Variable Axial Rotation is Needed to Achieve a Balanced Flexion Gap in Total Knee Arthroplasty

Area of Science:

• Orthopaedic Surgery
• Biomechanical Engineering
• Medical Imaging

Background:

• Total knee replacement (TKR) aims to restore function and alleviate pain.
• Femoral component rotation is crucial for balanced knee kinematics and flexion gap stability.
• Current techniques often rely on predetermined rotational alignment, potentially leading to imbalances.

Purpose of the Study:

• To quantify femoral rotation in the axial plane for posterior-stabilized TKR using a modified gap-balancing technique.
• To investigate the influence of preoperative coronal alignment on femoral component rotation.
• To assess the variability of femoral axial rotation across different knee alignment groups.

Main Methods:

• Analysis of 2442 posterior-stabilized TKR cases from a computer-assisted orthopaedic surgery (CAOS) navigation system database.
• Stratification of knees into varus, neutral, and valgus groups based on preoperative coronal alignment.
• Recording of distal femoral and tibial resection angles and femoral component rotational position via CAOS navigation.

Main Results:

• Substantial variation in femoral axial rotation was observed across all alignment groups.
• The overall mean femoral rotation was 2.4° external.
• Mean rotation was 2.5° external for varus, 2.5° external for neutral, and 1.1° external for valgus knees (p < 0.0001).

Conclusions:

• A predetermined femoral component rotation may increase flexion gap asymmetry compared to intraoperative adjustment.
• Statistically significant differences exist in mean femoral component rotation between varus and valgus knees.
• Optimizing femoral rotation intraoperatively is essential for achieving a balanced flexion gap in TKR.