Contribution of quantitative ultrasound measurements to fracture risk assessment

Abstract

Osteoporosis is a silent disease as patients are often unaware of their condition until a fracture occurs. Thus, early detection and identification of at-risk individuals are essential. Although bone mineral density (BMD) testing is the “gold standard” for fracture risk assessment, a substantial proportion of fracture cases remain unexplained by BMD. Quantitative ultrasound (QUS) with its potential to measure both bone density and structure may offer additional information in identifying at-risk individuals. Meanwhile, both osteoarthritis (OA) and obesity are associated with high BMD, but their relationships with fracture risk are still unclear. Therefore, the primary aims of this thesis are: (1) to evaluate the contribution of QUS to fracture risk assessment, with particular emphasis on individuals without low BMD; and (2) to determine the association between OA or body mass index (BMI) and fracture risk in relation to BMD. Using prospective data from the Dubbo Osteoporosis Epidemiology Study (DOES), it was found that calcaneal QUS was significantly associated with fracture risk, independent of BMD in women with or without osteoporotic BMD. More importantly, a combination of broadband ultrasound attenuation (BUA) and BMD can improve the prediction of fracture risk by 7.3% in women. However, the fracture predictability of QUS seems to be device-specific, as QUS measured by a multisite device was not predictive of fracture risk in both men and women. Although higher BMI was found to be associated with lower fracture risk, its protective effect against fracture was largely mediated by BMD. The overall mediated effect estimates were -0.048 (95% CI, -0.059 to -0.036; p<0.001) in women and -0.030 (95% CI, -0.042 to -0.018; p<0.001) in men. Higher BMI is also associated with OA. However, women with OA were 50% more likely to experience a fragility fracture than their non-OA counterparts. These results suggest that calcaneal QUS is a useful tool for improving fracture risk assessment, particularly in women without low BMD. The finding of a positive association between OA and fracture risk may contribute to explaining the occurrence of fragility fracture in the non-osteoporotic population.