Biomechanics of abdominal injuries by armrest loading

Anesthetized pigs were exposed to impact against a padded side interior that included an armrest with either a SOFT or STIFF crush characteristic. The purpose was to assess liver and spleen injury under specific impact conditions. The STIFF armrest resulted in severe abdominal and thoracic injury in five side-impact animal tests. Injuries of the liver and spleen included deep lacerations, tears of major hepatic arteries and veins, and serious hemoperitoneum. The injuries averaged AIS = 4. In contrast, five animals exposed to the SOFT armrest design experienced injuries of lower severity than any animal in the STIFF armrest exposures (p < 0.005). The average injury was AIS = 2. The STIFF armrest protruded into the abdomen and showed little sign of deformation with abdominal loading. This situation is consistent with the occurrence of lacerations at hepatic junctions and between lobes, and displaced rib fractures in several cases. The SOFT armrests crushed fully in each test, indicating that abdominal compression was lower and was limited by armrest deformation.