Sheldon Cohn, M.D.

"You have torn your anterior cruciate ligament".  After receiving that diagnosis from your  Orthopaedic Surgeon you have discussed your treatment options and during that discussion you were told that if you have surgery that your ligament would be replaced by a graft.

This article is an attempt to help explain what the different ligament graft materials are.  Grafts are used to replace the ligament because the ligament will not heal on it's own, even if it is repaired.  Graft tissue can be obtained from your body, known as  autografts; or from an organ donor, known as a cadaver graft or allograft.  Once placed in the knee the body uses grafts as a scaffold to build new tissue.  The tendon tissue is gradually replaced by ligament tissue.  Attempts have been made in the past to use artificial ligaments, such as carbon fiber or Gortex grafts.  Unfortunately, to this point they have all been found to fail over time.

We choose graft material that has been compared to the anterior cruciate ligament, (ACL), in terms of biomechanical properties. The middle one third of the patella tendon and its bony attachments, the achilles tendon, hamstring tendons and part of the quadriceps tendon are some of the tissues used.  Either the rest of the tendon remaining after graft harvest will recover to adequate strength or the harvested tendon is not needed for someone to function well.  For example, the patella tendon remaining  grows bigger and stronger after taking out the middle third so that when your knee is ready to begin sports again the patella tendon is strong enough.  Surgeons who use the hamstring tendons feel that either the tendon regrows or is not needed to obtain the level of post op function desired. 

We obtain allograft tissue from tissue banks.  These corporate concerns harvest the tissue from tissue donors and have strict criteria in terms of donor age, health, harvesting techniques and tissue preparation and preservation.  At this time we think that the risk of bacterial infection from a graft is about 1 in 600,000.  The risk of a viral infection such as hepatitis or AIDS is projected at 1 in a million.  We do not think rejection is a problem as there are few cells in the tissue grafts.  They are mainly a protein scaffold called collagen.  Why not just use an allograft anterior cruciate ligament?  Everyone's ligament has a different length and structure.  We do not have a great technique for adjusting the length of an implanted ligament, as we do for tendons.

Graft tissue choice depends on patient age, anatomy, previous surgery, other knee problems such as arthritis and expectations regarding post op activity level.  The Orthopedic Surgeon's training, experience and opinion based upon their review of the scientific data all enter into their recommendations regarding graft choice.  There are risks and benefits to each of the tissue graft choices and a thorough discussion of all of those is beyond the scope of this article.

The most important thing to keep in mind as a patient is that the success of the surgery depends to a greater degree on the procedure being done precisely by the surgeon and the patient having realistic expectations and diligently following their rehabilitation protocol than the type of graft used.

Sheldon Cohn, M.D.

Dr. Cohn is a sport medicine fellowship trained Orthopaedic Surgeon who has been performing Anterior Cruciate Ligament reconstruction surgery for twenty years.  He practices at Orthopaedic Associates of Virginia