High Survival Rate and Very Low Wear of Lateral Unicompartmental Arthroplasty at Long Term: A Case Series of 54 Cases at a Mean Follow-Up of 17 Years

Abstract

Background: Survivorship of lateral unicompartmental knee arthroplasty (UKA) has progressively improved. However, there are few studies describing long-term results, and no study reports on polyethylene (PE) wear in lateral unicompartmental arthroplasty. The aims of this study are to determine the survival rate of lateral UKA with a fixed, all-PE bearing, and the PE wear of the tibial implant at a minimum of 15 years follow-up.

Methods: From January 1988 to October 2003, we performed 54 lateral UKAs in 52 patients. All patients had isolated lateral osteoarthritis (OA). The mean age at the index procedure was 65.4 ± 11 years. Thirty-nine UKAs were available for follow-up (30 alive and 9 dead after 15 years). Twelve patients had died before 15 years and 3 patients were lost to follow-up. The mean follow-up was 17.9 years (range, 15-23 years).

Results: At the final follow-up, 8 knees of 39 (20.5%) had a surgical revision. The cumulative survival rate was 82.1% at 15 years and 79.4% at 20 years. The main reason of revision was progression of OA (87.5%), followed by aseptic loosening of the tibial component (12.5%). With a mean follow-up of 17.9 years, the mean PE wear was 0.061 mm/y. There was no radiographic loosening in the surviving implants and no revisions for wear. The mean functional International Knee Society score was 66.5 ± 26.8, with a mean objective score of 84.4 points ± 13.2. In the population without revision, 90.5% were satisfied or very satisfied at the latest follow-up.

Conclusion: Lateral UKA with a fixed, all-PE tibial bearing and a femoral resurfacing implant presents a high survivorship at long term, with very low PE wear.

Keywords: all-polyethylene; lateral unicompartmental knee arthroplasty; long-term follow-up; revision; wear.