The influence of design parameters on calcar stresses following femoral head arthroplasty.

A two-dimensional finite element model (FEM) was used to investigate the effect of various prosthesis design parameters on stresses along the proximal medial aspect of the femur. Strain calculations were compared to reported experimentally measured strains for an intact femur and femur containing a prosthesis in an effort to verify the FEM results. The results of the study indicated that stress levels in the medial aspect of the femur approaching those of the intact femur are possible with a device having an elastic modulus similar to bone. It was found that acrylic bone cement had little effect on stress profiles in the medial aspect when compared to stresses for devices utilizing a direct bone to implant attachment mechanism. It was also found that reduction in implant stem length and elastic modulus of tissue present at the prosthesis--bone interface could be used to increase stresses in the medial aspect; however, their effects were not as dramatic as reducing the elastic modulus of the stem material.