Assessment of fracture risk by bone density measurements.

Bone densitometry in its various applications has become an established tool for the diagnosis of osteoporosis. Bone density has been shown to be significantly associated with the risk of future fracture in many prospective studies. From long-term prospective studies, it can be concluded that peak bone density and bone loss are important predictors of subsequent fracture, and that fracture can be predicted over a longer period. Bone density predicts fracture even in elderly persons aged 80 years and older. However, in this population some fractures, such as the cervical hip fracture, may be more strongly influenced by other risk factors. The differences between the various densitometric techniques in predicting future osteoporotic fracture of any type is marginal. However, it seems that bone density measurements at the site of fracture do perform better than measurements at other sites. There is no evidence that measuring a second site improves the diagnostic capability of bone densitometry. The association between bone density and future fracture is partly independent of age and other significant predictors of fracture such as falls, cognizance, and mobility. Quantitative ultrasonic measures of bone quality have been shown to have a predictive capability that is comparable to that of bone density. From the perspective that bone densitometry and quantitative ultrasound independently predict fractures, these measures actually seem complementary rather than competitive. Simple geometric measures of the bones such as hip axis length and vertebral depth may be derived from images of bone densitometry scans and are also predictive of hip fracture or vertebral fracture independently of bone density. Using the current knowledge of the association between bone density, quantitative ultrasound, geometric properties, and fractures as well as clinical risk factors, new models for fracture prediction can be developed for future application in clinical practice for the benefit of the individual patient.