Posterior Cruciate Ligament Resection Does Not Consistently Increase the Flexion Space in Contemporary Total Knee Arthroplasty.

Abstract

It is accepted dogma in total knee arthroplasty (TKA) that resecting the posterior cruciate ligament (PCL) increases the flexion-space by approximately 4mm. Unfortunately, this doctrine is based on historical studies of limited size with variable technique. The aim of this study was to determine the effect of PCL-resection on in vivo tibiofemoral joint space dimensions in a cohort of modern TKAs. Tibiofemoral joint space measurements were made during 129 standardized TKAs by two arthroplasty surgeons. A medial parapatellar approach, computer navigation and provisional bone cuts were performed in all cases with particular attention to preserving PCL integrity. The tibiofemoral gap was measured with a calibrated tension device at extension, 45-degrees, and 90-degrees before and after complete PCL-resection. 51% of patients were female (66/129) with mean age and BMI of 69.5 years and 34.2 kg/m², respectively. After PCL-resection, mean change in center joint space dimension increased 0.33mm at extension, 0.95mm at 45-degrees, and 1.71mm at 90-degrees (P < .001). The 90-degree flexion-space opened ≥4mm in only 10% of patients. Dividing the flexion-space change by femoral implant dimension to account for patient size, the flexion-space at 90-degrees significantly increased more in females compared to males (P = .020). The tibiofemoral joint space increased progressively from extension to mid-flexion through deep-flexion after PCL-resection, yet was substantially less than reported in historical studies. However, large variation in flexion-space opening was observed with some patients failing to increase the flexion-space whatsoever with PCL-resection. This runs counter to conventional TKA understanding and should be considered in modern surgical education. Therapeutic Level III.