Strength prediction of the distal radius by bone densitometry--evaluation using biomechanical tests

Osteoporotic fractures represent an important medical problem as they are often early predictors of future fractures at other skeletal sites. The distal radius is one such fracture site. To determine the individual's risk of fracture, different measurement techniques have been developed. These methods differ in physical background, measurement site, output parameters, and cost. If correctly applied, biomechanical testing can be an efficient tool for the preclinical evaluation of these techniques. With biomechanical testing it is possible to determine the structural strength of bone which can then be correlated with various densitometric parameters. Here we will review experimental work performed in this context. Biomechanical testing conditions vary considerably from study to study with 3-point bending (shaft), axial compression (metaphysis), and fall simulations being some of the techniques used. Experimental evidence suggests that site-specific osteodensitometric measurements can predict the mechanical strength of the distal radius with moderate to high accuracy, but that measurements at remote sites display considerably lower predictive value. Geometry-based parameters of cortical bone are also good predictors, but have not been shown to offer significant advantage over measurement of bone mass. Some (but not all) studies have found that quantitative ultrasound and microstructural parameters contribute significant additional information to bone mass measurement. The most accurate prediction of distal radius fractures, however, appears to be (patient-specific) microstructural finite element modeling.