Prediction of hip osteoporotic fractures from composite indices of femoral neck strength

To clarify whether composite hip strength indices improve predictive ability for hip osteoporotic fractures independent of conventional bone mineral density (BMD). Three hundred and eighty-two health controls and 43 women with hip fractures (aged 28.2-87.7 years, mean age 59.5 +/- 9.2 years) were measured by dual energy X-ray absorptiometry for femoral neck bone mineral density (FN_BMD) and proximal femur geometry parameters of hip, and composite hip strength indices (Compression strength index, Bending strength index, and Impact strength index). The association between the studied parameters and the fractures was modelled using multiple logistic regression, including age, height, weight, and menopausal status. Fracture-predicted probability was calculated for each predictor tested. ROC curve areas (AUCs) were calculated for the fracture status, having the calculated fracture-predicted probability as a test variable. AUCs were compared by the Hanley-McNeil test. Women with hip fractures had lower FN_BMD, composite hip strength indices, and longer hip axis length than controls, and no significant difference in femoral neck width. Logistic regression showed composite hip strength indices could predict hip fractures risk. To the same extent as FN BMD, Compression Strength Index (CSI) best predicted the risk for each fracture (AUC = 0.787 +/- 0.028). When CSI was added to FN_BMD, there was a small but not statistically significant increase in AUC to 0.796 +/- 0.027 (P = 0.9018). Composite indices of femoral neck strength may be valuable in the assessment of the biomechanics of bone fragility; however, they do not appear to add diagnostic value to the simple measurement of BMD.