33rd Annual Scientific Meeting proceedings

Gunshot injuries are uncommon but important causes of traumatic fractures in dogs and cats.^1,2 Factors to consider when addressing gunshot fractures in small animal patients include the extent of soft tissue trauma, degree of contamination, need for appropriate wound care and antibiotics, and the potential for future complications (such as delayed union, non-union, and infection). Education about the risks and benefits of treatment options should be discussed with owners to ensure they are adequately prepared for fracture management, wound care, potential complications, and the cost of treatment.

Extensive soft tissue trauma, which may not be readily apparent at the time of initial presentation, is a large variable compounding treatment/outcome of gunshot fractures. The degree of soft tissue damage after gunshot injury is related to the kinetic energy of the projectile and the degree of energy transfer from the projectile into the tissue. Projectiles that transfer the most kinetic energy, and therefor cause the most soft tissue damage, include deforming or fragmenting bullets that are fired at high velocity and close range with a low drag coefficient and limited yaw (do not deviate very much away from their long axis trajectory before contacting the target).³

Once in contact with a target, the projectile damages tissue by creating a permanent cavity and a temporary cavity. The permanent cavity is created by crush and laceration injury along the course of the projectile with a magnitude similar to that of the bullet caliber and its deformation/fragmentation. The temporary cavity surrounds the primary cavity and is due to stretch and strain of tissue as it accelerates radially and centrifugally away from the projectile. High energy projectiles can produce temporary cavities that are 10-30 times the size of the permanent cavity creating larger areas of tissue damage and increasing the potential for indirect bone fracture.^3,4

Presence of a projectile within a wound can also increase the risk of infection during fracture healing if bacteria are tracked into the wound or if devitalized tissue is left to create an environment where bacteria can flourish. Although most agree that antibiotics are an important step in treatment, there is often a lack of consensus, even in human medicine, about the type, route, dose, and duration of antibiotic treatment for gunshot fractures. Commonly used antibiotics include benzyl penicillin, oral fluoroquinolone, a 1^st or third generation cephalosporin, or an aminoglycoside.^3,5 Often, the degree of soft tissue injury is a main factor when determining antibiotic choice.

In veterinary patients, traumatic fractures caused by a projectile only made up 0.6% of all traumatic factures in a population² and current information on prognosis is sparse. Although survival after gunshot injury was noted to be 79% in one paper¹, dogs with gunshot fractures may take longer to heal (14-24 weeks) and have a higher likelihood of developing osteomyelitis.⁶

A recent paper evaluating outcome after gunshot fractures in dogs noted a poor outcome in approximately half of cases, however, follow-up for many patients was lacking.⁷ Poor outcome in this paper was defined by delayed or non-union, paraparesis, vascular compromise, amputation, and peripheral neuropathy. Degree of soft tissue injury was the factor most closely associated with a poor outcome.

References

1. Capak H, Brkljaca Bottegaro N, Manojlovic A, Smolec O, Vnuk D. Review of 166 gunshot injury cases in dogs. Top Companion Anim Med. 2016;31(4):146-151. doi:10.1053/j.tcam.2016.11.001
2. Libardoni R do N, Serafini GMC, Oliveira C de, et al. Appendicular fractures of traumatic etiology in dogs: 955 cases (2004-2013). Cienc Rural. 2016;46(3):542-546. doi:10.1590/0103-8478cr20150219
3. Baum GR, Baum JT, Hayward D, MacKay BJ. Gunshot Wounds: Ballistics, Pathology, and Treatment Recommendations, with a Focus on Retained Bullets. Orthop Res Rev. 2022;14:293-317. doi:10.2147/ORR.S378278
4. Dougherty PJ, Sherman D, Dau N, Bir C. Ballistic fractures: indirect fracture to bone. J Trauma. 2011;71(5):1381-1384. doi:10.1097/TA.0b013e3182117ed9
5. Marecek GS, Earhart JS, Gardner MJ, Davis J, Merk BR. Surgeon preferences regarding antibiotic prophylaxis for ballistic fractures. Arch Orthop Trauma Surg. 2016;136(6):751-754. doi:10.1007/s00402-016-2450-8
6. Schwach RP, Park RD, Piermattei DL, Wingfield WE, Bartels KE. Gunshot fractures of extremities: classification, management, and complications. Vet Surg. 1979;8(3):57-62. doi:10.1111/j.1532-950X.1979.tb00609.x
7. Schrock K, Kerwin SC, Jeffery N. Outcomes and Complications Associated with Acute Gunshot Fractures in Cats and Dogs. Vet Comp Orthop Traumatol. 2022;35(3):205-212. doi:10.1055/s-0041-1739238