Associations between bone material strength index and FRAX scores

Impact microindentation (IMI) measures bone material strength index (BMSi) in vivo. However, its ability to predict fractures is still uncertain. This study aimed to determine the association between BMSi and 10 year fracture probability, as calculated by the FRAX algorithm.

BMSi was measured using the OsteoProbe in 388 men (ages 40-90 yr) from the Geelong Osteoporosis Study. The probabilities for a major osteoporotic fracture (MOF) and hip fracture (HF) were calculated using the Australian FRAX tool. Hip (HF) and major osteoporotic (MOF) fracture probabilities were computed with and without the inclusion of femoral neck bone mineral density (BMD). For each participant, four 10 year probability scores were therefore generated: (i) HF-FRAXnoBMD; (ii) HF-FRAXBMD; (iii) MOF-FRAXnoBMD; (iv) MOF-FRAXBMD.

BMSi was negatively correlated with age (r = - 0.114, p = 0.025), no associations were detected between BMSi and femoral neck BMD (r = + 0.035, p = 0.507). BMSi was negatively correlated with HF-FRAXnoBMD (r = - 0.135, p = 0.008) and MOF-FRAXnoBMD (r = - 0.153, p = 0.003). These trends held true for HF-FRAXBMD (r = - 0.087, p = 0.094) and MOF-FRAXBMD (r = - 0.111, p = 0.034), but only the latter reached significance.

BMSi captures the cumulative effect of clinical risk factors in the FRAX algorithm, suggesting that it could provide additional information that may be useful in predicting risk of fractures. Further studies are warranted to establish its efficacy in predicting fracture risk.