Fig. 1 A clinical photograph (taken at presentation) of a forearm injured with a high-energy rifle
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AAOS Now

Published 11/1/2019
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Jason Lowe, MD; Megan Couso, MD; Aditya Manoharan, MD; James Ficke, MD, FAAOS

Ballistic Trauma Basics for Orthopaedic Surgeons

A firearm injury is defined as “a gunshot wound (GSW) or penetrating injury resulting from a weapon using a powder charge to fire a projectile.” The resultant injury often involves the musculoskeletal system and requires orthopaedic treatment.

Like blunt force trauma, ballistic trauma is seen in rural and urban settings alike, and injury severity presents on a spectrum from minor to mortal. Ballistic kinetics must be considered in the assessment and treatment of GSWs, as well as the projectile’s course through the body, in addition to the presence and location of residual wadding or bullet fragments. This article reviews firearm ballistics, GSW evaluation and treatment, and demographics of non­fatal GSWs in the United States.

Ballistics

Ballistics is the study of mechanics, flight behavior, and impact of projectiles. The extent of mechanical damage a projectile imparts is primarily dependent on kinetic energy (KE = 1/2MV2), where (M) is mass or caliber of the projectile and (V) is velocity.

Tissue injury occurs via both direct and indirect mechanisms following firearm injury. Direct damage is caused by the permanent wound cavity produced by the projectile’s physical size and shape as it first enters the body and then as it deforms. Indirect injury arises from a temporary cavity produced as tissue accelerates away from the bullet’s path, which occurs as KE is transferred from the projectile to adjacent tissues. This cavity exists for milliseconds then collapses toward the geometric bullet path. Still, its force is sufficient to cause indirect fractures (typically wedge shaped) as bones bend away from the projectile. Clothing has been shown to increase the size and depth of the temporary cavity and is linked to more severe fractures.

Velocity has a greater contribution to KE, and firearms are classified as either high-velocity (> 2,000 feet per second) or low-velocity (< 2,000 feet per second) based on the speed at which a bullet leaves the gun barrel. It is important in the clinical setting to determine whether an injury was created by a high- or low-velocity ballistic, as velocity changes treatment paradigms. Handguns inflict low- to medium-energy injuries. Essentially, all rifle fire (sporting and military weapons) is considered high-energy (Figs. 1 and 2). Shotguns are considered high-energy when wounds are inflicted within 10 feet and can cause devastating injuries (Fig. 3). In addition, shotgun injuries are unique because each cartridge has wadding that can embed within soft tissues and become an infection nidus. Suspicion of retained wadding should be high for all close-range shotgun injuries.

Evaluation and treatment

Evaluation of musculoskeletal firearm injuries includes a standard neurovascular exam and radiographs of the joints above and below the affected area. Intra-articular extension can occur following meta-diaphyseal gunshot fractures. CT scans of adjacent joints are often ordered and can identify fractures undetected on standard radiography. However, CT imaging is shown to change treatment plans in about 10 percent of cases.

Treatment of firearm injuries varies with the amount of energy imparted. High-energy projectiles cause greater temporary cavities and soft-tissue injuries, and they are linked to a higher risk of infection (41.0 percent) versus low-energy firearm injuries (9.5 percent). For this reason, initial management focuses on timely antibiotics and early and serial débridement, coupled with provisional fixation placed outside the zone of injury. Definitive fracture management is delayed until the soft-tissue envelope is stable. In contrast, there is no consensus on the management of low-velocity gunshot fractures (LVGSFs). Some studies have suggested that LVGSFs be managed like closed fractures because of similar infection and reoperation rates.

Antibiotics

Firearm injuries are not sterile wounds. For high-energy ballistic fractures, the Surgical Infection Society and the Prevention of Combat-related Infections Guidelines Panel recommend prompt administration of first-generation cephalosporin and continued antibiotics for one to three days post-injury for infection prophylaxis. The guideline panel specifically recommends against the prophylactic use of aminoglycosides or penicillin.

The utility of antibiotics following LVGSFs remains in question. A survey of the Orthopaedic Trauma Association membership showed that 86 percent of trauma surgeons provide routine antibiotics, with Ancef being most common. Studies have suggested that antibiotics reduce infection rates in purely soft-
tissue trauma, but this is unproven for fractures.

Surgical débridement

Serial débridement of high-energy injuries is required, with strong recommendations for delayed wound closure after the soft tissues stabilize, typically three to five days after injury. Determining when to débride an LVGSF is less straightforward. Low-energy injuries should be débrided if (1) there are retained intra-articular bullet fragments, (2) the wound is part of the dissection field for fixation, or (3) there is evidence of significant soft-tissue damage. Retained intra-articular projectiles should be removed to prevent synovitis, mechanical joint destruction, elevated serum lead levels, and potential long-term lead toxicity. Routine débridement of entry and exit wounds should be avoided because of the low incidence of infection (2 percent). Routine surgical débridement is not recommended for arthrotomies without retained fragments or fractures that do not require fixation. However, LVGSFs involving a joint are associated with 15 percent chondral and 42 percent meniscal injuries and may require later arthroscopic treatment.

Fig. 1 A clinical photograph (taken at presentation) of a forearm injured with a high-energy rifle
COURTESY OF JASON LOWE, MD
Fig. 2 A clinical photograph of the high-energy rifle injury from Fig. 1 after two débridements
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Fig. 3 A clinical photograph of a shoulder after a close-range shotgun blast
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Table 1 Nonfatal gunshot wounds in the United States 2007–2015
Centers for Disease Control and Prevention: Nonfatal Injury Reports, 2000–2017. Available at: https://webappa.cdc.gov/sasweb/ncipc/nfirates.html. Accessed October 22, 2019.
A 53-year-old hunter fell asleep with his rifle, a 270 Winchester. The rifle fell and discharged. He presented with the pictured wounds. He was taken to the operating room (OR) with vascular surgery for revascularization. Ischemia time was six hours. Orthopaedics came in to perform débridement and place antibiotic spacer and fasciotomies of the forearm. His bicep was completely necrotic and débrided. Half of the tricep was nonviable, and 8 cm of median and radial nerve was missing. Approximately 16 cm of humerus was missing. He returned to the OR 48 hours later for guillotine amputation. He returned in another 48 hours for repeat débridement and closure of the wound using atypical flaps to preserve length.
COURTESY OF JASON LOWE, MD
A 53-year-old hunter fell asleep with his rifle, a 270 Winchester. The rifle fell and discharged. He presented with the pictured wounds. He was taken to the operating room (OR) with vascular surgery for revascularization. Ischemia time was six hours. Orthopaedics came in to perform débridement and place antibiotic spacer and fasciotomies of the forearm. His bicep was completely necrotic and débrided. Half of the tricep was nonviable, and 8 cm of median and radial nerve was missing. Approximately 16 cm of humerus was missing. He returned to the OR 48 hours later for guillotine amputation. He returned in another 48 hours for repeat débridement and closure of the wound using atypical flaps to preserve length.
COURTESY OF JASON LOWE, MD

Ballistic acetabular and pelvic ring injuries, when the projectile violated the bowel, are a separate entity. Though counterintuitive, routine fracture débridement has unproven effectiveness in pelvic injuries. Consultation and treatment decisions made in concert with general trauma service regarding bowel or perineal injuries are recommended. The literature suggests that infection rates are high with or without bony débridement.

Demographics

Both fatal and nonfatal firearm-related injuries are reported to national databases. According to the Centers for Disease Control and Prevention (CDC), there were 39,773 firearm-related
fatalities in 2017 compared to 11,671 in 2001. Focusing on nonfatal injuries that orthopaedic surgeons may see, the CDC reports subtle variations over time (Table 1, available in the online version at www.aaosnow.org). Other databases suggest the incidence of nonfatal GSWs from 2010 to 2012 to be 67,197 per annum, with 53.9 percent requiring hospitalization. Male sex accounted for 87 percent of such events, and the most common circumstances were assault or unintentional discharge. America’s youth, those aged 15–24 years, have the highest incidence of nonfatal GSWs, at 65.6 per 100,000 persons. The lower extremity is injured in 35 percent of assaults and 43 percent of unintentional GSWs. Southern states have the highest incidence of nonfatal and fatal GSWs. The estimated healthcare cost related to GSWs is $48 billion in lifetime medical costs and work lost.

Pediatrics

Children are not immune to firearm-related injuries. About 5,790 pediatric GSWs occur and are treated annually in the United States, representing 7.9 of 100,000 children. Approximately 1,300 are fatal. Of those, 84 percent occur in boys (n = 12.9/100,000 children), 71 percent are assault-related, and those aged 13–17 years (n = 24.4/100,000) are most commonly affected. Most unintentional pediatric shootings occur when someone else is handling the firearm. Among older children, the firearm often is thought to be empty, and in younger children,it often is thought to be a toy.

Mass shootings

In recent years, there seems to be an increase in mass shootings. Exact figures on mass shooting events vary widely among reports (seven to 371 between 2015 and 2019) because there is no single agreed-upon definition. The number of people shot, lethal or nonlethal wounds, and the shooter’s motive (indiscriminate versus domestic, gang violence, drug- or organized crime-related) are among the variables that may change the recorded definition of a mass shooting.

For orthopaedic surgeons, there are two aspects of any multivictim shooting event to consider. First, as with any ballistic trauma, the energy imparted must be assessed so the injury can be classified and treated accordingly. Second, multiple-victim shootings are triaged as any disaster as described by the National Disaster Life Support Foundation such that the best care can be rendered to the greatest number of patients.

Conclusion

Firearm injuries continue to be a significant management challenge for orthopaedic surgeons covering trauma call or occasionally in unpredictable situations such as mass shootings. In light of the frequency and variety of musculoskeletal ballistic injuries, orthopaedic trainees should receive dedicated teaching related to their management. Orthopaedic departments and surgeons should consider adopting protocols for the management of ballistic trauma.

Jason Lowe, MD, is an associate professor of orthopaedic trauma surgery at Banner University Medical Center and the University of Arizona–Tucson.

Megan Couso, MD, is a resident of orthopaedic surgery at Banner University Medical Center and the University of Arizona–Tucson.

Aditya Manoharan, MD, is a resident of orthopaedic surgery at Banner University Medical Center and the University of Arizona–Tucson.

James Ficke, MD, FAAOS, is a colonel of the United States Army (retired) and the Robert A. Robinson Professor and chair of orthopaedic surgery at Johns Hopkins School of Medicine.

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