HUMAN VERTEBRAL CANCELLOUS BONE SURFACE DISTRIBUTION

The three-dimensional distribution of bone surface and the bone volume fraction (BV/TV) of 110 human vertebral cancellous bone specimens fro m seven individuals were measured using a three-dimensional radiograph ic method (microcomputed tomography). The ratios of the three principa l projections of bone surface per total volume were found to be relati vely constant for specimens examined in this study. The constancy of t he projected surface ratios means that the fraction of the total bone surface oriented in any direction does not change markedly with BV/TV. Bone volume fraction was a good predictor of bone surface per total v olume (BS/TV) for a one-parameter nonlinear model (r(2) = 0.92). The r esults of this pilot study suggest that the changes in surface distrib ution which occur during age-related bone loss are largely predetermin ed rather than adaptive. The results are also consistent with the idea that cancellous bone tends to maintain a constant ratio of trabecular number for the principal directions. If these inferences from the dat a are correct, the morphogenetic processes which create the initial ad ult trabecular pattern become of primary interest. A model was develop ed which explained the strong relationship between BS/TV and BV/TV. Th e model was used to demonstrate the importance of morphogenetic proces ses.