SIX-YEAR OUTCOME IN A CONSECUTIVE SERIES OF 122 UNICOMPARTMENTAL KNEE PROSTHESES

Abstract

Purpose of the study: The aim of this study was to report outcome after more than six years follow-up of a series of 122 unicompartmental prostheses.

Material and methods: Cemented HLS® unicompart-mental surface-coated prostheses were implanted in 111 patients (122 knees, 88% medial and 12% lateral) between January 1995 and November 1997 by the same surgeon. These knees presented unicompartmen-tal osteoarthritis (91%) or unicondylar necrosis (9%). An independent senior surgeon reviewed 94 prostheses. Seventeen patients died and ten institutionalized patients free of complaints about their knee could not be fully assessed. Only three patients (2.7%) were lost to follow-up). Clinical data were assessed with the IKS criteria. A complete radiological work-up was available to compare preoperative images with the last follow-up results. Mean follow-up was 88 months (range 72–108 months).

Results: After the implantation, 96% of patients were satisfied or very satisfied; 84% had no or little pain. Mean flexion was 133° (range 90–150°). The mean knee score at follow-up was 86/100 (40/100 preoperatively), mean function score 77/100 (61/100 preoperatively). Mean residual misalignment was 6° (7° varus for medial prostheses and 4° valgus for lateral prostheses). Tibial or femoral lucent lines were observed for 22% of the prostheses but with no change and no clinical expression. There was one case of tibial polyethylene wear (1mm). There were eight failures (all before 24 months) with revision with a total knee arthroplasty (two infections, one overlarge component, two tibial loosenings, 3 unexplained pain). The Kaplan-Meier survival at maximum follow-up of 108 months was 93.67%.

Discussion: The prostheses implanted in this series were correct indications according to the preceding symposiums. We analyzed the clinical and radiological outcome (overall axial correction, tibial and femoral correction), failures, and reasons for incomplete results.

Conclusion: Outcome at more than six years in this series of resurfaced knee prostheses with a polyethylene plateau was good, supporting the correct choice of implant and technique. These results also enabled validation of the principle that unicompartmental arthroplasty is a valid alternative for the treatment of unicompartmental osteoarthritis of the knee joint. Analysis of the failures and the incomplete results discloses interesting avenues for optimizing the surgical technique and improving future clinical and radiological results.