[Stresses on the femur following hip joint replacement]

The stresses in femur after joint replacement have been calculated with the finite element method and the results were checked by using strain gauges glued on the surface of the femur and on the prosthetic stem. The influence of stem length and prosthetic collar on the distribution of the stresses have been investigated. The stem length has only a minor effect on the stress distribution if the stem has a texture which allows transfer of tension and shear at the interface endoprosthesis--bone cement. Merely at the tip of the stem changes of the stresses are obvious. The stresses in the bone near the resection plane are distinctly reduced if the prosthesis has a collar. These results have very limited relevance for implants with a smooth stem which does not allow the transfer of tension and shear at the interface endoprosthesis--bone cement.