1Department of Anthropology, Pennsylvania State University, 2Center for Quantitative Imaging, Pennsylvania State University, 3McDonald Institute for Archaeological Research, University of Cambridge, 4Department of Anthropology, Ohio State University
Friday All day, Plaza Level
During human ontogeny, the initiation and eventual adoption of obligate bipedalism parallels a significant increase in body mass. These events dramatically alter the loads imposed on the lower limb skeleton throughout childhood and adolescence. The goal of this study is to examine the developmental trajectories of cortical and trabecular bone in the femur and tibia from birth to adulthood. High-resolution x-ray CT scans were collected for the femur and tibia of 70 individuals from the Norris Farms #36 skeletal collection ranging in age from neonate to adult. The entire bone was scanned with voxel dimensions less than 0.05mm. Cortical bone cross-sectional geometric properties were quantified at midshaft, and 3D trabecular bone structure was quantified for cubic volumes of interest extracted from the proximal femoral and tibial metaphyses. The results indicate that mid-diaphyseal cortical area (CA) and torsional and average bending strength (Z) follow broadly similar growth trajectories in the femur and tibia, continuing to increase until early adulthood. While the femoral midshaft remains primarily circular (Imax/Imin), the tibial midshaft becomes significantly more anteroposteriorly rigid during ontogeny. Trabecular structure displays a more complex pattern with most variables (BV/TV, Tb.Th, Tb.Sp, DA) following unique trajectories reflecting localized bone growth, (re)modeling processes, and joint kinematics that level off at adult values after approximately 10 years of age. These results indicate that while clearly interrelated, cortical and trabecular bone follow different growth trajectories in the femur and tibia, likely due to divergent biomechanical stimuli as well as different genetic mechanisms.
Grant support: NSF BCS-1028904 (TMR and JHG).