Effect of PCL on flexion-extension gaps and femoral component decision in TKA.

This study was done to evaluate the change of medial-lateral gap in flexion and extension after posterior cruciate ligament (PCL) release in severely deformed knees and to determine how PCL release affects bone resection, rotation, and size of the femoral component and polyethylene thickness in converting to a PCL-sacrificed design. Thirty primary osteoarthritis patients with severe varus deformity or flexion contracture were enrolled. After releasing the PCL, the medial gap in extension increased by 1.2 mm, the lateral gap in extension increased by 0.3 mm, the medial gap in flexion increased by 4.5 mm, and the lateral gap in flexion increased by 3.4 mm. Compared with PCL-retained prostheses, the mean external rotation of the femoral component decreased by 1.6 degrees in the PCL-sacrificed type. Polyethylene thickness increased by 1.2 mm. In 12 cases, a larger femoral component was needed. In 8 knees, the size of the femoral component and the thickness of polyethylene did not change; however, posterior femoral resection could be decreased. In 8 knees, thicker polyethylene was planned with slightly increased distal femoral resection. After PCL cutting, flexion gap increased significantly compared with extension gap; however, correction of varus deformity was not significant. Conversion to PCL-sacrificed design resulted in a decrease in external rotation of the femoral component and increased the size of the femoral component or the thickness of the polyethylene insert.