Bone Mineral Density of the 1/3 Radius Refines Osteoporosis Diagnosis, Correlates With Prevalent Fractures, and Enhances Fracture Risk Estimates.

OBJECTIVE

To investigate the added value of 1/3 radius (1/3R) for the diagnosis of osteoporosis by spine and hip sites and its correlation with prevalent fractures and predicted fracture risk.

METHODS

Fracture Risk Assessment Tool (FRAX) scores for hip and major osteoporotic fractures (MOF) with/without trabecular bone score were considered proxy for fracture risk. The contribution of 1/3R to risk prediction was depicted via linear regression models with FRAX score as the dependent variable-first only with central and then with radius T-score as an additional covariate. Significance of change in the explained variance was compared by F-test.

RESULTS

The study included 1453 patients, 86% women, aged 66 ± 10 years. A total of 32% (n = 471) were osteoporotic by spine/hip and 8% (n = 115) by radius only, constituting a 24.4% increase in the number of subjects defined as osteoporotic (n = 586, 40%). Prior fracture prevalence was similar among patients with osteoporosis by spine/hip (17.4%) and radius only (19.1%) (P = .77). FRAX prediction by a regression model using spine/hip T-score yielded explained variance of 51.8% and 49.9% for MOF and 39.8% and 36.4% for hip (with/without trabecular bone score adjustment, respectively). The contribution of 1/3R was statistically significant (P < .001) and slightly increased the explained variance to 52.3% and 50.4% for MOF and 40.9% and 37.4% for hip, respectively.

CONCLUSION

Reclassification of BMD results according to radius measurements results in higher diagnostic output. Prior fractures were equally prevalent among patients with radius-only and classic-site osteoporosis. FRAX tool performance slightly improved by incorporating radius BMD. Whether this approach may lead to a better fracture prediction warrants further prospective evaluation.