Purpose: Using the finite element analysis, the authors analyze the effect of the articulating material properties of the total hip arthroplasty to stress and micro-motion of the proximal femur and the femoral stem.

Material and methods: The head (28mm) and the acetabular component (outer diameter = 54mm, liner thickness = 11.4mm) were considered as ceramic on ceramic, cramic on polyethylene, metal on metal, metal on polyethylene and metal on metal-polyethylene. The femur was modeled with different friction coefficients according to the different contact portion of the femoral stem, which was modeled after Omni fit HA #9(Osteonics, Allendale, NJ). Non-linear contact analysis was proceeded in human with body weight 70Kg at one leg standing and stair climbing.

Result: The maximal yield strength was always higher in hard-hard coupling. In one leg standing, the site of maximal yield strength was represented at the contact point of articulation. In stair climbing, the site of maximal yield strength was represented at the same site in hand on hard coupling but at the lateral aspect of the neck in hard-soft couplings. There were no changes in the patterns of stress distribution but the micro-motions were up to the limit of bone in growth in hard-hard coouplings.

Conclusion: The maximal yield strength and the micro-motions revealed different values according to the articulating materials. These findings were considered valuable information to postoperative management and longavity of the total hip prosthesis but requiring the following experimental and clinical study.