Effect of PCL on Flexion-Extension Gaps and Femoral Component Decision in TKA

Abstract

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.

Is the effect of a posterior cruciate ligament resection in total knee arthroplasty predictable?

“…These results are generally in line with the majority of existing studies [9,[16][17][18][19][20]. In this context, we investigated high flexion grades and found that the biggest joint-gap increase was between 110°and 140°.…”

“…If the gap-balanced procedure is used, PCL release leads to a constant reduction of the femoral component's external rotation. Similarly, Park et al measured a reduced external rotation of the femoral component of 1.6°after PCL resection [20].…”

“…In this context, we investigated high flexion grades and found that the biggest joint-gap increase was between 110°and 140°. To our knowledge, all other studies focused only on the joint gap between full extension and 90° [9,12,13,[16][17][18][19][20][21]. The proven increase in high flexion grades might be the reason for the higher range of motion that was frequently detected after posterior stabilised prostheses in comparison with posterior cruciateretaining prostheses [22][23][24].…”

“…A significant flexion-gap increase was detected in 90% of patients. Park et al studied 30 patients with severe varus arthritis with a deformity >20°varus or 15°flexion contracture [20]. They detected no effect of PCL release on the extension gap but an increase of 4.5-mm medial and 3.4-mm lateral joint gap at 90°.…”

Comparative evaluation of posterior cruciate ligament in total knee arthroplasty

“…By searching the PubMed database with the strategy of 'TKA PCL gap flexion extension', we finally located eight articles [5][6][7][8][9][10][11][12] concerning the differences in the gap balance after PCL resection after viewing the titles and the reference lists of related articles (Table 2). Among these studies, the results of Kadoya et al 7 and Park et al 10 suggested that the distance of medial gap increased more compared with the lateral gap, in other words, decreasing the degrees of the varus deformity, which are consistent to our work with high distract force (20 and 30 in-lbf). Conversely, Baldini et al's 8 research agrees with the present study that under low distraction force the degree of varus deformity remains the same.…”