The 82nd Annual Meeting of the American Association of Physical Anthropologists (2013)


Ontogenetic changes in the human tibial and femoral diaphyses: Mechanobiological analysis of cortical shape from a whole-bone perspective

ZACHARIAH R. HUBBELL1, JAMES H. GOSMAN1, COLIN N. SHAW2 and TIMOTHY M. RYAN3,4.

1Department of Anthropology, The Ohio State University, 2McDonald Institute for Archaeological Research, Cambridge University, 3Department of Anthropology, Pennsylvania State University, 4Center for Quantitative Imaging, EMS Energy Institute, Pennsylvania State University

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It is well-established that cortical bone geometry of weight-bearing bones is in part related to mechanical loading history. During ontogeny, load patterns shift in association with growth and gait maturation, resulting in changing bone morphology. We test the hypothesis that ontogenetic patterns of cross sectional cortical shape change in the human femoral and tibial diaphyses are age- and anatomical site-specific. Femora (n=46) and tibiae (n=47) ranging developmentally from neonatal to skeletally mature were obtained from the Norris Farms No. 36 skeletal series, an Oneota Native American assemblage (ca. A.D. 1300). Whole bones underwent high resolution x-ray CT scanning at the Pennsylvania State Center for Quantitative Imaging with size-specific resolutions ranging from 0.013 to 0.094 mm. Whole-diaphysis cortical drift patterns and relative bone envelope modeling activity across ages were assessed in five locations per bone (20, 35, 50, 65, and 80% of total bone length) by measuring the distance from the section centroid to the endosteal and periosteal margins in eight sectors in ImageJ. Changes in the periosteal/endosteal surfaces and cortical width were recorded for each diaphyseal slice. Correlation between age and the ratio of maximum to minimum bending rigidity (Imax/Imin) was tested at each slice location. Results show that cortical shape changes are most strongly associated with age in the femoral extremities (20 and 80%) and tibial proximal diaphysis (80%), indicating that these locations may be more sensitive to developmental mechanical load shifts than the midshaft. These findings highlight the utility of additional anatomical locations for bioarchaeologists investigating physical activity.

Grant Sponsor: NSF grant number BCS-1028799 (JHG and TMR)

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