Medial collateral ligament healing one year after a concurrent medial collateral ligament and anterior cruciate ligament injury: an interdisciplinary study in rabbits.

The optimal treatment for concurrent injuries to the medial collateral and anterior cruciate ligaments has not been determined, despite numerous clinical and laboratory studies. The objective of this study was to examine the effect of surgical repair of the medial collateral ligament on its biomechanical and biochemical properties 52 weeks after such injuries. In the left knee of 12 skeletally mature New Zealand White rabbits, the medial collateral ligament was torn and the anterior cruciate ligament was transected and then reconstructed. This is an experimental model previously developed in our laboratory. In six rabbits, the torn ends of the medial collateral ligament were repaired, and in the remaining six rabbits, the ligament was not repaired. Fifty-two weeks after injury, we examined varus-valgus and anterior-posterior knee stability; structural properties of the femur-medial collateral ligament-tibia complex; and mechanical properties, collagen content, and mature collagen crosslinking of the medial collateral ligament. We could not detect significant differences between repair and nonrepair groups for any biomechanical or biochemical property. Our data support clinical findings that when the medial collateral and anterior cruciate ligaments are injured concurrently and the anterior cruciate ligament is reconstructed, conservative treatment of the ruptured medial collateral ligament can result in successful healing.

Effect of growth factors on matrix synthesis by ligament fibroblasts.

Although it has been reported that several growth factors modulate soft-tissue healing, the specific effects of growth factors on protein synthesis during ligament healing have not been widely investigated. In this study, we examined the effects of basic and acidic fibroblast growth factors, transforming growth factor beta 1, and epidermal growth factor on collagen and noncollagenous protein synthesis by cultured fibroblasts from medial collateral ligament and anterior cruciate ligament in vitro. Uptake of tritiated proline was used to measure synthesis of collagen and noncollagenous protein, and sodium dodecyl sulfate-polyacrylamide gel electrophoresis was used to analyze the type of collagens synthesized. Our data showed that transforming growth factor beta 1 increased both collagen and noncollagenous protein synthesis by medial collateral and anterior cruciate ligament fibroblasts on a dose-dependent basis. Collagen synthesis by cultured fibroblasts from the medial collateral and anterior cruciate ligaments was increased by treatment with transforming growth factor beta 1 by as much as approximately 1.5 times that of untreated controls. Although the response to transforming growth factor beta 1 by anterior cruciate ligament fibroblasts was equal to that by medial collateral ligament fibroblasts, the amounts of matrix proteins synthesized by anterior cruciate ligament fibroblasts were approximately half of that by medial collateral ligament fibroblasts. The increase was mostly in type-I collagen. Treatment of anterior cruciate ligament fibroblasts with epidermal growth factor increased collagen synthesis by approximately 25% but had little effect on medial collateral ligament fibroblasts. Neither basic nor acidic fibroblast growth factor increased either collagen or noncollagenous protein synthesis. These findings suggest that topical application of transforming growth factor beta 1, alone or in combination with epidermal growth factor, may have the potential to strengthen the ligament by increasing matrix synthesis during its remodeling and healing processes.