Current status and potential of primary ACL repair

Anterior cruciate ligament (ACL) rupture occurs in hundreds of thousands of active adolescents and young adults each year. Despite current treatment, posttraumatic osteoarthritis following these injuries is common in these young patients. Thus, there is widespread clinical and scientific interest in improving patient outcomes and preventing osteoarthritis. The current emphasis on the removal of the torn ACL and subsequent replacement with a tendon graft (ACL reconstruction) stems from adherence to a long-held and widely accepted doctrine that the ACL has only a limited healing response and, therefore, cannot heal or regenerate with suture repair. Recent work has shown that, despite an active biologic response in the ACL after injury, the two ends of the torn ligament never reconnect. Additional studies have detailed findings after placement of a substitute provisional scaffold in the wound site of the ACL injury to bridge the gap and initiate healing of the ruptured ligament after primary repair. This technique, called enhanced primary repair, has significant potential advantages over current ACL reconstruction techniques, including the preservation of the complex attachment sites and innervation of these structures, thus retaining much of the biomechanical and proprioceptive function of these tissues. This manuscript summarizes the recent in vitro and in vivo studies in the area of enhancing ACL healing using biologic supplementation. Subsequent work in this area may lead to the development of a novel approach to treat this important injury.