Abstract
Introduction: Stress shielding has been found to cause cortical thinning and loss of trabecular bone in the proximal femur due to stiff steam and elastic bone. To avoid these problems a prosthesis was developed according to the concept of isoelasticity. Its aim was to ensure the implant and the bone to deform as one unit loading the bone in a more physiological way. Methods: From 1984 Ð1987 we performed 149 total hip replacements using third generation Mathys isoelastic polyacetal stem with stainless-steel heads and polyethylene cementless acetabular cups. Average patient age was 47 years (21–82). Eleven patients (12 hips) has died before revision and fourteen (15 hips) were lost to follow up. Results: Hitherto 69 hips were revised, þve due to infection. The 10 years revision rate for any reason was 68.7%. The remaining 48 patients (53 hips) have been clinically and radiologically assessed or reviewed by a questionnaire. In these patients the average HHS was 80 points. Thirteen among them had failed radiologically, many without a poor subjective result. Conclusions: The performance of this prosthesis was unacceptably poor but nevertheless the concept of isoelasticity should not be completely disregarded. Future trends may reconsider and reintroduce some new materials or implant designs which would be able to achieve the aim of isoelasticity without former problems. Long term total hip loosenings are still all but solved.
Theses abstracts were prepared by Professor Dr. Frantz Langlais. Correspondence should be addressed to him at EFORT Central Office, Freihofstrasse 22, CH-8700 Küsnacht, Switzerland.
