Abstract
Purpose: The Oxford unicompartmental prosthesis has congruent joint surfaces due to use of a mobile meniscus whose upper part matches the sphere constituted by the femoral component. The purpose of this work was to report results in a series of 75 prostheses studied with mean follow-up of 12.4 years (range 10–14 years).
Material and methods: Mean age of patients was 65 years (38–84), with 67% women and mean body mass index of 28.7 (21.2–40.6). Patients gave their subjective assessment of the arthroplasty and the IKS scores were determined. Radiographically, the mechanical alignment of the lower limb was evaluated pre- and postoperatively on the full stance images. The Kennedy classification (4 grades) was used to assess passage of the mechanical axis through the knee.
Results: At last follow-up, three patients were lost and eight had died. According to their subjective assessment, 84% of the patients were enthusiastic or satisfied. The overall IKS score showed that 52% of the patients were above 180 points, 25% above 150 points. Mean varus was 11° (2–24°) preoperatively and 5.7° (5° valgus to 14° varus) at last follow-up. The mechanical axis passed in the sufficient correction zone (c or 2) in 77% of the knees, undercorrection zone in 17% and in the overcorrection zone in 6%.Seven prostheses were revised for mechanical failure: four for loosening, two for extensive degeneration, and one for pain giving a survival curve of 90% at 12 years. It must be added that two meniscal dislocations occurred, one early due to wound dehiscence and infection and one late, both after a fall.
Discussion: Most loosenings occurred early and at the tibial level. Defective alignment could be incriminated in one case. The other knees exhibited a reactive line under the tibial plateau. The rate of dislocation should probably decline with the use of progressive reamers, not available at the time of this series. Finally none of the prostheses were revised for wear, confirming the proper prosthesis design.
The abstracts were prepared by Docteur Jean Barthas. Correspondence should be addressed to him at Secrétariat de la Société S.O.F.C.O.T., 56 rue Boissonade, 75014 Paris.
