Comparison of direct and indirect ballistic trauma to porcine femora: A contribution to the interpretation of patterns of skeletal trauma in conflict casualties

Abstract

Many types of skeletal trauma can be examined and identified on remains (blunt force, sharp force, ballistic, low-velocity projectile, sharp-blunt, thermal) and, due to the elastic and hardness properties of bone, each will present differently. Within ballistic trauma, there are further factors that will affect the visible patterns of trauma including the bone type, impact location and angle, and the shot distance. During humanitarian investigations, such as those carried out on casualties of the Spanish civil war, identification of the mechanism of trauma is essential when determining the manner and context of death for the individual. In order to do this studies must be conducted to provide comparison data for all factors affecting trauma. This study aims to contribute to the comparison data by examining the fracture and fragmentation patterns caused by the Mauser rifle by looking at direct and indirect impacts at varying shot distances. Twelve porcine femora were embedded in 20% ballistic gelatine and shot for direct and indirect impacts using 7.92mm Mauser ammunition at 10m and 20m distances. Once removed from the gelatine the size, shape, and edge characteristics of fragments were documented before reconstruction. The direct impacts presented with the (false) butterfly and double butterfly fracture patterns commonly seen in this type of trauma. Fragments from these bones showed semi-circular defects attributed to the entrance wound and edges consistent with peri-mortem trauma. Skimming impacts to the edge of the bone created elongated rectangular defects with fragments showing identifiable transverse edges. Indirect impacts showed simple fracture lines with no fragments but showed evidence of microfractures upon micro-CT scanning. Fragment analysis can be used to identify the mechanism of trauma in highly fragmented remains of humanitarian investigations; however, more research is needed to aid the identification of indirect ballistic trauma.