In vivo assessment of the relation between trabecular bone structure in the radius and gender, aging, mechanical loading and fracture

Abstract

<p>Bone structure is compromised in individuals with osteoporosis. Indices of trabecular bone structure which reflect the connectivity (CI), the average dimensions of the marrow holes (HA ) and the area of the largest hole (HM ) at the distal radius can determined in vivo . This work evaluates whether these structural indices (1) are influenced by gender, aging and mechanical loading and (2) aid in the discrimination of individuals with low bone mass most at risk for fracture. Gender and age-related patterns of bone structure in the nondominant distal radius measured using peripheral quantitative computed tomography (pQCT) demonstrate the expected trends in a cross-sectional study of 145 healthy adults. Men have a better connected, less porous trabecular network. The age-related decrease in CI in men (-0.8%/yr, p < 0.05) is less pronounced than in women (-2.2%/yr, p < 0.001). Similarly, there are significant age-related increases in HA (+2.2%/yr, p < 0.01) and H M (+1.1%/yr, p < 0.01) in women but not in men. To investigate the impact of mechanical loading associated with hand dominance on indices of bone structure, bilateral images for 106 healthy adults were acquired. For all subjects, HM is significantly smaller in the dominant radius (p < 0.01). Right handed subjects (n = 96) have greater CI (p < 0.05) and smaller HM (p < 0.01) in the dominant limb. The effect of altered mechanical loading on bone structure was assessed by immobilizing the nondominant limb of 10 healthy volunteers in a plaster cast for 6 weeks followed by a remobilization period of 1 year. HM increases (p = 0.04) during immobilization and recovers within 3 months of remobilization. The ability of indices of trabecular structure to discriminate individuals with recent wrist fracture (n = 22) from controls matched for bone density (n = 22) was evaluated. The fracture group has a larger mean HA than the group without fractures (p < 0.05). The relative odds of wrist fracture is 6.9 (95% CI: 1.3 to 37.3) for individuals with a HA ≥ 6 mm2 . These data show that indices of trabecular bone structure, derived from pQCT images, reflect the expected patterns with respect to gender, age and mechanical loading. Preliminary results suggest that measuring HA at the distal radius may aid in the identification of individuals with low bone mass who will sustain a fracture.</p>