A Densitometric Study of Mechanical Adaptation of Human and Nonhuman Primate Femoral Shafts

Abstract

The purpose of this study was to analyze the densitometric difference between human and nonhuman primate femoral shafts. A total of 37 femoral midshafts including 11 humans and 26 nonhuman primates were scanned by a computerized tomography (CT). Each of the obtained cross sections was divided into 8 regions corresponding to anatomical directions. Mean CT number and mean bone thickness for each region were calculated from the image data. Using these variables and the subperiosteal borders, coefficient of variation for bone density (CV), index of cross section (DI), index of bone thickness (TH), and index of bone density (DE) were derived and the relations among the indices were statistically analyzed. The mediolateral deviation of bone density in human femoral midshafts suggests a mechanical adaptation to bipedal locomotion. In nonhuman primates the correlation coefficient between DE and TH was higher than that between DE and DI. This implies an adaptive sequence from bone tissue level to cross-sectional shape, induced by mechanical stress.