What is the Optimal Posterior Cruciate Ligament Tension to Achieve Patient Satisfaction in Cruciate-Retaining Total Knee Arthroplasty?

Abstract

Achieving adequate posterior cruciate ligament (PCL) tension is important during PCL-retaining total knee arthroplasty (CR-TKA), but the effect of PCL release on this tension is unpredictable. This study assessed the relationship between postoperative PCL laxity and patient satisfaction at a 2-year follow-up. There were 44 varus osteoarthritis knees undergoing CR-TKA included. The PCL tension was adjusted by resizing the femoral component and modifying the posterior tibial slope, without PCL release. Postoperative PCL laxity at 90° of knee flexion was defined as the difference in radiographic anterior-posterior tibial translation with or without an 80-Newton posterior load at the tibial tubercle measured using a load device. Four subgroups were defined according to the PCL laxity: laxity ≤0 mm (n = 5); 0 mm < laxity ≤2 mm (n = 19); 2 mm < laxity ≤4 mm (n = 10); and laxity >4 mm (n = 10). The effect of PCL laxity on the 2-year postoperative 2011 Knee Society Score was determined. The femoral component was downsized in 27 of 44 knees, while the posterior tibia slope was increased in 6 of 44 knees, but no PCL was released intraoperatively. The 2011 Knee Society Score subscores improved significantly from preoperatively to postoperatively, and patients reported "neutral satisfaction" or better after 96% of operations. The mean PCL laxity was 2.3 mm on postoperative stress radiographs, and postoperative satisfaction scores were significantly highest in the subgroup with 2-4 mm laxity. CR-TKA was successfully performed without PCL release. Moderate PCL laxity (2-4 mm) achieved excellent postoperative satisfaction.