Influence of Posterior Cruciate Ligament Resection on Knee Balancing and Bone Resection Thickness in Patients Undergoing Robotic-Assisted Total Knee Arthroplasty: A Prospective Study

Abstract

Introduction The decision to retain or sacrifice the posterior cruciate ligament (PCL) during total knee arthroplasty (TKA) is debated among surgeons. This study aimed to determine the effects of PCL removal on gap balancing, bone-cut thickness, and component positioning. Methods This prospective study included 70 consecutive patients with varus deformity undergoing Mako (Stryker Orthopaedics, Fort Lauderdale, FL, USA) robot-assisted TKA between January 2022 and June 2022. Flexion and extension gaps were initially captured with the PCL intact, using the mechanical alignment start-point, after which the knees were balanced using the functional alignment philosophy. Following this, the PCL was sacrificed, and gaps were recaptured to assess the dynamic change in balance and bone cut thickness, with statistical analyses performed. Results The mean age of the population was 59.46 years (SD = 9.2), with a female preponderance (N = 50, or 71.40%). PCL resection significantly increased the mean flexion gap in the medial compartment from 15.7 mm (SD = 2.36) to 18.8 mm (SD = 1.83), and in the lateral compartment from 22.7 mm (SD = 1.66) to 24.5 mm (SD = 1.62), with minimal change in the extension gap. Rebalancing after PCL resection resulted in a reduction in posterior femoral bone resection thickness, with the posteromedial cut decreasing from 9.6 mm to 7.1 mm, and the posterolateral cut from 4.8 mm to 2.7 mm. Conclusion This study demonstrates that PCL resection consistently leads to a preferential increase in the flexion gap, with minimal impact on the extension gap. The flexion gap increased more significantly in the medial compartment than in the lateral compartment, in approximately a 3:2 proportion. Additionally, PCL resection was associated with decreased posterior femoral bone resection thickness and a trend toward reduced femoral component external rotation.