Increased Microstructural Variability Is Associated With Decreased Structural Strength but With Increased Measures of Structural Ductility in Human Vertebrae

The lack of accuracy in the prediction of vertebral fracture risk from average density measurements, all external factors being equal, may be because bone mineral density (BMD) is less than a perfect surrogate for bone strength but also because strength alone may not be sufficient to fully characterize the structural failure of a vertebra. Apart from bone quantity, organization of micro-architecture would have a role in governing mechanical properties of vertebrae. An earlier study indicated that within-vertebra variability, measured as the coefficient of variation (COV) of bone volume fraction (BV/TV) or as COV of finite element-estimated apparent modulus (E_FE) correlated well with vertebral strength [1]. Therefore, as an extension to our earlier study, we investigated i) whether the relationships of vertebral strength found with COV of BV/TV and COV of E_FE could be extended to the COV of other micro-structural parameters and microcomputed tomography-estimated bone mineral density (μCT-BMD) and ii) whether COV of microstructural parameters were associated with structural ductility measures.