Femoral geometry, bone mineral density, and the risk of hip fracture in premenopausal women: a case control study

Background: The purpose of this study was to determine the relationships among hip geometry, bone mineral density, and the risk of hip fracture in premenopausal women. Methods: The participants in this case-control study were 16 premenopausal women with minimal-trauma hip fractures (fracture group) and 80 age-and BMI-adjusted controls. Subjects underwent dual-energy X-ray absorptiometry (DXA) to assess BMD at the proximal femur and to obtain DXA-derived hip geometry measurements. Results: The fracture group had a lower mean femoral neck and total hip BMD than the control group (0.721 +/- 0.123 vs. 0.899 +/- 0.115, p < 0.001 for the femoral neck BMD and 0.724 +/- 0.120 vs. 0.923 +/- 0.116, p < 0.001 for the total hip BMD). In addition, participants in the fracture group had a longer hip axis length (HAL; p = 0.007), narrower neck shaft angle (NSA; p = 0.008), smaller cross sectional area (CSA; p < 0.001) and higher cross sectional moment of inertia (CSMI; p = 0.004) than those in control group. After adjusting for BMD, the fracture group still had a significantly longer mean HAL (p = 0.020) and narrower NSA (p = 0.006) than the control group. Conclusions: BMD is an important predictor of hip fracture in premenopausal women. Furthermore, HAL and NSA are BMD-independent predictors of hip fracture in premenopausal women. Hip geometry may be clinically useful for identification of premenopausal women for whom active fracture prevention should be considered.