Influence of tibial component slope on short-term clinical outcome for Oxford unicompartmental knee arthroplasty

Abstract

Objective: To investigate the effects of tibial component slope change after microplasty (MP) Oxford unicompartmental knee arthroplasty (UKA) on short-term clinical outcome. Methods: A total of 116 patients(128 UKAs)underwent UKA in Department of Orthopaedic Surgery of China-Japan Friendship Hospital between January 2014 and December 2015 were retrospectively reviewed. Totally 100 patients (108 UKAs) were finally included in the study. There were 31 males and 69 females, aging from 47 to 90 years (mean 67.2 years). The mean height was (161.9±8.4) cm and the mean body mass index (BMI) was (26.2±3.3) kg/m(2). The posterior tibial slope (PTS) at preoperative and postoperative were measured on the lateral radiograph. The postoperative PTS were divided into five groups (<3°, 3° to 5°, 5° to 7°, 7° to 9° and>9°). The Oxford Knee Score (OKS) was recorded. Pearson correlation analysis, ANOVA and t test were used to analyze data. Results: All operations were successfully accomplished and there were no transfusion, infection, thrombus and other complications. There was 1 patient accepted revision because of bearing dislocation. Compared to preoperative, the PTS decreased (6.5°±2.2° vs.9.6°±3.4°) postoperative, there was statistical difference (t=9.053, P<0.01). Only 3 patients were beyond the recommended range (2° to 12°). A total of 82 patients (86 UKAs) were followed up. The follow-up time was 1 to 2.9 years (mean 2 years). The OKS was 43.0±4.1 (mean 31 to 48). The PTS increased in 12 patients (12 UKAs) postoperative, the mean OKS was 40.5±5.2. The PTS decreased in 70 patients (74 UKAs), the mean OKS was 43.4±3.8. There were significant difference in OKS (t=2.347, P=0.021). There were no significant difference in OKS between the five groups. There were positive correlation between postoperative PTS and preoperative PTS (r=0.201, 95%CI: 0.001 to 0.396, P=0.037), there were no correlations between postoperative PTS and hight and BMI. There were negative correlations between OKS and postoperative PTS (r=-0.255, 95%CI: -0.063 to -0.427, P=0.018) and PTS change (r=-0.292, 95%CI: -0.08 to -0.475, P<0.01). Conclusions: Satisfying PTS can be obtained by use of Oxford MP instrumentation. The clinical outcome of the postoperative PTS decreased was relatively better. Too large posterior slope of the tibial implant should be avoided.