Trajectory of Bearing Movement During Oxford Mobile-bearing Unicompartmental Knee Arthroplasty Using Kinematic Alignment Technique: a Retrospective Analysis

Abstract

Background: This study was performed to clarify whether the kinematic alignment technique can improve the trajectory of the bearing movement during Oxford mobile-bearing unicompartmental knee arthroplasty (Oxford MB UKA) compared with the traditional technique using a Microplasty instrument.Methods: We retrospectively analyzed patients who underwent UKA from January to June 2019. The kinematic alignment technique group (study group) comprised 23 patients (30 knees), and the Microplasty group (control group) comprised 25 patients (30 knees). The clinical outcomes, radiographic assessments, and intraoperative bearing movement trajectory and distance were compared between the two groups.Results: There were no differences in the baseline characteristics or clinical outcomes between the two groups (P > 0.05). There were also no differences in the postoperative femoral and tibial prosthesis varus and valgus angles, femoral prosthesis flexion and extension angles, tibial slope, or prosthesis convergence angle (P > 0.05). The contiguity between the femoral and tibial prosthesis in the study group was 4.8 ± 1.6 mm, while that in the control group was 6.3 ± 1.8 mm (P < 0.05). The difference in the bearing movement trajectory was significant, with an ideal trajectory in 23/30 cases in the study group and 14/30 cases in the control group (P < 0.05). The bearing movement distance showed no significant difference between the groups (P > 0.05).Conclusion: The prosthesis installation accuracy of the kinematic alignment technique in Oxford MB UKA was similar to that of conventional Microplasty instrumentation. However, the contiguity between the femoral and tibial prosthesis was smaller, and the bearing movement trajectory was more optimal.