Stress shielding and bone resorption in THA: clinical versus computer-simulation studies.

"Stress shielding" of bone around noncemented prosthetic hip stems causes long-term adaptive bone resorption which threatens the integrity of the fixation. Recently, computer-simulation models based on adaptive bone-remodeling theory in combination with finite-element methods have been developed. These models can be used to predict the extent of long-term resorption. In this paper a comparison is presented between the results of these predictions and those of precise measurements in retrieval hip-replacement specimens reported by Engh and associates (1992). It is shown that certainly the predictions and the actual clinical findings are subject to the same trends. Under certain assumptions, these results even match precisely. It is also shown that both clinical results and simulation predictions can be approximated by a simple formula, in which the amount of bone loss is related to the ratio between stem stiffness and preoperative bone density.