Influence of cement stiffness and bone morphology on the compressive properties of bone-cement composites in simulated vertebroplasty.

Vertebroplasty is widely used to treat vertebral compression fractures. Little is known about the influence of morphological parameters of the bone on the properties of the bone-cement composite. Furthermore, although generic finite element (FE) models have been suggested as a way to compute the values of these properties, their accuracy has not been established. In the experimental part of this study, we tested bovine cancellous bone and three different polymethylmethacrylate bone cements and determined six quasi-static uniaxial compressive properties of bone-cement composite specimens and 10 morphological parameters of the bone. For the FE work, we used two simulations, one being μFE and the other unit cell FE. In conclusion, we found that (1) for composite specimens, that relative contribution of the cement to the overall response of the composite increases with increasing cement stiffness; (2) the anisotropy ratio is the bone morphological property that exerts the most significant influence on the experimentally obtained compressive properties of the bone-cement composites determined; (3) the accuracy of the computed compressive properties of the composites ranged from low to high, depending on simulation method used. The largest errors, however, can partially be explained by difference in boundary conditions between the experimental testing and the simulation techniques. The lattermost finding points to the potential for simplified FE models being incorporated into automatic material mapping schemes in whole bone vertebra FE simulations.