A 3D multilayered model to simulate sterilized knee prostheses under walking conditions : analysis of gamma irradiation effects in UHMWPE
Résumé
Ultra High Molecular Weight PolyEthylene (UHMWPE) is the polymer bearing material most commonly used for the design of the tibial insert in total knee joint replacement (TKJR). Sterilization by gamma irradiation in air causes oxidative changes in the polymer component that leads to mechanical property variations through its thickness. This may be one of the causes of the component failure. A general three‐dimensional elastic contact model has been therefore developed to predict both the contact stresses and the resulting internal stresses accounting for the plastic component finite thickness and its multilayered structure (constitutive layers of different thickness and mechanical properties) resulting from oxidation. Predictions of the maximum contact pressure and internal stresses have demonstrated that sterilization induces higher contact pressure, stress discontinuities at layer interfaces, possible bending effects and delamination risks.