150. LONG-TERM OUTCOMES IN 43 UNICOMPARTMENTAL OXFORD PROSTHESES FOR VARUS DEVIATION OF THE KNEE

Abstract

Purpose of the study: The purpose of this work was to analyse the long-term results obtained with 43 medial Oxford unicompartmental prostheses implanted from 1988 to 1994 for varus deviation of the knee.

Material and methods: Initially, the series included 56 patients (59 prostheses), but data were incomplete for nine patients who had died and five who were lost to follow-up. The analysis thus included 40 patients (74%): 16 were living at the time of this review (40%), 14 had died (35%) and ten had a total knee arthroplasty after failure of the Oxford prosthesis (25%). Mean age at initial surgery was 68.83±7.54 years (range 47–86). There were 13 surgical revisions: four for loosening, three for deterioration of the lateral compartment of the knee, two for repeated meniscal dislocation, two for rupture of the femoral implant and one repeated revision for impingement between the meniscal element and the femoral condyle. For ten knees, we replaced the implant with a total knee arthroplasty and in three others, we changed the meniscal piece.

Results: One year after the initial operation, the overall IKS score was 189.67±14.43 points (115–200), i.e. 93% good and very good outcomes. Regarding the initial radiographic results, overall varus of the lower limb had improved from 171.31±0.46 (161–180) preoperatively to 178±3.21 (170–186) postoperatively. Sixty-three percent of the patients had normal alignment or slight undercorrection (0–4), 19% had a greater undercorrection (5–9), 2% an excessive undercorrection (10), and 16% an over correction (181–186). At review, mean follow-up was 14.8±1.16 years (13–17) and mean patient age was 82 years (n=16). The mean overall IKS was 145.52±39.90 points. Sixty-nine percent of the patients were satisfied or very satisfied with the prosthesis. The prosthesis survival was 93% at one year, 90.5% at five years, 74.7% at ten years and 70.1% at fifteen years.

Discussion: Globally, the unicompartmental Oxford prosthesis has not provided in our hands the results we expected. Certain failures could undoubtedly have been avoided and should be included in the learning curve. Nevertheless, this prosthesis is certainly difficult to insert and carries a non-negligible risk of undercorrection, especially when the deviation is overcorrectible and care is taken to avoid dislocation of the meniscal element.