Summary

This study compares the clinical outcomes of restricted Kinematic Alignment (rKA) and conventional Mechanical Alignment (MA) methods in Total Knee Arthroplasty (TKA) using the ZimmerBiomet ROSA robotic system.

Abstract

Introduction

Our hospital adopts the Kinematic Alignment (KA) approach to recreate the joint surface before arthritic changes. We use the ZimmerBiomet ROSA robotic system to perform Total Knee Arthroplasty (TKA) following the KA method. This study compares the clinical outcomes of the restricted Kinematic Alignment (rKA) method with the conventional Mechanical Alignment (MA) method.

Methods

• Subjects: 27 varus knees (rKA: 18, MA: 12) that underwent unilateral TKA between July 2021 and were followed up for 1 year postoperatively.
• Procedure: Robotic-assisted unilateral TKA (ROSA knee system, Zimmer-Biomet)
• Implant: Vanguard®ID
• Evaluation: Hip-knee-ankle angle (HKA), lateral distal femoral angle (LDFA), medial proximal tibial angle (MPTA), condylar twist angle (CTA), patella tilting angle, joint line orientation angle (JLOA), range of motion (ROM), Timed Up & Go Test (TUG), Knee Injury and Osteoarthritis Outcome Score (KOOS), JOA score, Oxford Knee Score (OKS), and Forgotten Joint Score (FJS).
• Statistical analysis: JMP version 18, Chi-square test for categorical data, Wilcoxon rank-sum test for continuous data. Significance level: p<0.05.

Results

Radiographic evaluation showed significant differences in postoperative LDFA (rKA: 88.7±1.9°, MA: 89.6±0.7°, p=0.0281) and MPTA (rKA: 86.8±1.6°, MA: 89.3±1.3°, p=0.0014). While KOOS and OKS showed no significant differences, the JOA score at 1 year postoperatively was significantly higher in the rKA group (rKA: 82.5±9.4, MA: 75.6±7.6, p=0.0446). FJS showed significant differences at 6 months and 1 year postoperatively, with the 6-month scores being rKA: 65.6±6.4 and MA: 45.2±2.4.

Discussion

These findings suggest that rKA TKA may better restore the natural anatomical structure of the patient's knee, potentially contributing to improved functional outcomes. The higher Forgotten Joint Score (FJS) in the rKA group indicates that these patients may experience a more natural-feeling knee after surgery.

In conclusion, robot-assisted rKA TKA shows promising short-term results compared to MA, particularly in restoring natural knee anatomy and improving patient-reported outcomes. However, larger cohort studies with longer follow-up periods are needed to confirm these findings and assess the long-term impact of this alignment approach.