Fixed-bearing unicompartmental knee arthroplasty tolerates higher variance in tibial implant rotation than mobile-bearing designs.

Abstract

UKA necessitates a learning period. From this point of view, it would be logical to prefer the design that tolerates suboptimal tibial rotations better, especially for inexperienced surgeons. The aim of this study was to evaluate and compare the clinical and radiological results of mobile-bearing and fix-bearing UKA designs in case of suboptimal tibial rotations. A retrospective case-control evaluation was made of all the patients with medial compartment osteoarthritis, treated between January 2011 and January 2015. 324 patients ideal femoral rotation were enrolled in the study. 153 patients (Group 1) were treated with fix-bearing design with a mean 28.8 ± 11.3 month follow-up and 171 patients (Group 2) were treated with mobile-bearing design with a 31 ± 14.3 month follow-up. Each patient in groups was subdivided into (A): optimal tibial rotation, (B): external rotation of tibial component > 5°, (C): internal rotation of tibial component > 5° subgroups. WOMAC and KSS scores of each patient at preoperative and postoperative final control were compared between groups and subgroups. No significant differences were determined between the groups in terms of mean follow-up time (p = 0.0612), preoperative WOMAC, and KSS scores (p = 0.754 and p = 0.832, respectively). No significant differences were determined between subgroups 1A and 2A in terms of WOMAC and KSS scores at the final evaluation (p = 0.314 and p = 0.546, respectively). A significant difference was determined between subgroups 1B and 2B in terms of WOMAC and KSS scores (p = 0.021 and p = 0.012, respectively). In addition, the difference between subgroups 1C and 2C was significant (p = 0.047 and p = 0.034, respectively) at the final evaluation. Both mobile- and fix-bearing designs are beneficial in the treatment of medial compartment osteoarthritis of the knee. However, in case of both tibial internal or external suboptimal tibial rotations, fix-bearing design have better results compared to mobile-bearing design. Level III retrospective comparative clinical study.