Matched-pair analysis of clinical and radiological results of medial-pivot total knee arthroplasty versus posterior stabilized total knee arthroplasty

Abstract

Introduction: Total knee arthroplasty (TKA) with a medial-pivot design was developed to mimic the natural kinematics of the knee. Studies have shown satisfactory survivorships and medium-term outcomes. However, controversy remains as the clinical superiority when compared to posterior stabilized (PS) TKA has yet to be seen. The purpose of this study is to assess clinical outcomes of the medial-pivot knee compared to PS TKA. Methodology: Since 2015, 119 medial-pivot TKA were included and matched to 119 PS TKA based on age, gender, body mass index and pre-operative alignment. Baseline characteristics were compared. Clinical outcomes measured included pre-operative and post-operative knee flexion deformity, range of motion, Knee Society Knee Score (KSKS) and Knee Society Function Score (KSFA). Radiographic evaluation with pre-operative and post-operative hip-knee-ankle mechanical alignment were also analysed. Matched-pair analysis was used to determine statistical significance. Results and Analysis: The average follow-up was 1 year. Baseline characteristics including age, gender, BMI, pre-operative range of motion, KSKS, KSFA, mechanical alignment and follow-up time were comparable (p>0.05). Range of motion fared worse in the medial-pivot TKA group. There were 4.5 degrees more flexion range gained in the PS TKA group compared to the medial-pivot group (p<0.01). However, post-operative clinical scores were significantly better in the medial-pivot TKA group with post-operative KSKS scores of 93.7 compared to 86.5 in PS TKA (p<0.01). Other clinical parameters including knee flexion deformity, KSFA scores and radiological alignment were otherwise similar. Discussion and Conclusion: Matched-pair analysis of medial-pivot knees showed better clinical outcome scores despite less range of motion gained.