ISOLATED SECTIONING OF THE MEDIAL AND POSTEROMEDIAL CAPSULAR LIGAMENTS IN THE POSTERIOR CRUCIATE LIGAMENT-DEFICIENT KNEE - INFLUENCE ON POSTERIOR TIBIAL TRANSLATION

This study was undertaken to determine the contribution of various str uctures in the posterior cruciate ligament-deficient knee in resisting posterior tibial translation. With ''isolated'' injuries to the poste rior cruciate ligament, the amount of posterior translation will decre ase with the posterior drawer test as the knee is taken from neutral t o internal tibial rotation. The present study was performed to conclus ively determine the anatomic structure responsible for this clinical o bservation. The TestStar device was used to perform single-plane poste rior drawer tests in 14 cadaveric knee specimens. The tests were perfo rmed with the knee in neutral tibial rotation and in 20 degrees of int ernal tibial rotation. The intact knee was tested and then the knee wa s tested after sequential sectioning of the menis-cofemoral ligaments, the posterior cruciate ligament, the posteromedial capsule, and the s uperficial medial collateral ligament. With the knee in neutral rotati on, posterior translation continued to increase as each structure was sectioned. With the knee in internal tibial rotation, posterior displa cement was significantly less than in neutral rotation for each state until the superficial medial collateral ligament was sectioned; poster ior translation was increased after its sectioning. Our data demonstra te that the superficial medial collateral ligament is the structure re sponsible for a decrease in posterior tibial translation in the poster ior cruciate ligament-deficient knee.