Total knee arthroplasty ligament balancing and gap kinematics with posterior cruciate ligament retention and sacrifice.

This cadaver study was undertaken to gain insight into the effects that posterior cruciate ligament retention and sacrifice would have on the amount of deformity correction obtained with medial and lateral structure release during total knee arthroplasty. Twenty-seven cadaveric specimens were used to sequentially release medial and lateral structures with and without posterior cruciate support. Each release sequence was tested in full extension and 90 degrees flexion. In full extension, the resulting change into valgus after release of the posterior cruciate ligament, posteromedial capsule/oblique ligament complex, superficial medial collateral ligament, and pes anserinus and semimembranosus tendons was 6.9 degrees, and it increased to 13.4 degrees in 90 degrees flexion. With preservation of the posterior cruciate ligament this decreased to 5.2 degrees in extension and 8.7 degrees in flexion. Changes seen in 90 degrees flexion were significantly greater than those in full extension. For the valgus knee model with release of the posterior cruciate ligament, posterolateral capsule, lateral collateral ligament, iliotibial band, popliteus tendon, and lateral head of the gastrocnemius, 8.9 degrees of change into varus was seen in extension and 18.1 degrees in 90 degrees flexion. With posterior cruciate ligament retention 5.4 degrees and 4.9 degrees of change into varus was seen in extension and flexion, respectively. Significantly less change with retention of the posterior cruciate ligament was seen with both medial and lateral release and more opening of the flexion gap was seen on the release side of the joint for all groups except those with lateral release with sacrifice of the posterior cruciate ligament.