Improved Functional Outcomes With No Failures Three Years After Calipered Restricted Kinematic Alignment Total Knee Arthroplasty in Japanese Patients.

Aims Restricted kinematic alignment (rKA) has emerged as a safer alternative for total knee arthroplasty (TKA) in cases with extreme anatomical variations, particularly in Asian populations. However, it typically requires computer-assisted robotics and navigation. This study therefore evaluates the efficacy and safety of caliper-based rKA-TKA in a Japanese cohort without computer assistance. Methods We conducted a retrospective review of 67 knees in 43 patients who underwent caliper-based rKA-TKA between May 2020 and May 2021 at our hospital. Clinical outcomes were evaluated at a three-year follow-up, including Tegner activity score, Oxford knee score, Knee Society knee score and functional score, and Forgotten Joint Score 12. Radiological parameters were also assessed, such as mechanical hip-knee-ankle angle and coronal plane alignment of the knee classification. Results Significant improvements in clinical scores were observed at three years (p<0.001). Radiologically, 70% of knees were within the safe alignment range postoperatively (p<0.001). Notably, no revisions were required, and implant survival was 100%. Positive correlations were found between changes in mechanical hip-knee-ankle angle and improvements in Tegner activity score, Oxford knee score, and Knee Society knee score. Conclusion Caliper-based rKA-TKA achieved satisfactory alignment and clinical outcomes without computer assistance, demonstrating its safety and effectiveness for Japanese patients. Long-term follow-up is nonetheless warranted to confirm these findings.