The Survivorship and Clinical Results of Minimally Invasive Unicompartmental Knee Arthroplasty at 10-Year Follow-up

Abstract

Background: In this study, we investigated the long-term clinical results and survival rate of minimally invasive unicompartmental knee arthroplasty (UKA) by collecting cases that had been implanted more than 10 years ago.

Methods: One hundred and twenty-eight patients (166 cases) who underwent Oxford phase 3 medial UKA using the minimally invasive surgery from January 2002 to December 2002 were selected. The mean age of the patients at the time of surgery was 61 years, and the duration of the follow-up was minimum 10 years. Clinical and radiographic assessments were performed using the Knee Society clinical rating system, and the survival analysis was done by the Kaplan-Meier method with 95% confidence interval (CI).

Results: The mean Knee Society knee and function scores improved significantly from 53.8 points (range, 25 to 70 points) and 56.1 points (range, 35 to 80 points) preoperatively to 85.4 points (range, 58 to 100 points) and 80.5 points (range, 50 to 100 points) at 10-year follow-up, respectively (p < 0.001). Failures following the UKA occurred in 16 cases (9.6%), and the mean time of the occurrence of the failure was 6.2 years after the surgery. The 10-year survival rate was 90.5% (95% CI, 85.9 to 95.0) when failure was defined as all the reoperations, whereas the 10-year survival rate was 93.4% (95% CI, 89.6 to 97.1) when the cases in which only revision total knee arthroplasty was defined as failure.

Conclusions: The results of this study show outstanding functions of the knee joint and satisfactory 10-year survival rate after minimally invasive UKA. Therefore, minimally invasive UKA could be a useful method in the treatment of osteoarthritis in one compartment of knee joint.

Keywords: Arthroplasty; Knee; Minimally invasive; Replacement; Survival rate.

Fig. 1. (A, B) Preoperative radiographs of a 75-year-old woman show osteoarthritis of the medial compartment in the left knee. (C, D) The last follow-up radiographs show findings at more than 10 years after minimally invasive Oxford phase 3 unicompartmental knee arthroplasty.

Fig. 2. Kaplan-Meier survivorship analysis curve showing 10-year survival rate of minimally invasive unicompartmental knee arthroplasty of 90.5% (95% confidence interval [CI], 85.9 to 95.0) with failure for any reason as the end point (group A) and 93.4% (95% CI, 89.6 to 97.1) with the revision of total knee arthroplasty as the end point (group B).