The purpose of this research was to establish the biomechanical response of the upper human abdomen to blunt ballistic impacts and to determine appropriate injury predictors for liver and bowel injuries.

Unembalmed, post-mortem human subjects (PMHS) were used to establish the biomechanical response corridors for the upper abdomen. The epigastric and right hypochondriac regions of the PMHS were tested using a 45 gram, instrumented projectile launched into the abdomen at a target velocity of 60 m/s. Impact force and abdominal compression were used to establish biomechanical response corridors. The epigastric corridor was characterized by an initial mean stiffness of 445±72 kN/m and a mean peak force of 3,298±323N. The initial mean stiffness of the right hypochondriac corridor was 484±72 kN/m and the mean peak force was 3,684±412 N.

Seventeen anesthetized Yorkshire Cross swine weighing 44±2 kg were used to study the injury risk associated with less lethal projectile impacts to the abdomen. The porcine subjects were impacted in the epigastric, left lumbar and right lumbar regions of the abdomen. The subjects were euthanized shortly after the testing and necropsies performed to document the resulting injuries. Injuries were coded using the Abbreviated Injury Scale (AIS). Liver injuries were also coded using the Organ Injury Scale (OIS).

Univariate logistic regression analysis was used to determine appropriate predictors of AIS/OIS≥2 liver and AIS≥2 bowel injuries. The best predictors of liver injury, rated by the AIS scale, were maximum force and BC. The best predictors of OIS liver injuries were BC, maximum force and maximum AIC. The best predictors of bowel injury were maximum energy dissipated and impact velocity.

The effect of impact velocity on biomechanical response was evaluated for the porcine testing. The results of ANOVA analyses indicated that for abdominal impact velocities ranging from 35 – 75 m/s, impact velocity has no statistical effect on the stiffness of the porcine abdomen. Further, it was determined that there was no statistical difference between the abdominal stiffness values found across the three impact regions. The biomechanical response of the porcine abdomen to less lethal impacts is characterized by an initial mean stiffness of 1,107±234 kN/m and the mean peak force for abdominal impacts was correlated with impact speed.

The epigastric mean stiffness value obtained from the PMHS was compared with that obtained from the porcine tests. T-test results indicated there was a significant difference between the PMHS and porcine response.