One of the four major ligaments in the knee, the anterior cruciate ligament (ACL) prevents excessive forward movement and rotation of the tibia relative to the femur. Injuries to the ligament typically occur due to rapid deceleration, twisting, or landing during athletic competition. Currently, the standard surgical treatment is a procedure known as ACL reconstruction. This involves the removal and replacement of the torn ACL with a graft harvested from the patient’s own tendons. However, a novel surgical technique developed at the Sports Medicine Research Laboratory may prove to be a better alternative.
Bridge-enhanced ACL repair (BEAR) uses a bioactive scaffold to complement standard suturing techniques. Unlike ACL reconstruction, BEAR seeks to preserve rather than remove the remaining ACL tissue. Post-injury, the ACL cannot heal by itself due to the premature dissipation of the scaffold that naturally forms when blood fills up damaged tissue. However, BEAR surgically implants a substitute collagen-based scaffold that forms a “bridge” between the two torn ACL ends. The patient’s own blood is then injected into this scaffold, providing proteins and growth factors, while promoting clot formation. Within six to eight weeks, the torn ends of the ACL grow back into the scaffold, ultimately replacing it with new tissue.
BEAR presents several benefits over traditional ACL reconstruction. Most notably, it decreases rates of post-traumatic joint pain and stiffness. Moreover, preserving the torn ends of the ACL also offers potential advantages, as the preserved ligament may retain proprioceptive function. During the healing process, small stresses on the ligament tissue can activate proprioceptive fibres, triggering micro-corrections that restore normal knee dynamics and kinematics. However, extraneous factors such as sex can influence the effectiveness of BEAR, highlighting that further research and assessment is still required before BEAR can transition into a surgical standard.
Written by Kevin Ren
References may be found in the journal.