Allograft vs. Autograft
When performing an ACL reconstruction, doctors typically use one of a few tendons – the patellar hamstring or, less commonly, the quadriceps tendons – to replace the damaged ligament.  While the tendon is often harvested from the patient’s own body (an autograft), doing so subjects the body to additional injury and more time in the operating room.  For that reason, doctors may choose to use donor tendons (allografts). “You simply pull it out of the freezer and it’s ready to use,” says Brett D. Owens, MD, chief of orthopedic surgery service at Keller Army Hospital in West Point, N.Y. However, using a donor graft carries a small but real risk of disease transmission and research suggests – for active young adults, at least – a higher failure rate.

In a study led by Dr. Owens, researchers at the United States Military Academy in West Point, identified and tracked 120 cadets who had undergone a total of 122 ACL reconstructions prior to entering the academy. The majority – 106 – of the reconstructions used the cadets’ own tendons; the rest used donor tendons. While the cadets were at the academy, 20 of the ACL reconstructions – 12 percent of the reconstructions using autografts and 44 percent of those using donor tendons -- failed, requiring further surgery. The ACL reconstruction using donor tendons also tended to fail earlier than those using autografts.

“Our study is unique since we did not perform the surgeries,” says Dr. Owens. The weakness of the study, he says, is that it did not allow the researchers to control for surgical techniques, rehab protocols or variability in sterilization techniques. He explains that various techniques to sterilize the graft tissue are often used to reduce the transmission of infection. However, sterilization can decrease the grafts’ effectiveness and thus may account for the high failure with allografts.

Although Dr. Owens does use allografts in his practice, based on the findings of this and other studies, he recommends autografts for highly athletic young people.

Other studies are looking at the effectiveness of allografts and other procedures in other populations.

Improving Surgical Treatment
When most tissues are injured, suturing them together and letting nature take its course is often an effective treatment.  But an ACL that is simply sewn together very rarely heals, says Dr. Murray. Although scientists have long questioned why injured ACLs don’t heal, Dr. Murray and her colleagues found a likely answer while examining damaged ACLs from patients who had undergone reconstruction.

While the cells in the severed ACLs were active and working to mount a healing response, the researchers found,  there was no provisional scaffold – or bridge – that normally forms between two torn ends of a ligament enabling them to heal.  When you tear an Achilles tendon, for example, a blood clot forms that serves as a bridge for the cells to form scar tissue and heal the torn tendon, Dr. Murray says.  The ACL’s location within the joint, however, allows the joint fluid to wash away the clot, so that the two torn ends can’t reunite.

Once they learned the cause, they set out to develop a solution – a collagen-based scaffolding that could be implanted at the time of repair. In animal models with torn ACLs, suturing the torn ligament and placing the biological scaffold was proven as effective as ACL reconstruction after 12 months. Furthermore, there was evidence that cartilage damage was less severe in the animals treated with the biological scaffolding, suggesting that future development of osteoarthritis might be lower with the new procedure as well.  

Studies in humans are scheduled to begin soon. The scientists hope the new procedure may  provide an easier way to repair torn ACLs, eliminating the need for grafts, while helping them better understand why ACL injury eventually leads to OA and what measures they can take to help stop OA from developing.