Normalized BMD as a predictor of bone strength.

Abstract

RATIONALE AND OBJECTIVES: In the noninvasive evaluation of bone quality, bone mineral density (BMD) has been shown to be the single most important predictor of bone strength and osteoporosis-related fracture. Among the methods of measuring BMD, dual x-ray absorptiometry (DXA) has widespread acceptance due to its low radiation, low cost, and high precision. However, DXA measures area BMD instead of true volumetric density; thus, a larger bone will tend to have a high BMD than will a smaller bone. Therefore, the comparison of BMDs of bones of different sizes can be misleading. In this study, the authors tried to compensate for the size effect by normalizing the area BMD with bone size as measured from a standard pelvic radiograph. MATERIALS AND METHODS: The overall method for calculation of normalized BMD included conventional area-based BMD from DXA and the extraction of geometric measures from pelvic radiographs. The database for analysis included 34 femoral neck specimens. Regression analysis was performed between the normalized volumetric BMD, measured from femoral neck region, and the mechanical properties obtained from trabecular bone cubes machined from the same region. RESULTS: After normalization of the area BMD, the coefficient of determination increased from 0.30 to 0.43 for the Young modulus and from 0.27 to 0.37 for bone compressive strength. CONCLUSION: A noninvasive method of normalizing BMD can improve the prediction of bone mechanical properties and has potential in monitoring changes in growing skeletons and in the clinical evaluation of bone quality.