Prediction of hip and other osteoporotic fractures from hip geometry in a large clinical cohort

Incident hip fractures and non-hip osteoporotic fractures were studied in 30,953 women during mean 3.7 years of observation. Hip axis length (HAL) and strength index (SI) made a small but statistically significant contribution to hip fracture prediction that was independent of age and hip bone density. It is uncertain whether bone geometric measures improve fracture prediction independent of conventional areal bone mineral density (BMD). Women aged a parts per thousand yen50 years with hip dual-energy x-ray absorptiometry were identified from the regionally based database in the Province of Manitoba, Canada. Scans were reprocessed to derive parameters of hip bone geometry. Incident hip fractures (N = 270) and non-hip osteoporotic fractures (N = 1,347) were identified during mean 3.7 years of observation. HAL was greater in both hip and non-hip fracture cases than in non-fracture cases, whereas cross-sectional moment of inertia, cross-sectional area, and femoral SI were all significantly less. After adjustment for total hip BMD, HAL [hazard ratio (HR) 1.22 per SD increase, 95% CI 1.07-1.38] and SI (HR 1.21 per SD decrease, 95% CI 1.07-1.37) were independent predictors of hip fractures but not of non-hip fractures. When both HAL and SI were added to a model containing age and total hip BMD, there was a small improvement in hip fracture prediction (ROC area under the curve 0.832 +/- 0.013 vs 0.823 +/- 0.013; P = 0.001). HAL and SI made a small but statistically significant contribution to hip fracture prediction that was independent of age and BMD measurement.