The Influence of Extrinsic Variation in Gunshot Wounds in a U.S. Civil War Skeletal Sample

Abstract

Most gunshot studies focus on the propagation of fractures on the cranium or the midshaft of a long bone. However, bone closer to the joint is structurally different from the shaft. Here, I analyzed the morphology of fracture patterns from gunshot wounds to the distal femora of U.S. Civil War soldiers. The individual sample (n=34) of distal femora was obtained from the Civil War Skeletal Collection at the National Museum of Health and Medicine (Silver Spring, MD). Variables collected included fracture counts, average fracture lengths, combined fracture lengths, location on the femur, registered age of the soldier, and their epiphyseal fusion status. The value in a U.S. Civil War skeletal sample is that the individuals it contains are relatively homogenous in terms of age, sex, ancestry, diet, and lifestyle. The projectiles involved were most commonly “minni balls;” many of which are preserved with the associated skeletal remains. Most of the variation in injury pattern is primarily related to extrinsic variables, such as distance from shooter, interruptions in projectile trajectory, and size, shape, or velocity of the impacting projectile at the time of contact. Intrinsic variables may still play a role, such as the amount of soft tissue present and impact location (indirect or direct contact). All measured individuals were male, with an average age of 24.18±6.84yrs. There was no correlation between age and combined fracture length. The average number of bone fragments and fractures counted were 3.59±2.89 and 7.26±3.94, respectively. The average fracture length was 44.80±19.95mm, with an average combined fracture length of 339.68±207.36mm. A limitation here is that these samples were collected via limb amputation, so some of the fractures extending proximally are incomplete. Interestingly, 7 individuals had an epiphyseal fusion score of 1 or 2 (with 4 being completely fused), with 2 instances in individuals aged 23 and 24yrs. In instances of unfused epiphyses, fractures that initiated in the epiphysis did not propagate into the diaphysis. The results of this study contribute to the understanding of how extrinsically introduced variation may affect what we see and interpret in gunshot wounds as more and longer fractures are usually associated with “higher velocity projectiles.” This study also noted the importance of epiphyseal fusion on ballistic analysis to long bones, but continued research is needed in this area to fully understand this phenomenon.