81 - Low to Moderate Correlation Between Localized Age-related Differences in Cortical Geometry and Bone Mineral Density

Poster Board Number: 81
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Co-authors:

Adam Sylvester - Johns Hopkins School of Medicine; Alice Gooding - Kennesaw State University; Dawnie Steadman - The University of Tennessee; Benjamin Auerbach - The University of Tennessee

Abstract Body : Age-related bone loss results in changes to both cortical bone geometry and microstructure, specifically increased cortical porosity and decreased bone mineral density (BMD). While these processes occur throughout the skeleton, local variation in age-related geometric changes has been observed both within and between cortical cross-sections of long bones. Local variation has also been noted in age-related changes to cortical BMD (cBMD). It is not clear, however, if age-related differences in cortical geometry and microstructure are spatially correlated. The purpose of this study is to assess correlation strength and direction in age-related differences in linear measures of cortical geometry and cortical BMD within and between cortical cross-sections of distal long bones.

A sample of 126 living individuals (78 females, 48 males) between 40-80 years of age was recruited to undergo peripheral quantitative computed tomography scanning of the tibia, radius, and ulna at 20%, 35%, 50%, and 65% tibial and forearm length. Eight directional radii originating from each cross-sectional centroid were established, and endosteal and periosteal semi-landmarks were placed where each radii intersects the endosteal and periosteal margin, respectively. Using these semi-landmarks, linear measurements of cortical thickness, endosteal distance to the centroid, and periosteal distance to the centroid were generated for each cross-section. Sectors of the cortical cross-section corresponding locally to these directional linear measurements were then sampled for cBMD. Age differences in geometric and cBMD measurements were calculated and Spearman’s rho correlation tests were performed to determine correlation strength and direction.

Results demonstrate low to moderate correlations between local age-related differences in cortical geometry and cBMD. The strongest correlations are observed between cBMD and endosteal distance to the centroid, while the weakest correlations are between cBMD and periosteal distance. These results suggest that local variation in age-related changes to cortical geometry and microstructure are not tightly coupled spatially as observed in a cross-sectional sample.