New Bioengineered ACL May Provide Optimal Treatment for Torn ACLs
Researchers at Northwestern University have developed artificial anterior cruciate ligaments, better known as ACLs, to replace torn ligaments—a common sports injury. The bioengineered ACLs are made from braided polyester fibers, which are comparable in tensile strength to the actual ACL, and thus capable of stabilizing the knee.
ACLs connect the femur (thigh bone) to the tibia (the larger of the two leg bones). Once an ACL is ruptured or completely torn, it does not heal, mainly because it’s an intra-articular ligament that’s located within the knee joint. When extra-articular joints are injured, like the medial collateral ligament (MCL), they have the ability to repair itself with rest. A blood clot forms, which serves as the bridge to connect the tear to the bone, and healthy tissue grows to replace the gap. Within the knee joint, any clots that form get washed away with the constant influx of synovial fluid, inhibiting ACLs from being healed.
Conventional treatment for a torn ACL is reconstructive surgery using grafts from the patellar tendon (kneecap). Resulting surgery can cause lasting soreness and tenderness and permanently weaken the patellar tendon. In some cases, the weakened tendon may rupture completely. Even without any major complications and years of physical therapy, natural ease of movement is never fully achieved.
Using rabbit models, the scientists drilled holes into the femur and tibia. Prior to inserting the bioengineered ACL into each receiving end, the fibers were first dipped into a concoction of hydroxyapatite (calcium derivatives naturally found in teeth and bones) nanocrystals and a porous antioxidant biomaterial. Upon anchoring the ends, the rabbits’ nearby bone and tissue cells began to resettle into the pores of the mixture. The researchers hope the ends of the bioengineered ACL can be fully integrated into the femur and tibia given enough time.
The prospect of incorporating an artificial bioengineered ACL to natural bone is promising news for the scientists. However, more studies need to be conducted before human trials begin.