This NHTSA-sponsored study evaluated the response of five male cadaver torsos to quasi-static and dynamic anterior loading by rigid rectangular indentors designed to approximate a section of a shoulder belt. Indentor load and three-dimensional deflection measurements were recorded in order to quantify regional force-deflection and mechanical coupling of the anterior ribcage. Fractures were identified by post test necropsy. Dynamic loading produced higher forces than did quasi-static loading and the sternum was found to be stiffer than either the upper or lower loading ribcage sites for which similar stiffnesses were recorded. Rib fractures, many of which occurred at the costa-chondral junction, did not necessarily reduce the ability of the chest to resist anterior loading. The effects of rib fracture are most evident when loading the lower lateral rib cage and when there are many bicortical fractures. Bicortical fractures were more common for the older subjects whose ribcage cartilage was more calcified. The patterns of mechanical coupling were similar for different subjects, test conditions, and indentor compression levels. In most cases, the deflection toward the spine was greater than the lateral and inferior movement at any measurement site. In general, both the stiffness results and coupling patterns found in this study were similar to those previously reported for a prior benchmark study that used comparable methods. This study yields information required to develop computational and physical thorax models that exhibit improved biofidelic loading response.
Keywords: Ribcage; force-deflection; coupling; cadavers; rib fractures