Optimization of knee ligament position for lateral extraarticular reconstruction

Abstract

A kinematic study of five adult cadaver knees was performed to determine the behavior of the separation distances connecting all combinations of a network of points on the lateral side of the knee. Measurements were obtained between each pair of points at the level of the capsule for seven different angles of flexion ranging from 0 to 125°. The data obtained allow further analysis of tendinous reconstructions attached to each pair of points as regards stretching and laxity through out a normally occurring range of motion. The Rowe- Zarins combined intra- and extraarticular reconstruc tion, the Sling-and-Reef procedure, and other extraar ticular methods were analyzed in light of these data. Attachment of a reconstruction at the proximal an terolateral tibia, in front of Gerdy's tubercle paired with femoral attachment high and proximal to the origin of the lateral collateral ligament on the femur, was ob served to demonstrate favorable behavior for several reasons. First, such a check reign represents an ob vious, major restraint to anterior translation as it is positioned well posteriorly on the femur and anteriorly on the tibia. Second, the attachment points were seen to demonstrate maximum separation between 15 and 45° of flexion, thereby not being forced into any unde sirable stretching if the knee were to move normally throughout the other portions of the motion cycle. Consequently, obligate stretch with full flexion or full extension would appear unlikely. Separation distances between attachment points were highly dependent upon changes in the femoral fixation point and much less variable as a result of tibial attachment position. Placing the knee through a flexion-extension range of motion with the tibia held unnaturally in external rotation, which is frequently done in the operating room, violates the normal kinematic pattern of knee motion. As a result, unsuitable attachment points may erro neously appear well behaved. This observation may offer one important explanation for long-term stretching of a ligament reconstruction which appeared satisfac torily tight and strong at the time of surgery. The data obtained allow proper positioning of anterolateral re constructions so that this mode of stretching will not be encountered as a result of normal knee motion.