Finite element-based preclinical testing of cemented total hip implants

Abstract

We developed a finite element model to preclinically test cemented hip implants for damage accumulation, including cement crack formation, creep, and stem migration. Using this model, we simulated the mechanical failure processes of four cemented total hip arthroplasty implants (Lubinus SPII, Mueller Curved, Exeter and Charnley, all with known clinical results) during cyclic normal walking and stair-climbing loads. These four implants were selected to ascertain whether the simulation predicted greater damage development around clinically inferior stems, whether clinically inferior designs could be identified by an initial stress analysis without the prediction of cement damage, and whether the simulation could predict high implant subsidence rates in combination with minimal cement damage. Based on the predicted cement crack patterns and crack formation rates, the simulation correctly identified the clinically inferior implant designs. Based only on the initial stress analysis under a stair-climbing load, it was not possible to identify clinically inferior designs. High subsidence values and minimal cement damage were predicted for the Exeter implant, similar to clinical findings. Our findings suggest the simulation may be effective in differentiating between a range of implants and design features.