Soft Tissue Releases Affect the Femoral Component Rotation Necessary to Create a Balanced Flexion Gap During Total Knee Arthroplasty

The structures that were released to balance the extension gap were recorded during 1500 consecutive TKA procedures, and the amount of femoral component external rotation (ER) necessary to balance the flexion gap was measured with a tensiometer. The amount of ER necessary to balance the flexion gap significantly decreased as more medial structures were released (1 structure = 4.7°, 2 = 4.1°, 3 = 2.8°, 4 or more = 1.1°, P < 0.012), whereas significantly greater ER was necessary when three or more lateral structures were released (1 structure = 5.3°, 2 = 5.5°, 3 or more = 8.6°, P < 0.03). Soft tissue releases affected the amount of femoral component ER necessary to balance the flexion gap, bringing into question the ability of techniques utilizing bony landmarks to properly align the femoral component in rotation.