Doctoral Dissertation Research: Exploring Localized Relationships Between Age-related Bone Loss and Cortical Expansion in Diaphyseal Bone

University Of Tennessee Knoxville, Knoxville TN

Investigators

Abstract

As humans age, the density of the mineral content of long bones declines, and bone geometry changes so that thickness of the bone wall decreases but overall diameter increases. It is expected that local mechanical loading from habitual activity will mediate both mineral loss and bone wall changes, which should be observable in comparisons of bone cross-sectional images between different bones. This doctoral dissertation project seeks to establish whether age-related changes in bone mineral density (BMD) and bone wall geometry co-occur locally within limb long bone cross-sections among living adults between 40-80 years of age. A localized relationship would suggest that geometric adaptation of bone to loading persists into advanced age despite overall loss of bone mass, which has implications for the interpretation of aging from archaeological contexts as well as for prevention of age-related fragility fractures. The project supports undergraduate and graduate training and research opportunities in STEM. In addition to scholarly dissemination of results in the form of conference presentations and journal publications, this research will be presented to project participants, as well as at public research forums, community centers, and other accessible settings. Age-related bone loss has been attributed to a host of interrelated systemic factors (e.g., hormone decline, loss of muscle strength) and is thereby treated as a global process throughout the body. With age, bone wall diameters expand and become thinner through the removal of bone from the internal surface and addition on the external surface. The resulting expansion of bone cross-sectional diameter bolsters resistance to bending under mechanical loads and, due to roughly concurrent timing with BMD decline, has been characterized as compensatory to bone loss. Earlier in life, bone wall geometry and microstructure adapt to mechanical loading. If this ability to adapt extends into late adulthood, it is possible that age-related wall expansion and BMD decline vary locally according to typical loading patterns within a bone cross-section, along the length of a bone, and between bone elements. If, in addition to local variation, results indicate that these processes exhibit local covariation, this research can provide further support to the compensatory relationship between the expansion of bone walls and BMD decline. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.