ACL Repair? New Surgical Techniques to Heal a Torn ACL

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An ACL tear is a common sports-related knee injury. Courtney Keating / Getty Images

A torn anterior cruciate ligament (ACL) is a common sports-related injury, especially in high school and college age athletes.  One of the challenging aspects of recovering from a torn ACL, is that there has been no good way to repair a torn ligament.  Rather than repair the torn ligament, the surgery used for treatment of an ACL tear is called an ACL reconstruction.

ACL reconstruction surgery is performed by taking a graft of tissue (either ligament or tendon) and transferring this into the knee joint to take the place of the torn ACL.

  Common places to obtain the ACL graft include:

  • Hamstring tendon
  • Patellar tendon
  • Allograft (cadaver) donor

Each of these options has advantages and disadvantages, and there is no perfect option.  Many surgeons have particular preferences, but there is no clear best graft.  There is good evidence that donor grafts are probably not ideal in very high demand patients (college or professional athletes), but there is great debate among orthopedic surgeons about which option is best.

However, all surgeons would agree that the ideal solution would be to find a way to repair the torn ACL, and not have to use other tissue to reconstruct the ligament.  If only there were a way to heal a torn ACL...

Torn ACLs Don't Heal and Aren't Repaired

A torn ACL can't heal for a few reasons, but the primary issue seems to be the local environment of the inside of the knee joint.  Other ligaments in the body heal just fine.

  Torn ligaments after an ankle sprain or an MCL tear seldom require surgery.  Unfortunately, the location of the ACL in the knee joint makes it difficult for the body to complete a healing process.

Research has shown that ACLs try to heal--in fact the proliferation of healing cells is similar after an ACL tear as an MCL tear.

  The difference seems to be that the normal blood clotting around the torn ligament is washed away by knee joint fluid.  This clot is necessary to form a type of scaffold for the healing ligament to repair itself, but in the ACL, the location inside the knee joint dooms the healing process.

Even if a surgeon sews together the torn ends of a damaged ACL, the body can't repair the damaged ligament, and the surgery fails more than 90% of the time.  Researchers had to find a way to provide the damaged ACL with the right environment to heal.

Bridge-Enhanced ACL Repair

Researchers are developing new techniques to create an environment around the torn ACL that would allow for the ligament to heal.  The new surgery, called a bridge-enhanced ACL repair, uses a collagen scaffold to surround the torn ends of the ACL.  The ends of the ligament are sewn together, and the area is injected with platelet rich plasma (PRP).

The potential advantages of ACL repair over reconstruction are significant.  Foremost, a repaired ACL would be most likely to restore knee mechanics back to normal, a concern with ACL reconstruction.

  Many techniques have been developed, such as double-bundle reconstruction, to improve knee mechanics after ACL reconstruction, but the effectiveness of these are debatable.

The second major advantage is the lack of having to damage normal structures to obtain a graft--no removing a hamstring tendons or disrupting the patellar ligament.  In addition, there aren't risks of a weak graft or disease transmission seen with donor tissues.

Bottom Line: Is It Better?

The is no doubt that in theory ACL repair would be far preferable to ACL reconstruction.  Unfortunately, it is too soon to know if the success of this surgery is as good as traditional ACL reconstruction.  Researchers are just beginning to try this surgery in people, and many have concerns about whether or not this will be successful.  While traditional ACL reconstruction has potential problems, it is a very successful surgery, and before a new technique can be recommended it has to be shown to be comparably effective (and hopefully better).  Hopefully over the coming years we will know more if ACL repair can be an effective option for athletes who sustain this injury.

Sources:

Stanton T. "Award-Winning Research May Make ACL Healing Without Reconstruction Possible" AAOSNow. February 2013.

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