The role of the posterior cruciate ligament (PCL) remains controversial in total knee arthroplasty (TKA), with some surgeons who believe in PCL sacrifice and substitution and others who believe in PCL preservation for stability. Manufacturers have developed both cruciate-substituting/posterior stabilized (PS) implants typically used when the ligament is sacrificed and cruciate retaining (CR) implants designed for ligament preservation. However, studies demonstrate excellent clinical results with CR implants despite PCL sacrifice. This study sought to determine functional stability differences between PS and CR TKAs following PCL sacrifice. Eighteen (9 matched pairs) subjects with either a PS or CR TKA and sacrificed PCL and a normal contralateral knee were subjected to physical exam and gait analysis (walking, stair ascent and descent) using a staircase model, passive reflective arrays and an optoelectric system. No differences were detected between the two groups among any of the measured parameters (knee flexion angle, knee flexion moment, knee power absorption, pelvic tilt). PCL sacrifice in a well-balanced cruciate retaining TKA did not result in instability during stair descent based on gait parameters. The decision to use a posterior stabilized design when faced with an incompetent PCL intraoperatively should be based on factors other than anticipated instability.
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