Relationships between densitometric and morphological parameters as measured by peripheral computed tomography and the compressive behavior of lumbar vertebral bodies from Macaques (Macaca fascicularis)

Study Design. The measured maximum compressive force and stress of lumbar vertebral bodies from cynomolgus monkeys were compared with peripheral quantitative computed tomography (pQCT) derived densitometric and morphologic vertebral parameters. Objectives. To determine, which pQCT parameters were predictive of vertebral mechanical behavior, and of these, identify those that were the best predictors of vertebral load capacity. A secondary objective was to test the suitability of a multiple parameter-based approach for predicting vertebral mechanical load response. Summary of Background Data. Noninvasive methods for identifying and diagnosing changes in skeletal load tolerance are imperative for early detection of bone diseases such as osteoporosis. It is currently unclear, which densitometric and morphologic parameters are the best predictors of the mechanical performance of bone tissues. Methods. Seventy-seven monkey lumbar vertebrae from the species Macaca fascicularis were tested. Following midbody cross-sectional pQCT scans of each specimen, specimens were loaded in axial compression until failure. The pQCT parameters were evaluated independently for correlation with the mechanical response of the vertebral bodies. The parameters were also incorporated in a stepwise linear regression analysis to determine their correlation with the mechanical behavior of the vertebrae. Results. Several pQCT parameters correlated significantly with mechanical behavior. Of these, the trabecular area and the cortical/subcortical area had the strongest associations with the maximum load and stress magnitudes, respectively. The stepwise inclusion of additional predictors, while able to explain additional variance, did not significantly improve predictions of the response of the vertebral bodies to loading. Conclusion. pQCT parameters are quantitatively related to tissue mechanical behavior. The parameters often used in clinical evaluations were not found to be superior to some other pQCT parameters, and inferior to others. This suggests that the inclusion of additional morphologic parameters would improve estimates of the tissue mechanical tolerance over using densitometric parameters alone.