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

It is broadly supposed that in total knee arthroplasty, the flexion/extension gap ratio is increased after resection of the posterior cruciate ligament (PCL). However, studies are rare and results are inconsistent. Therefore, this study was conducted to determine whether PCL release regularly increases the flexion gap. Data from 50 consecutive posterior stabilised knee prostheses were analysed retrospectively. Using imageless computer navigation, the joint-gap width was measured over the entire range of motion before and after PCL release. PCL release had no effect on the extension gap, but it increased the flexion gap significantly. An increase of > 3 mm occurred in 36% of patients and of > 5 mm in 12%. No clinically relevant effect (< 2 mm) was found in 44% of patients. PCL release increased the flexion/extension gap ratio on average, but the individual effect could not be predicted. Therefore, we recommend PCL release before the femoral resections are performed, as this step mainly determines the ratio between extension and flexion gap.