EFFECTS OF POSTMORTEM DEGRADATION ON THE TENSILE MATERIAL PROPERTIES OF BOVINE LIVER PARENCHYMA

摘要

Although the liver is one of the most frequently injured organs in motor vehicle collisions (MVCs), none of the currently accepted anthropomorphic test devices are able to predict abdominal organ injury risk. Consequently, finite element models are becoming an integral tool for assessing abdominal organ injury risk in MVCs. However, these models must be validated based on biomechanical data. Although previous studies have quantified the tensile material properties of liver parenchyma, there have been no studies that have evaluated the effect of postmortem degradation on the failure properties occurring within the first 24 hours of death. The purpose of this study was to quantify the effects of postmortem degradation on the tensile material properties of bovine liver parenchyma between 6 and 48 hours after death. Uniaxial tension tests were conducted on the parenchyma of seven bovine livers acquired from a local slaughterhouse immediately after death. Tissue was immersed in Dulbecco's Modified Eagle Medium and kept cool (i.e., never frozen) during preparation and storage. Multiple "dog-bone" specimens from each liver were tested once to failure at three time points: ～6hrs, ～24hrs, and ～48hrs after death. The data were analyzed to determine if there were significant changes in the failure stress and failure strain with respect to postmortem time. The average failure stresses were 37.3±15.1kPa, 40.4±12.1kPa, and 36.0±11.3kPa at the 6hr, 24hr, and 48hr time points, respectively. The average failure strains were 0.24±0.044, 0.22±0.026, and 0.25±0.041, at the 6hr, 24hr, and 48hr time points, respectively. There were no statistical differences in failure stresses or failure strains between time points. The results show that the failure stress and strain of bovine liver parenchyma do not change significantly between 6 hours and 48 hours after death when stored in DMEM and kept cool. Overall, this study elucidates the effects of postmortem degradation on the material properties of liver parenchyma.