ABNORMALITY OF THE CONTRALATERAL LIGAMENT AFTER INJURIES OF THE MEDIAL COLLATERAL LIGAMENT - AN EXPERIMENTAL-STUDY IN RABBITS

The right medial collateral ligament of ninety-four adult, female rabbits was transected operatively. At three, six, fourteen, or forty weeks after the operation, the uninjured, contralateral (left) medial collateral ligaments of seventy-eight of the animals were tested biomechanically and compared with the left medial collateral ligaments of thirty-three normal female rabbits. The diameters of the mid-substance collagen fibrils in the medial collateral ligaments were also measured in the uninjured, contralateral hindlimbs of four animals at each interval and compared with the fibril diameters in three normal animals at each of three corresponding intervals. Subtle but significant differences between the uninjured, contralateral and the normal medial collateral ligaments with regard to biomechanical properties of collagen fibril diameters were found at all time-intervals. These results support the notion of a significant effect on the contralateral ligament after an injury to the medial collateral ligament and suggest that contralateral ligaments cannot be considered as a normal control group even in this relatively benign model of knee injury. CLINICAL RELEVANCE: These findings have two important clinical implications. First, studies of the biomechanical properties and collagen diameters of injured ligaments that have been performed with the use of an intrinsic contralateral control group should be interpreted in light of the findings reported here. Second, it is possible that this contralateral effect may also be seen in humans. Clinical observations have suggested that this concern may be valid and that the practice of reporting only side-to-side differences for ligament characteristics may have to be re-evaluated.