A New Procedure Shows Promise for Treating Knee Ligaments

Image Courtesy:  Boston Children's Hospital

Over hundreds of thousands of anterior cruciate ligament (ACL) injuries occur each year. An ACL tear is a serious sports injury which may suddenly end an athlete’s career. ACL reconstruction is probably the most common surgery athletes undergo.

However, the ACL reconstruction procedure is invasive and the possibility of re-tear is quite high. Around 80% of patients also develop arthritis 15 years after the operation even if the reconstruction was successful.

A new technique called Bridge-Enhanced (ACL) Repair (BEAR) has been developed and tested by a team of doctors led by Dr. Martha Murray, an orthopedic surgeon working at the Boston Children’s Hospital. Instead of using tendon grafts, they stimulated the torn ACL to repair itself.

Currently used procedure requires the removal of the torn ligament and replacing it with a tendon graft. The graft is usually taken from the patient’s own hamstring. A tunnel is made both through the base of the femur and the top of the tibia. The grafted hamstring is inserted through both holes, imitating the position of the original ACL. A screw and a grappling hook are placed on either end to secure the graft in place. Over time, the ACL will regrow and use the graft as support to create a new, strengthened ACL.

However, aside from the considerable risk or re-tear and earlier signs of arthritis, the patient also has to heal the grafted tissue from their hamstring, prolonging their overall recovery time. With the BEAR procedure, nothing is harvested from the person’s tissues.

When utilizing the BEAR procedure, sutures are placed on the torn ACL and through the base of the femur. A sponge made of special proteins is placed in the gap between the femur and the torn ACL. This sponge acts as a bridge for the ACL to grow into. The sponge is soaked with blood from the patient to jumpstart the ACL’s repairing process. After that, the sutures are used to pull the torn ACL into the sponge.

After a few weeks, the torn ends of the ACL will grow into the sponge, replacing it with repaired tissues and reconnecting the bones similar to how the original ACL did.

All of the 10 patients who underwent the BEAR procedure have regrown new ACLs without any problems. The team now thoroughly observes the post-surgery conditions and performances of all the patients before they proceed to the next phase of the development. If all goes well, the procedure may be widely available in 3 to 4 years.

The repaired ACL is expected to work as well as those which used tendon grafts. The team hopes that BEAR will reduce the time it takes to recover from the operation and also decrease the risks of arthritis in patients after recovering from the injury.