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Functional Alignment Achieved a More Balanced Knee After Robotic Arm-Assisted Total Knee Arthroplasty than Modified
Hong-Yeol Yang1, Jong-Keun Seon1, Ji-Hyeon Yim2
1Department of Orthopaedic Surgery, Chonnam National University Medical School and Hospital, 322, Seoyang-ro, Hwasun, Chonnam 58128, Republic of Korea.
Journal of Clinical Medicine
|February 13, 2025
Summary
Functional alignment (FA) significantly improved knee balance after total knee arthroplasty (TKA) compared to modified kinematic alignment (KA). This robotic-assisted technique enhances joint stability and patient outcomes post-surgery.
Area of Science:
- Orthopedic Surgery
- Biomechanical Engineering
- Robotic Surgery
Background:
- Total knee arthroplasty (TKA) aims to restore knee function.
- Achieving optimal ligament balance in extension and flexion is crucial for TKA success.
- Kinematic alignment (KA) and functional alignment (FA) are surgical planning principles for TKA.
Purpose of the Study:
- To compare the ligament balance achieved with a modified kinematic alignment (KA) plan versus functional alignment (FA) after TKA.
- To evaluate the impact of FA adjustments on component positioning and joint balance.
- To assess the clinical outcomes associated with each alignment strategy.
Main Methods:
- Retrospective cohort study of 100 TKA patients using an image-based robotic system.
- Ligament balance in medial and lateral compartments assessed in extension and 90° flexion.
- Component positioning adjusted based on FA principles to achieve balance (≤2 mm difference).
- Comparison of implant positioning and balance between modified KA and FA groups.
Main Results:
- FA demonstrated significantly superior balance in extension (99.0% vs. 86.0%) and flexion (98.0% vs. 43.0%) compared to modified KA.
- Mean gap balance differences were significantly smaller with FA (0.1 mm extension, 0.1 mm flexion) versus modified KA (0.6 mm extension, 2.3 mm flexion).
- FA resulted in more external rotation of the femoral component (2.5° vs. 0.0°) relative to the transepicondylar axis.
- Significant improvements in patient-reported outcome measures were observed at two years post-TKA for FA.
Conclusions:
- Functional alignment (FA) provides superior knee joint balance in both extension and flexion following TKA compared to modified kinematic alignment (KA).
- FA achieves this balance without compromising the soft tissue envelope.
- The improved joint balance with FA correlates with significant enhancements in clinical outcomes at the two-year follow-up.
