TRABECULAR BONE-MINERAL AND CALCULATED STRUCTURE OF HUMAN BONE SPECIMENS SCANNED BY PERIPHERAL QUANTITATIVE COMPUTED-TOMOGRAPHY - RELATION TO BIOMECHANICAL PROPERTIES

The relationship of cortical bone mineral density (BMD), and geometry to bone strength has been well documented. In this study, we used peri pheral quantitative computerized tomography (pQCT) to acquire trabecul ar BMD and high-resolution images of trabeculae from specimens to dete rmine their relationship with biomechanical properties. Fifty-eight hu man cubic trabecular bone specimens, including 26 from the vertebral b odies, were scanned in water and air. Trabecular structure was quantit ated using software developed with Advanced Visual Systems interfaced on a Sun/Sparc Workstation. BMD was also obtained using a whole-body c omputerized tomography scanner (QCT). Nondestructive testing of the sp ecimens was performed to assess their elastic modulus. QCT and pQCT me asurements of BMD of specimens in water were strongly correlated (r(2) = 0.95, p < 0.0001), with a slope (0.96) statistically not significan tly different from 1. Strong correlations were found between pQCT meas urements of specimens in water and in air,for BMD (r(2) = 0.96, p < 0. 0001), and for apparent trabecular structural parameters (r(2) = 0.89- 0.93, p < 0.0001). Correlations were moderate between BMD and apparent trabecular structural parameters (r(2) = 037-0.64,p < 0.0001). Precis ion as coefficient of variation (CV) and standardized coefficient of v ariation (SCV) for these measurements was < 5%. For the vertebral spec imens, the correlation was higher between elastic modulus and BMD (r(2 ) = 0.76, p < 0.0001) than between elastic modulus and apparent trabec ular structural parameters (r(2) = 0.58-0.72, p < 0.0001), while the a ddition of apparent trabecular nodes and branches to BMD in a multivar iate regression model significantly increased the correlation with the elastic modulus (r(2) = 0.86, p < 0.01). Thus, pQCT can comparably an d reproducibly measure trabecular bone mineral in,vater or air, and tr abecular structure can be quantitated from pQCT images. The combinatio n of volumetric BMD with trabecular structural parameters rather than either alone improves the prediction of biomechanical properties. Such a noninvasive approach may be useful for the preclinical study of ost eoporosis.