Black-White Differences in Hip Geometry

Previous studies have demonstrated that reduced thickness of the femoral neck and shaft cortex, a wider intertrochanteric region and a longer hip axis length were predictive of hip fracture among Caucasian women. We hypothesized that racial differences in these features of hip geometry may contribute to explaining the differences in hip fracture incidence between women of African origin and Caucasian women. We measured the cortical thickness and bone widths in 132 African-American women and 43 Nigerian women who were pair-matched on height (± 3 cm), age (± 5 years) and weight (± 3 kg) to 175 Caucasian women. Measures of cortical thickness were greater among women of African origin than Caucasian. Women of African origin had smaller bone widths and a shorter hip axis length than Caucasians. Several of these differences were independent of bone mineral density except for the cortical thickness of the femoral shaft. We conclude that women of African origin have thicker cortical bone of the hip, a shorter hip axis length and smaller intertrochanteric widths than Caucasians. Based on a model developed from hip fractures among Caucasian women, we predict that these observed racial differences could contribute to approximately a 25% decrease risk of hip fracture among blacks.