Abstract
Finite element stress analysis is frequently used to evaluate wear propensity in total joint replacement components. Previous work has primarily concentrated on static UHMWPE material properties and has not included important time-dependency. In this study, a viscoelastic material model was used to evaluate tibio-femoral contact stresses during simulated in vivo loading conditions of combined compressive load and femoral rotation and translation. After initial loading and displacement, the UHMWPE tibial component showed significant creep displacement and stress relaxation with constant load. These results demonstrate the importance of including time-dependent material behavior in assessing contact stresses in finite element analyses or experimental evaluation of TKR designs. The material recovery after initial indentation is slow enough to allow continued femoral articulation over newly created ridges on the edge of contact, and this effect may play a role in tibial component wear and damage.
