Micro-FE analyses of bone: state of the art.

The ability to provide a complete characterization of elastic properties of bone has vastly improved our understanding of trabecular bone mechanical properties. Based on this information, it was possible to validate several mechanical concepts related to the elastic behavior of trabecular bone that could not be validated earlier. With recently developed micro-CT scanners and the availability of large parallel computer systems, this technique has also enabled the determination of physiological bone tissue loading conditions from very large microFE models that can represent whole human bones in detail. Such analyses can provide the data needed for a better understanding of bone failure processes or cell mediated load adaptive remodeling processes. Computational demands for whole bone analyses, however, are still excessive. Unlike linear stress and strain analyses, the application of PFE to study non-linear processes, in particular bone failure mechanisms, is still in an early phase Results of recent studies, however, are promising and indicate that an accurate prediction of bone failure with these techniques is possible. Compelling features of such analyses are that they enable multi-axial failure criteria at the apparent level to be developed using primarily computational methods as well as that they can provide a basis for detailed analysis of micro-mechanics associated with trabecular failure at the apparent level. The application of microFE techniques to analyze bone in vivo is in an early stage as well. First results have indicated that, although the resolution of presently available in vivo imaging techniques (i.e. pQCT and MR) is much less than that of images used so far for uFE analyses, the technique can provide meaningful elastic properties of trabecular bone in vivo in most cases. It is expected that the remaining uncertainties in the microFE results can be eliminated as soon as the resolution of in vivo images is improved. With the fast developments in pQCT(47) and MR scanning, this will probably be in the near future.