The possibility of failure prediction in hip and knee prosthesis by using a damage estimator

ABSTRACT Finite element simulatios were performed to dynamically determinate the area of the contact, the contact pressure and the strain energy density (identified as a damage function) for three different activities ? normal walking, ascending stairs and, descending stairs ? that could be considered to define the level of the activity of the patient. The finite element model uses a modern contact mechanism that includes friction between the metallic femoral condyles or femoral head (considered rigid) and the tibial polyethylene insert or acetabular cup respectively, considering a non-linear behaviour). For all three activities, the finite element analyses were performed, and a damage score was computed. Finally, a cumulative damage score (that accounts for all three activities) was determined and the areas where the fatigue wear is likely to occur were identified. A closer look at the distribution of the damage score reveals that the maximum damage is likely to occur not at the contact surface, but in the subsurface.