Zusammenfassung

A bone fractures only when loaded beyond its strength. The purpose of this study was to determine the association of femoral strength, as estimated by finite element (FE) analysis of DXA scans, with incident hip fracture in comparison to hip BMD, FRAX® and hip structure analysis (HSA) variables. This prospective case-cohort study included a random sample of 1941 women and 668 incident hip fracture cases (295 in the random sample) during a mean±SD follow-up of 12.8±5.7 yrs from the Study of Osteoporotic Fractures (n=7860 community-dwelling women ≥67 yr of age). We analyzed the baseline DXA scans (Holgoic 1000) of the hip using a validated plane-stress, linear-elastic finite element (FE) model of the proximal femur and estimated the femoral strength during a simulated sideways fall. Cox regression accounting for the case-cohort design assessed the association of estimated femoral strength with hip fracture. The age-BMI-adjusted hazard ratio (HR) per SD decrease for estimated strength (2.21, 95% CI 1.95–2.50) was greater than that for TH BMD (1.86, 95% CI 1.67–2.08; p<0.05), FN BMD (2.04, 95% CI 1.79–2.32; p>0.05), FRAX® scores (range 1.32–1.68; p<0.0005) and many HSA variables (range 1.13–2.43; p<0.005), and the association was still significant (p<0.05) after further adjustment for hip BMD or FRAX® scores. The association of estimated strength with incident hip fracture was strong (Harrell's C index 0.770), significantly better than TH BMD (0.759, p<0.05) and FRAX® scores (0.711–0.743, p<0.0001) but not FN BMD (0.762, p>0.05) Similar findings were obtained for intra- and extra-capsular fractures.