Cross-sectional geometry, bone strength, and bone mass in the proximal femur in black and white postmenopausal women

Osteoporosis is characterized by both a low bone mass and a disruption of t he architectural arrangement of bone tissue, leading to decreased skeletal strength and increased fracture risk, Although there are well-known ethnic differences in bone mass and fracture risk, little is known about possible ethnic differences in bone structure, Therefore, we studied cross-sectional geometry in the hip in a sample of postmenopausal black and white women in order to investigate ethnic differences that might contribute to differenc es in bone strength and ultimately hip fracture risk, We recruited 371 post menopausal black and white women who were entering the Women's Health Initi ative (WHI) clinical trials in Detroit, Bone density measurements of the pr oximal femur were done by dual-energy X-ray absorptiometry (DXA) using a Ho logic 1000 Plus bone densitometer. The DXA data were used for hip structure analysis, which treats the entire proximal femur as a continuous curved be am from the proximal shaft to the femoral neck, This permits the analysis o f cross-sectional geometric properties in two narrow regions corresponding to thin (5 mm) cross-sectional slabs seen on edge, The results indicate sig nificant ethnic differences in bone density, cross-sectional geometry, and dimensional variables, Specifically, the black women have a significantly h igher bone density in both locations (10.1% and 4.1% for the neck and shaft , respectively); greater cross-sectional geometric properties in the neck ( ranging from 6.1% to 11.6%), but a smaller endocortical diameter in the nec k (3.6%). There are fewer significant differences in cross-sectional geomet ry in the shaft location, Our data suggest that the spatial distribution of bone is arranged in the femoral neck to resist greater loading in black wo men compared with white women.