸ The unanswered question is whether or not the injury location, injury severity, or performance of the deep debridement in 45% of the cases led to the overall high infection rate.²⁸

A 2022 survey of 427 trauma surgeons, found that only 14.5% of them worked in an institution which had a standard protocol for bullet removal, despite the fact that 88% of them worked in an academic level 1 trauma centre. Pain (88%) and a palpable bullet were the most frequent bullet removal indications, with half performing removal at a subsequent hospitalization.²⁹ Most of the existing literature on retained bullets is low powered data, hence better quality data is required to analyse this issue which is rising in incidence.¹

3.12 Traumatic arthrotomy

A 2019 study investigated the risk for developing septic arthritis following a traumatic arthrotomy secondary to GSW, in two treatment groups: the operative group who was managed with irrigation and debridement, and nonoperative group which was treated with wound care plus antibiotics. The groups were compared using a 2-tailed t-test. The commonest joints involved were the knee (73.9%), elbow and shoulder at 8.7% each. The nonoperative group had a 12.5% superficial wound infection rate compared to 2.6% in the operative group, which was not statistically significant. No patient developed septic arthritis and all infections resolved with oral antibiotics.³⁰

3.13 Management of high velocity extremity gunshot fractures

Yeganeh et al., in 2022³¹ prospectively studied gunshot fracture patients most of whom had Gustilo Grade IIIa injuries. The outcomes during the six months follow-up: 18% infections, 26% nonunions, and 10% malunions were observed. Grade IIIb injuries overall had higher infection rates and IIIc injuries had higher nonunion rates.³⁰ Extensive debridement and IV antibiotics as per standard open fracture management, because of the higher infection rates, are advocated for high-velocity gunshot fractures as these injuries tend to fall into one of the Grade III groups. Other indications for more aggressive surgical management include subfascial injuries, compartment syndrome, periarticular fractures, neurovascular injuries, necrosis or contamination of soft tissue.¹ Of note, a prospective study which included injuries from AK-47's, had an overall wound infection rate of 46%.

A 2021 study formulated a protocol for tibial shaft gunshot fractures in which all patients received debridement if the wound was accessible and had evidence foreign bodies or significant soft tissue or bony injury. Deep debridement when performed, involved bone fragment removal.²⁸ An initial external fixator was placed when there was concern by the treating surgeons of the soft tissue status with a view for subsequent IM nailing or plating, once the soft tissue improved. Their non-union rate was 20% and 26% of study required revision.²⁸ Of note, for high velocity humerus gunshot fractures, Kumar et al. achieved 100% union and no sequelae of chronic infection using primary plate osteosynthesis along with debridement within 6 ​h, staged nerve pair and immediate vascular repair.²⁰