Comparison of patient satisfaction and function outcomes between restricted kinematic alignment and mechanical alignment: An early follow-up study

Background Mechanical alignment (MA) is the gold standard for total knee arthroplasty (TKA). However, MA will inevitably modify the patient's native knee anatomy. Another alignment option is kinematic alignment (KA), which aims to restore the original anatomy of the knee. In recent years, restricted kinematic alignment (rKA), which aims to restore native knee kinematics without reproducing the extreme knee phenotype, has been developed as an alternative to unrestricted KA. This study was designed to evaluate the clinical outcomes and satisfaction scores between patients who underwent rKA and those who underwent MA during TKA. Methods We retrospectively analyzed the clinical data of 45 patients who were diagnosed with osteoarthritis and underwent MA-TKA and 45 patients who underwent rKA-TKA from January 2022 to January 2023. Demographic, perioperative, and radiological data were collected and compared. Unpaired two-sample t tests for continuous variables and χ ² tests for categorical variables were used to compare various measurements between two groups. The patient-reported outcome measures at baseline(T0) and at 3 (T3), 6 (T6), and 12 (T12) months after surgery were recorded and statistically analyzed. Result Forty-five robotic-assisted rKA-TKAs were performed, and 45 conventional MA-TKAs were performed. The changes in the hospital for special surgery score (HSS), visual analogue scale (VAS), forgotten joint score (FJS-12), knee society score (KSS), patient satisfaction, and complications from T0 to T12 for patients who underwent rKA were equal to those who underwent MA (86.58 vs. 86.22, P > 0.05 (KSS-Clinical, T12), 73.40 vs. 75.00, P > 0.05 (KSS-Function, T12), 86.11 vs. 85.28, P > 0.05 (HSS, T12), 0.87 vs. 0.82, P > 0.05 (VAS, T12), 83.29 vs. 83.38, P > 0.05 (FJS-12, T12), and 4.57 vs. 4.43, P > 0.05 (Satisfaction, T12)). The net change in the hip-knee-ankle (HKA) and medial proximal tibial angle (MPTA) for the constitutional varus was greater (P < 0.05) than that for the constitutional valgus knee in the rKA group. Both groups have a good range of motion (ROM). No revision was performed in the two groups at the one-year follow-up. Conclusion rKA is safe for short-term TKA and is a valid alternative to MA.