Effects of stem design and material properties on stresses in hip endoprostheses.

With the aid of a three-dimensional finite element stress analysis a parameteric study of the essential aspects of the femoral component of hip endoprostheses was carried out. Various designs were investigated; these included the prosthetic stem length, the existence or non-existence of the prosthetic collar and the elastic modulus of stem and cement. Variations in the stem length have only minor effects on the stress distribution for a stem length greater than 100 mm, but the elastic modulus of the prosthetic stem has a considerable influence on the stresses. A high elastic modulus of the stem increases the stresses in the stem but it decreases stresses in the cement. The cement stresses increase with an increase in the modulus of elasticity of the cement.