Yield point in prediction of compressive behavior of lumbar vertebral body by dual-energy x-ray absorptiometry.

The aims of the present study were to evaluate the influence of bone mineral content (BMC) and density on the behavior of the lumbar vertebra during compression and to determine critical points during compression. Dual-energy X-ray absorptiometry (DXA) and compression tests were performed on 44 vertebral bodies obtained from 22 cadavers. The results of the study indicate that bone mineral content measured by DXA were strongly correlated with ultimate failure load (r = 0.53, p < 0.001), ultimate failure stress (r = 0.581, p < 0.001), and toughness (r = 0.632, p < 0.001). Correlation with the yield point (r = 0.543, p < 0.001) was also significant. Bone mineral density showed similar results with ultimate failure load (r = 0.742, p < 0.001), ultimate failure stress (r = 0.742, p = 0.001), toughness (r = 0.673, p < 0.001), and yield point (r = 0.693, p < 0.001). The correlation between elastic parameters and DXA were suggestive but not quite significant. BMC was not related significantly with stiffness or Young's modulus. There was no correlation between bone mass and vertebral deformation parameters. In conclusion, bone mass and bone density appear to have a clear relationship to ultimate parameters and yield point. The relation with the yield point might be critical because it marks the beginning of the plastic region and signals the appearance of the first trabecular fractures.