The Medial Pivot design achieves better sagittal plane balance in the restricted kinematic alignment total knee arthroplasty

Introduction: Achieving sagittal plane balance is important to total knee arthroplasty (TKA) for providing mid-flexion stability and potentially increasing patient’s satisfaction. This study aimed to compare the sagittal plane parameters, range of motion (ROM), and patient-reported outcomes (PROMs) between patients received the cruciate retaining (CR) and the patients received medial-pivot (MP) in the restricted kinematic alignment TKA. Methods This retrospective study including a total of 124 patients who underwent TKA in Department of Orthopedics of Peking Union Medical College Hospital between February 2024 and January 2025. Patients were assessed preoperatively and 12 months postoperatively. All patients taken X-ray imaging in pre-operation and on the third day after the operation. Clinical assessments including the Forgotten Joint Score (FJS), physical examination including the assessment of the active ROM of the knee. The HKA (Hip-Knee-Angle), LDFA (Lateral Distal Femoral Angle), MPTA (Medial Proximal Tibial Angle), LFCA (Lateral Femoral Component Angle), LTCA (Lateral Tibial Component Angle), patella thickness, patella length, posterior femoral condylar offset (PCO), Coronal femoral width (LFW), PCO ratio, and posterior tibial slope (PTS) were taken from the X-ray imaging. Results There were 60 patients in the MP-TKA group and 64 patients in the CR-TKA group. Pre-operatively, there were no significant differences between the two groups in terms of demographic data, HKA, LDFA, MPTA, sagittal plane parameters, and FJS (p > 0.05). The MP group was more advantageous in changes of PCO (MP group changes of PCO: 2.42 ± 1.52 mm vs CR group changes of PCO: 3.62 ± 2.11 mm p < 0.001), the post-operation PCO and PCO ratio was significantly less in the MP group (MP group PCO: 26.11 ± 4.08mm vs CR group PCO: 27.65 ± 3.36mm p = 0.024; MP group PCO ratio: 0.45 ± 0.06 vs CR group PCO ratio: 0.48 ± 0.05 p = 0.001), there were no significant differences between the two groups in terms of the post-operation HKA, LDFA, MPTA and others sagittal plane parameters (p > 0.05). The post-operative ROM was significantly better in the MP group in 3-days post-operation and the 12-months post-operation (3-days post-operation in MP group:102.92°±7.93 vs 3-days post-operation in CR group:97.34°±5.49 p < 0.001, 12-months post-operation in MP group:103.35 ± 6.10 vs 12-months post-operation in CR group: 100.52 ± 4.97 p = 0.024) . Conclusion The MP design achieves better sagittal plane balance compared with the CR design TKA.