Biological Augmentation of Anterior Cruciate Ligament Grafts

Anterior cruciate ligament (ACL) injury is a common sports injury. Generally, arthroscopic ACL reconstruction is performed because of the poor self-healing ability of the injured ACL. In the healing process after ACL reconstruction, tendon graft remodeling and incorporation at the tendon-bone junction are important factors for healing success. It is commonly accepted that the strength of the tendon graft attenuates immediately after ACL reconstruction and gradually increases thereafter. This gradual maturation of the grafted tendon is considered a cause for graft failure or elongation after ACL reconstruction. On the other hand, the bone-tendon junction is the weakest region after ACL reconstruction. In native anatomy, fibrocartilaginous tissue binds the ACL and bone, but this tissue does not undergo remodeling during reconstruction. A fibrous scar-like tissue often binds the grafted tendon and bone, ultimately affecting the stability of the graft in the bone tunnel and contributing to ACL rerupture. To solve this and other issues related to ACL reconstruction, extensive basic research has been conducted in recent years regarding biological or tissue augmentation, including studies on stem cells, growth factors, cytokines, and synthetic grafts. Alternatives for quicker graft maturation and more robust tendon-bone junction remodeling have been reported in animal models. These investigative results show promise for more aggressive rehabilitation techniques in the near future that will facilitate an earlier return to sports for patients with ACL injury.