Evaluation of bone surrogates for indirect and direct ballistic fractures

• Two surrogates (Sawbones and Synbones) were evaluated as bone surrogates for ballistic testing.
• Neither surrogate reproduced fracture patterns similar to those seen with cadaveric bone.
• Fracture patterns could only be matched with varying velocities of direct impact.
• The Synbone surrogate did have a similar distance from bone for indirect fracture as cadaveric bone.

The mechanism of injury for fractures to long bones has been studied for both direct ballistic loading as well as indirect. However, the majority of these studies have been conducted on both post-mortem human subjects (PMHS) and animal surrogates which have constraints in terms of storage, preparation and testing. The identification of a validated bone surrogate for use in forensic, medical and engineering testing would provide the ability to investigate ballistic loading without these constraints. Two specific bone surrogates, Sawbones and Synbone, were evaluated in comparison to PMHS for both direct and indirect ballistic loading. For the direct loading, the mean velocity to produce fracture was 121 ± 19 m/s for the PMHS, which was statistically different from the Sawbones (140 ± 7 m/s) and Synbone (146 ± 3 m/s). The average distance to fracture in the indirect loading was .70 cm for the PMHS. The Synbone had a statistically similar average distance to fracture (.61 cm, p = 0.54) however the Sawbones average distance to fracture was statistically different (.41 cm, p < 0.05). Fractures patterns were found to be comparable to the PMHS for tests conducted with Synbones, however the input parameters were slightly varied to produce similar results. The fractures patterns with the Sawbones were not found to be as comparable to the PMHS. An ideal bone surrogate for ballistic testing was not identified and future work is warranted.