Abstract
The long term survival of well-cemented, polished tapered stems is now proven. In spite of this, doubts remain about the phenomenon of subsidence which is essential to the mechanical integrity of these devices yet anathema to those surgeons who favour collared stems. Believing that the quality of cementing is more important than stem geometry, this study looked at the subsidence of 880 polished tapered stems [Corin, Taperfit} all implanted through an antero-lateral approach with a consistent cementing technique. In addition, for this implant, a new stem introducer was used to ensure accurate placement within the cement mantle.
Four sizes of stem were available and were used in the following numbers: size 1 [345], size 2 [381], size 3 [117] and size 4 [37]. Most subsidence occurs in the first year after surgery. These patients were all assessed with a minimum of one year. There was no difference in the rates of subsidence between these stem sizes. There were 14 revisions. Ten were for aseptic cup loosening and 4 for infection. There were no stem failures due to loosening.
Although all manufacturers producing such stems market a variety of sizes none emphasise that the stem geometry varies considerably from the smallest to the largest. Indeed, the variation within individual ranges is greater than the variation between sizes from different manufacturers.
The results obtained strongly support the thesis that it is the interaction between the cement and the stem which is important and that with a tapered polished stem the quality of cement technique is the least forgiving part of the operation
Correspondence should be addressed to Mr John Hodgkinson, BHS, c/o BOA, The Royal College of Surgeons, 35–43 Lincoln’s Inn Fields, London WC2A 3PE.
