Vascular Structure and Elastic Anisotropy in Cortical Bone

Elastic properties define the relationship in cortical bone between loading and deformation. Our investigations show the considerable variations in 3D elastic properties in the craniofacial skeleton, in particular, the variations in anisotropy as indicated by the ratio of elastic modulus between the axes of minimum and maximum stiffness within the cortical plane. These variations are an important but generally overlooked aspect of bone quality. Continuing studies are testing whether variations in cortical elastic anisotropy correlate with variations in 3D osteonal structure. A positive correlation would lend support to the claim that 3D osteonal structure is influenced by the orientation of mechanical loads in cortical bone. In the majority of midfacial cortical bone specimens, average osteon orientation weighted by osteon length is within 15 degrees of the direction of maximum stiffness. The anisotropy ratios are moderately correlated with the standard deviation of osteon orientation with R values of about 0.50. Results suggest that osteon orientation is a structural correlate of cortical anisotropy. However, the moderate correlations suggest that other factors, such as collagen orientation, or the quantity and structure of primary bone, are likely also important in determining cortical bone anisotropy at a supraosteonal or bulk level of organization. Supported by NSF BCS‐0240865.