Evaluation of an In Situ Ovine Model as a Surrogate for Human Skin Injury Caused by High-Rate Blunt Impact

Abstract

Understanding the risk of skin injury caused by impacts from blunt less lethal weapons (LLW) is critical for designing safer devices, but the tolerances of injury are still understudied. Previous research has utilized post-mortem human surrogates (PMHS) to investigate the injury thresholds of various soft tissues; however, PMHS testing is often limited by low sample size and questions surrounding the biofidelity of the tissue for approximating the living response. Animal surrogates are often used to supplement these known limitations. In this study, eight in situ ovine specimens were tested under high-rate, blunt impacts to assess the viability of this model as a surrogate for human skin. All tests were conducted using a 6.5 g, 19 mm (0.75 in.) diameter cylindrical impactor with impact velocities up to 162 m/s. Injury assessments were performed to study the effect of body region, tissue storage condition, and flesh temperature on the likelihood of skin injury. Injury risk functions (IRFs) were developed relating skin injury risk to impactor velocity and the impacted body region. Impact location was a significant factor for injury risk, with the tissues in the shoulder and ribs demonstrating lower tolerances for skin injury than in the stomach and rump. By the comparing IRF responses to that of PMHS, the cadaveric ovine tissue showed viability as a potential surrogate for human skin (from the upper chest and abdomen regions) under high-rate blunt impacts. Furthermore, there were no significant differences in IRFs produced with fresh and frozen-thawed tissue. Anecdotally, variation in flesh temperature produced different injury results, but statistically this effect was insignificant due to the limited sample size of the study.