Variation in young ovine cortical bone properties in regions habitually exposed to tension versus compression
Keywords:Bone mineral density, Cortical, growth, mechanical properties, thickness
Significant effort continues to be made to understand whether differences exist in the structural, com- positional, and mechanical properties of cortical bone subjected to tensile vs. compressive loading. We evaluated juvenile sheep femora (age = 4 months) from the anterior (tensile) and posterior (compres- sive) quadrants at three points along the diaphysis. MicroCT scans (50 micron) were used to measure cortical thickness and mineral density. Three point bending tests were performed to measure the flex- ural modulus, strength, and post-yield displacement. There was no difference in cortical thickness between tensile and compressive quadrants; however, density in the tensile quadrant was higher than the compressive quadrant in the proximal and middle diaphysis. Modulus and strength was higher in the tensile quadrant than in compressive regions. Together, our results suggest that there is a differential response of bone to historical tensile vs compressive loading in terms of elastic bending modulus and mechanical strength. The origins of this difference may lie within the variation in mineral density we observed between the two regions. However, the role of the constituent components of bone still undergoing mineralization, in combination with the plexiform structure, remains to be explored. This data suggest that in young ovine cortical bone, modulation of strength occurs via increased mineralization in regions exposed to tension thereby providing a possible biomechanical target for exercise prescriptions.
Copyright (c) 2022 Sony Manandhar, Sara Moshage, Joshua Craggette, John Polk, Mariana Kersh
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