1School of Health Sciences, Cleveland State University, 2Department of Anatomical Sciences, Stony Brook University, 3Institute for Human Evolution, University of the Witwatersrand
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The primary orientation of trabecular bone (Tb) has been demonstrated empirically in vivo to develop in alignment with the direction of applied habitual load. This study tested the hypothesis that Tb morphology and orientation in skeletal ankle bones differs among hominoids in ways consistent with presumed differences in the habitual loads across the joint during life. The shape and primary orientation of Tb underlying the joint surfaces was digitally quantified in 9 subregions from micro-CT images of the distal tibia and talus (astragalus) of Homo, Pan, Gorilla, Pongo, and Papio. In both the distal tibia and talus, humans were found to have relatively greater Tb anisotropy and displayed overall more elongated Tb than the non-human hominoids, consistent with stereotypically predictable, sagittal-plane locomotion. In contrast, orangutans had overall more isotropic, less elongated Tb in the talus than the other species, and there were no significant differences found in Tb shape among regions, both results consistent with habitual loads that are more evenly distributed throughout the bone. The primary orientation of Tb was significantly different between humans and the non-human hominoids in the posterolateral and anteromedial regions of the talus, although not in the distal tibia. This study furthers understanding of the functional morphology of trabecular bone and its potential in inferring locomotor mode in isolated skeletal specimens.
This research was supported by grants from the NSF (BCS-1074079), the Wenner-Gren Foundation (Gr. 7930), and the Leakey Foundation.