Effect of Graft History on Results of ACL Surgery

Severe damage to the anterior cruciate ligament (ACL) of the knee often requires reconstructive surgery. The surgeon uses graft tissue taken from a donor bank (called an allograft) or harvested from the patient (an autograft). But the reported failure rate for this surgery is as high as 20 per cent. That's one out of every five patients -- an unacceptable level for any surgeon.

Taking a closer look at the studies published on this topic, there seems to be about a 12 per cent failure rate for allograft tissue. It's possible that some specific factor about the allograft is responsible for these failures.

But as the authors of this study point out, less than one-fourth of the studies on ACL reconstructive surgery even report information about the history of the allografts used in their patients. And it could turn out to be an important variable in surgical success.

If you are thinking about having ACL reconstructive surgery with an allograft, you may wonder what should I know about donated tissue? It may be something you want to discuss with your surgeon. Ask about the risks, benefits, and expected long-term outcomes for the graft tissue used. As the authors of this report point out, surgeons may well want to pay a bit more attention to matching allograft tissue to each individual patient.

For example, donor tissue can come from patients of all ages. In the case of tendons or ligaments, there are age limits. The donor can not be more than 60 years old. Studies have not been done to show if matching the patient age to the age of the allograft is important.

But it makes sense that the stiffness and load donated tissue can withstand should match the level of activity of the recipient (patient receiving the graft tissue). And since the graft can come from one of several sources (e.g., patellar tendon, hamstring tendon, Achilles tendon, tibialis posterior, peroneus longus, fascia lata), it's possible that age, tensile strength of the tissue, and biomechanical load each tissue can withstand before failure should all be investigated and compared.

Then there is the matter of how the graft tissue is prepared, processed, and stored for use. How was the graft tissue sterilized? It could make a difference. Did the graft come from an accredited tissue bank? There is an organization called the American Association of Tissue Banks (AATB) that sets standards for tissue processing and donor eligibility. But there's no law that requires tissue banks to follow their guidelines.

Surgeons are advised by the American Academy of Orthopaedic Surgeons (AAOS) to use donor tissue only from tissue banks that are inspected and approved by the American Association of Tissue Banks (AATB) or the Food and Drug Association (FDA). AATB authorized donor banks test carefully to make sure the donor tissue is free of diseases, viruses, and infections such as HIV or hepatitis. The tissues are inspected, cleaned, and sterilized before being stored for later use.

It's important to know when was the last inspection. A one-time inspection 10 years ago is not sufficient. The donor bank should be routinely inspected and pass that inspection. The bank should be providing tissue that has been processed according to the most up-to-date guidelines published by the AATB. These same guidelines are used by the FDA.

Even with donor tissue from accredited sources, there still remain many unknowns. For example, what's the effect of all the processing, sterilization, and storage on the strength of the tissue? There is some concern that the process of irradiating the tissue at high enough doses to kill viruses can damage the collagen fibers and weakening them.

What is the oldest age of tissue that can be used in patients? Should the donor graft be matched by age or should the surgeon try to use tissue from a donor who was younger at death than the patient now receiving the tissue? If older donor tissue is used, are there age limits? What are those limits?

After reviewing published studies on this topic, the authors make several recommendations. First, surgeons are advised to learn more about how donor tissue is processed and preserved. Second, with this information, they can advise their patients about the advantages and disadvantages of allograft versus autograft tissue for ACL reconstruction. Third, surgeons may want to pay closer attention themselves to specific patient factors for both the donor and the recipient (their patient). And finally, more studies are needed in this area to improve success rates and patient outcomes.

Reference: Robby S. Sikka, MD, et al.Anterior Cruciate Ligament Allograft Surgery. Underreporting of Graft Source, Graft Processing, and Donor Age. In The American Journal of Sports Medicine. March 2011. Vol. 39. No. 3. Pp. 649-655.

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