[Analysis of the mechanical function of the cruciate ligaments in antero-posterior knee laxity. An in vitro study].

In order to evaluate the contribution of both anterior (ACL) and posterior cruciate ligaments (PCL) in antero-posterior knee laxity, mechanical tests were performed on 31 fresh-cadaver-knees ranging from 20 to 68 years old. The joints flexed at 90 degrees in a mounting apparatus were placed in a testing machine with the tibia fixed in neutral rotation. The load-displacement curves were then analyzed. The results showed that the tensile strength of the ACL decreased greatly with age whereas its stiffness measured during anterior drawer test remained independent of age and sex. Successive resection of the antero-medial (AM) and postero-lateral (PL) bundles of the ACL demonstrated the AM bundle to be the major structure involved in the limitation of tibial displacement in the anterior drawer test. The amount of tibial shift during the anterior drawer test did not reflect the condition of the ACL, while its resection always induced a strong and significant drop in anterior knee stiffness. Dissection of the PCL was always followed by significant posterior tibial displacement during the posterior drawer test of over 10 mm, which did not permit the experimental apparatus to quantify the posterior load displacement relationship.