The effect of femoral prosthesis design on cement strain in cemented total hip arthroplasty.

Finite element studies show that the highest cement stresses are located at the most proximal and distal ends of the prosthesis. In vitro biomechanical and histologic analyses of autopsy-retrieved cemented femoral components show these areas to be associated with cement-prosthesis debonding. In this study, cement strains were measured in 2 geometrically different femoral stems in paired cadaver femora: A straight, collared, moderately tapered stem (Centralign) was compared with an anatomically curved, collarless, dramatically tapered stem (Scientific Hip Prosthesis [SHP]). Results showed that the maximum strain and the overall strain profile differed between the 2 stems. The Centralign had peak strains located at the most proximal gauge positions, whereas the peak strains of the SHP were located around the middle of the femoral stem. Minimization of cement strain, especially at the crucial proximal and distal areas of the stem, by altering component design may be able to reduce cement-prosthesis debonding and improve clinical results.