Three dimensional stress analysis of the femoral stem of a total hip prosthesis.

Abstract Stress distributions in an implanted femoral stem were investigated using a three dimensional finite element model of the implanted stem, surrounding bone and cement. The model was constructed for evaluation of stem stress. Experimental studies were used to validate the stem stress predictions. Three orthogonal loads were applied to the ball of the stem directed inferiorly, laterally and posteriorly. The resulting stress distributions indicate that the inferiorly directed load is responsible for most clinically observed failures. However, the stresses that result from the lateral and posterior loads were found to be high enough to endanger the survival of these devices. The shear stress at the stem cement interface was found to resist stem subsidence or pull out, but was not a factor in supporting the bending moment.