Stem fracture with the Exeter prosthesis. 3 of 27 hips followed for 10 years.

Abstract

We report the results of a 9-11-year clinical and radiographic follow-up of 27 Exeter prostheses in which cement pressurizing technique was employed. 3 stems fractured and 3 other stems and 1 cup underwent aseptic loosening. The remaining prostheses had satisfactory clinical and radiographic results. Stem subsidence was seen only as part of a loosening process. We suspect that the pronounced taper design is responsible for the poor results. While the slender and weak distal end is fixed in a thick cement mantle, the wide proximal part allows only a thin cement layer, easily subjected to mechanical disintegration. Proximal debonding increases both the stress on the distal part of the stem and the distal bone-cement interface shear stress. Hence, we believe that the same process underlies both the loosenings and the stem fractures. The presently employed Exeter stem is manufactured from the stronger Orthinox steel, which may diminish the risk for fracture, but it has retained the extreme taper design. It is not likely that a polished surface or improved cementing will prevent stem fracture. Therefore, one should still be concerned about late fractures of the Exeter stem.