Bone remodelling adjacent to intramedullary stems: an optimal structures approach

The internal parameters in bone remodelling theories often are not clearly related to the bony structure which results from the simulations in which they are implemented. For a restricted class of bone remodelling theories, we have previously found a connection between overall structural optimization and the parameters within a continuum-level remodelling rule. In this study, we assess whether a simplified analytical formula based on structural optimization can predict the behaviour of a large-scale finite element bone remodelling simulation. The analytical formula predicts when bone will remain around an intramedullary implant. The predictions of the formula are borne out in the numerical results. This leads to a physical interpretation of one of the two parameters in the remodelling rule used. The results also show some characteristics which are clinically relevant. This study extends earlier results due to Huiskes for internal remodelling around intramedullary implants by using a different, numerically stable remodelling algorithm based on optimization. The study also shows a direct practical application of the optimizing remodelling theory the authors have developed previously.