PARTIAL POSTERIOR CRUCIATE LIGAMENT RELEASE IN TOTAL KNEE ARTHROPLASTY MITIGATES EXCESSIVE ROLLBACK WITHOUT COMPROMISING IMPLANT FIXATION

Introduction Balancing the posterior cruciate ligament (PCL) remains challenging in total knee arthroplasty (TKA). Excessively tight PCL can limit range of motion, cause excessive femoral rollback, and induce anterior implant liftoff. While selectively releasing a tight PCL can reduce rollback during passive flexion, the effects of PCL releases on functional knee kinematics and implant fixation have not been evaluated. Therefore, our goal was to quantify the impact of PCL releases on passive TKA kinematics, functional TKA kinematics, and implant fixation. Methods We created patient-specific musculoskeletal and finite element (FE) models of 15 subjects (4 women; 50–73 years) who received a cruciate-retaining TKA and underwent motion analysis during stair ascent and descent one year postoperatively. To virtually reproduce the implantation, we aligned the CT-derived bone geometry and the reverse-engineered implant geometry to biplane radiographs. The musculoskeletal models included 12 knee ligament bundles, with five anterolateral and five posteromedial PCL fibers. The FE models incorporated CT-based non-homogeneous bone material properties. We assessed the effect of releasing the anterolateral, posteromedial, or all fibers of a tight PCL on 1) the anterior-posterior tibiofemoral kinematics from 0° to 90° passive flexion, 2) the functional tibiofemoral kinematics during stair ascent/descent, and 3) the bone-implant micromotion during stair ascent/descent, as a marker of implant liftoff. Results During passive flexion and stair ascent/descent, posteromedial PCL releases decreased posterior rollback between 20° and 90° flexion, anterolateral releases reduced posterior rollback across the full arc of motion. Full PCL releases led to paradoxical anterior rollback on the medial side. Bone-implant micromotion decreased most with anterolateral and full PCL releases. Discussion Partial release of the anterolateral bundle provides the best compromise for limiting excessive PCL tightness by preserving physiological posterior rollback while maintaining stable fixation.