Role of superficial tissues, viscera, and the rib cage.

Three post-mortem human subjects were subjected to dynamic, non-injurious(nominal 20% chest deflection), anterior thoracic loading using a hub, a single diagonal belt, X-type double diagonal belts, and a distributed load. The test matrix also included three thoracic tissue conditions. First,the thoraces were tested intact. Second, they were tested in a "denuded"condition. For this condition, all tissue superficial to the rib cage (skin, fat, muscle) was removed. Finally, the thoraces were tested in an "eviscerated" condition. For this condition, the internal viscera (organs,vasculature, visceral fat etc) was removed. The intact thoraces were found to have significantly greater mean stiffness than the eviscerated or denuded thoraces (paired t-test p<0.05). The intact distributed (598.7 N/cm) and double-diagonal belt (529.2 N/cm) conditions were the stiffest, followed by the single diagonal belt (383.5 N/cm) then the hub (170.0 N/cm). The degree to which the soft tissues influenced the response depended on the loading condition. For the hub and distributed loading conditions, thedenuded thoraces were approximately 60% of the stiffness of the intact thoraces and the eviscerated thoraces were approximately 30%. The diagonal belt and X-type double diagonal belt loading conditions were not as sensitive to tissue condition. For those loading conditions, the denuded thoraces were approximately 85% of the intact stiffness and the eviscerated thoraces were approximately 55%. The findings of this study indicate the importance of the shoulder in the overall thoracic stiffness. The two loadingconditions that did not engage the shoulder (hub, distributed) were highly sensitive to the presence of the soft tissues of the thorax. In contrast, the two loading conditions that engage the shoulder were less sensitiveto the removal of the soft tissues. This study provides important validation data for thoracic models since the role of the bones, the organs, andthe superficial flesh has been quantified for multiple loading conditions. For the covering abstract see ITRD E134311.