Medial restraints to anterior-posterior motion of the knee
Sullivan, D.; Levy, I.M.; Sheskier, S.; Torzilli, P.A.; Warren, R.F.
Journal of Bone and Joint Surgery. American Volume 66(6): 930-936
1984
ISSN/ISBN: 0021-9355 PMID: 6736094 Document Number: 223486
The motion of cadaver knees before and after section of the medial structures and anterior cruciate ligament were investigated. The knees were tested using a 5.degree.-of-freedom in vitro knee-testing apparatus that measured anterior-posterior, medial-lateral and axial displacement as well as internal-external and valgus-varus rotation. The flexion angle could be varied but was fixed for each individual test. A 125-N anterior-posterior force was applied perpendicular to the tibial shaft and the resulting motion of the knee was measured. In 5 knees the anterior cruciate ligament was cut 1st, followed by progressive cuts of the structures on the medial side (superficial medial collateral ligament, deep medial ligament, oblique fibers of the superficial medial ligament and the posteromedial part of the capsule). In 5 knees the medial structures were progessively cut first, followed by section of the anterior cruciate ligament. Tests were performed after each cut. With an intact anterior cruciate ligament, progressive cutting of the medial side had no effect on anterior and posterior displacements. When section of the medial structures followed cutting of the anterior cruciate ligament, anterior displacement exceeded that seen after isolated section of the anterior cruciate ligament. The anterior and posterior load-tests were repeated with the tibia fixed in 5.degree. of internal and 5.degree. of external rotation. Fixed external rotation had no effect on anterior and posterior displacements. Fixed internal rotation significantly decreased anterior displacement only when both the anterior cruciate ligament and the medial structures were cut. The amounts of tibial rotation and tibial torque resulting from the applied anterior and posterior forces were low compared with our previous results, and this was attributed to decreased constraints on motion of the knee in the current testing apparatus.