Posterior Cruciate Ligament Effects on the Flexion Space in Total Knee Arthroplasty

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Abstract
Twelve fresh frozen anatomic specimen knees were used in this study to measure changes in the tibiofemoral joint gaps after sacrificing the posterior cruciate ligament. Joint gap changes were measured using a motion tracking device in full extension and at 45° and 90° flexion. Tibiofemoral gaps were measured with no external compressive loads and under tension to define the flexion gap, the space available to be filled by components. After initial anterior cruciate ligament removal, meniscectomy, and a 1-cm tibial plateau cut, sacrifice of the posterior cruciate ligament caused significant differences in the flexion gap. At 90° flexion the tibia distracted from the femur 5.26 ± 1.9 mm (range, 3.2-9.1 mm) at rest and 6.4 ± 2.5 mm under tension. No differences in the joint space were calculated in full extension under either loading case. The authors conclude that a major result of posterior cruciate ligament sacrifice is the creation of a larger flexion gap. This result provides insight into relative joint line changes that can occur after posterior cruciate ligament sacrifice. It also suggests the need for greater attention to flexion stability when sacrificing the posterior cruciate ligament and rethinking the role of posterior cruciate ligament release in the management of pure, primary flexion contracture.