Abstract
Background
When positioning and rotating the femoral cutting block (AP) on the femur it can either be done according to bony landmarks (measured resection) or by tensioning the flexion gap and positioning it parallel to the tibia (gap balanced technique.) Accurate rotation of the femoral component is essential to ensure a symmetric flexion gap to ensure optimal tibio-femoral kinematics and patello-femoral tracking.
Methods
74 consecutive total knee replacements were assessed intra-operatively for symmetry of the flexion gap by applying a varus and a valgus stress and digitally recording the opening with a computer assisted navigation system. External rotation of the femoral component according to the bony landmarks was measured radiologically. This was compared to the external rotation suggested by the navigation intra-operatively using a gap balanced workflow.
Results
The gap balanced technique gave a symmetric flexion gap with less than 3 mm side to side difference in 95% of cases. In 84% of cases (62 of 74) the gap balanced technique was more accurate than the measured resection technique in determining femoral rotation. In 16 % of cases (12 of 74) the same rotation was measured with the two techniques. In no case was the measurement more accurate with the measured resection technique. This result was highly statistically significant.
Conclusion
The gap balanced technique is more accurate than measured resection for determining axial rotation of the femoral component in total knee arthroplasty.
NO DISCLOSURES
