Abstract
Aim: To find out when, at which interface, and to what extent migration of the Exeter stem after revision with morselized allograft bone and cement takes place and to evaluate if restricted weight bearing had any influence on the migration pattern. Methods: 40 stem revisions were followed by radiostereometry (RSA). The surgical procedure described by the Exeter group in England (Gie et al 1993) was used. Results: Most migration occurs within the first weeks after surgery. The Exeter stem migrates “within” the cement mantle and the stem-cement beam also migrates relative to femur.
All stems migrated distally and most of them also migrated medially or laterally and posteriorly. Migration was still observed in one third of stems between 1.5 and 2-year follow-ups. At 2 years stem subsidence averaged 2.5 mm, medial or lateral migration averaged 1.2 mm and posterior migration averaged 2.9 mm. No correlation to the preoperative bone stock deficiency was observed. Between 2 and 5 years only marginal migration occurred in 11 of the 15 stems followed for 5 years.
No differences in the migration pattern were detected when free weight bearing was allowed immediately after revision in hips without intraoperative skeletal complications as compared to when restricted weight bearing was practiced. No rerevision was performed. Conclusions: Most migration occurs early. Subsidence occurs of the stem within the cement mantle and of the stem-cement beam. Many stems migrate marginally even after 2 years but this does not deteriorate the results during the first five years. Restricted weight bearing postoperatively in uncomplicated cases might not be needed.
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.
