Bone strain index improves 10-year fracture risk prediction beyond bone mineral density and FRAX® in community-dwelling older women: A study of the FRISBEE cohort.

Abstract

The Bone Strain Index (BSI), derived from finite element analysis of DXA, quantifies mechanical strain within bone. Its predictive value for fragility fractures in older women remains to be established in large prospective studies. This prospective cohort study assessed the association between BSI, incident fragility and major osteoporotic fractures (MOF) in 3338 community-dwelling older women (age 64-77 years) during a 5-year and 10-year follow-up. BSI was calculated at the lumbar spine, total hip, and femoral neck using baseline DXA scans. Incident fragility and MOF were radiographically validated. Discriminative performance was assessed using ROC curves, optimal cut-offs (Youden index), and Cox proportional-hazards models adjusted for age, areal bone mineral density (aBMD), or FRAX® score. During the 10-year follow-up, 803 women (24.1%) sustained at least one fragility fracture, including 525 MOF. Higher BSI values were significantly associated with increased fracture risk at 5 and 10 years, independently of age, aBMD, or FRAX®. Total hip BSI showed the strongest performance among all sites (AUC 0.63 at 5 and 10 years), outperforming lumbar spine BSI (AUC 0.58). Each 1-SD increase in total hip BSI was associated with higher fracture risk (HR 1.42 [1.32-1.53] at 5 years; 1.41 [1.34-1.49] at 10 years), which remained significant after FRAX® adjustment (HR 1.24 [1.14-1.35]). BSI independently predicted incident fragility fractures and MOF during a 5-year and 10-year follow-up in a large cohort of community-dwelling older women. Total hip BSI showed stronger predictive performance than lumbar spine BSI, and both provided discriminative value beyond aBMD and FRAX®.