AGE-RELATED DIFFERENCES IN CROSS-SECTIONAL GEOMETRY OF THE FOREARM BONES IN HEALTHY WOMEN

Men exhibit age-related adaptive changes in long bone geometry, namely , endosteal resorption and periosteal apposition of bone, that help to preserve bone strength. It is not clear whether women undergo similar adaptive responses. To address this question, we assessed the bone mi neral density and cross-sectional geometry of the radius and ulna at t he one-third distal site by single photon absorptiometry and computed tomography (CT) in healthy young (n = 21, age 20-30 years) and older ( n = 22, age 63-84 years) women. We used the CT data to compute the tot al subperiosteal, medullary, and cortical areas, as well as the maximu m, minimum, and polar moments of inertia. We normalized the geometric parameters for bone length and performed comparisons using both the or iginal and size-corrected data. Radial and ulnar bone mineral content and density were 20-30% lower in the older women (P < 0.0001). Ulnar w idth, total area, medullary area, and maximum and polar moment of iner tia were greater in the older than in the younger women. Although we o bserved similar trends when we examined the radius data that were corr ected for bone size, age-related differences in radial geometry were l ess pronounced and were not significant. We conclude that women underg o endosteal resorption and periosteal apposition of the ulna with age, thereby exhibiting an adaptive pattern that helps to preserve bone st rength. The different behavior of these two bones suggests that local, rather than systemic, factors underlie this adaptation.