Retention or sacrifice of posterior cruciate ligament has no effect on in vitro kinematics in medial pivot total knee arthroplasty.

Abstract

The role of the posterior cruciate ligament remains debated, particularly in medial pivot designs intended to functionally substitute the posterior cruciate ligament. While some manufacturers recommend posterior cruciate ligament resection, evidence regarding its biomechanical relevance in medial pivot total knee arthroplasty is limited. This in vitro study evaluated knee kinematics in seven cadaveric knees implanted with a mechanically aligned medial pivot total knee arthroplasty (GMK Sphere). Each specimen was tested dynamically (30°-130° flexion) under three conditions: native knee, medial pivot with posterior cruciate ligament retained and with posterior cruciate ligament resected. Kinematic parameters (anterior-posterior translation, tibial rotation, patellar shift and tilt) and quadriceps force were recorded using a 3D optoelectronic system in a validated dynamic knee rig. Compared to native knees, medial pivot total knee arthroplasty increased anterior tibial translation and altered tibial rotation (p < 0.001), regardless of posterior cruciate ligament status. Patellar shift showed less medialization in deep flexion with posterior cruciate ligament retention in comparison to native conditions (R² = 0.20, p < 0.001). Quadriceps force differed from the native state but was unaffected by posterior cruciate ligament status; force patterns were primarily determined by the native knee (R² = 0.90, p < 0.001). Posterior cruciate ligament retention in medial pivot total knee arthroplasty does not significantly affect femorotibial or patellofemoral kinematics. The highly congruent medial design appears to reduce the functional importance of the posterior cruciate ligament. Therefore, intraoperative decisions regarding posterior cruciate ligament management may be made less on concerns about kinematic compromise. N/A.