Variation of human cancellous bone ultrasonic properties with density and micro-structure

The present study was designed to investigate the relationships between ultrasonic properties, density and micro-architecture of cancellous bone. The slope of the frequency-dependent attenuation coefficient, the speed of sound and the frequency-averaged backscatter coefficient were measured in 25 cylindrical cancellous bone cores. Bone mineral density was determined using X-ray quantitative computed tomography. Microarchitecture was investigated with synchrotron radiation with an isotropic spatial resolution of 10 /spl mu/m. Several microstructural parameters reflecting the morphology, the connectivity and the anisotropy of the specimens were derived from the reconstructed 3D micro-architecture. The association of the ultrasonic variables with density and micro-architecture was assessed using simple and multivariate linear regression techniques. Variables directly reflecting the amount of bone tissue explained most of the variance of the ultrasonic properties (r/sup 2/ ranging from 70% to 80%) and the additional variance explained by microstructural parameters was small (/spl Delta/r/sup 2/<6% at best). In particular, no significant independent association existed between microstructure and backscatter coefficient (a micro-structure related ultrasonic parameter) after adjustment for density. These results may be attributed to the strong covariance effect between micro-architecture and density.