Injuries to the anterior cruciate ligament (ACL) of the knee are all too common in athletes. But they can also occur in older, active adults. What type of tissue graft works best? Should it be an autograft (taken from the patient) or an allograft (donor tissue from a donor bank)?
Besides the allograft vs. autograft decision, there are two popular places where the tissue can be harvested. The first is from the patellar tendon just below the kneecap. This graft is referred to as the bone-patellar tendon bone (BPTB) graft. As the name suggests, the harvested tendon comes with a tiny piece of bone.
The second is a hamstring graft. Tissue is taken from two separate sites of the hamstring muscle. Each graft is folded over to form a quadruple (four-part) graft. This is the strongest graft and referred to as quadruple hamstring graft.
Either source of tissue (patellar tendon or hamstring) can be an autograft or allograft. There are advantages and disadvantages for each one. The authors of this article (two orthopedic surgeons from the Department of Orthopaedic Surgery and Sports Medicine at the University of Kentucky) state their preferences and explain their thinking.
Here's a quick recap of their preferences. We'll fill you in on more details right after the list:
Bone-patellar tendon bone autografts are preferred for young (less than 22 years old), active, high-level athletes who play year-round sports.
Hamstring autograft is recommended for patients younger than 40 years old who are active but not involved in competitive sports.
For the over 40 crowd, hamstring grafts (either autograft or allograft) may work better.
Allografts are preferred for ACL reconstructions that must be revised for any reason as well as for reconstruction of multiple ligamentous damage of the knee.
No matter what type of graft is used, surgeons agree that the results are better when the reconstruction mimics the natural anatomy. The graft tissue is placed inside the knee using tunnels that are predrilled through the bone. Screws hold the graft in place until it is incorporated into the tunnel and healing takes place.
Studies have shown that nonanatomic reconstructions just don't produce the same good-to-excellent results of anatomic techniques. And, it is absolutely necessary to match the length of rehabilitation with the type of graft used for each patient.
For example, allograft tissue takes longer to heal within the bone tunnels. Rehab is extended to allow for that delay. Patients who intend to return-to-play in a competitive or high-intensity sport must also be given additional time to train. And the surgeon and rehab therapist must take into consideration that high-level athletes will put the graft to the test with running, jumping, quick turns, and sudden stops.
Let's back up now and take a look at the specifics of graft selection. It's clear now from several decades of surgical treatment that every patient must be evaluated individually. There is no "one-graft-fits-all" choice for anterior cruciate ligament (ACL) repairs.
First, is the patient male or female? Women are more likely to experience graft failure with hamstring autografts. Next, what sport is involved? Many patients participate in multiple sports year-round. The surgeon must consider each graft type based on the activity and intensity level.
Autografts involve donor site morbidity -- in other words, problems that develop where the tissue was taken from or harvested. Bone-patellar tendon-bone autografts present the greatest donor site problems.
There can be pain when kneeling -- that's the main difficulty after the reconstruction has taken place. Fracture of the patella (kneecap) and loss of knee extension are two other possible complications of autograft BPTB. You can see why this might not be the best choice for someone who isn't fully invested in the rehab program or who has a low threshold for pain tolerance.
But the bone-patellar tendon-bone (BPTB) graft provides a good, stiff ligament needed to maintain knee stability. It is less likely to stretch out and more likely to heal well compared to the hamstring graft. The autograft has a better track record in these two areas compared to a BPTB allograft. These features of the BPTB graft make it a better choice for the active young adult who is eager to get back into strenuous sports activity.
Now what about that hamstring graft choice? We mentioned it is the strongest graft material. There are fewer problems at the donor site. But it takes longer to heal compared with the BPTB graft. Athletes must rehab a full month longer (at least). The rehab program must pay close attention to getting full hamstring strength back. And the risk of graft stretching and losing tension is greater with a hamstring graft.
Studies also show that graft failure is more likely with the hamstring graft. There's more joint laxity (looseness) with this type of graft. Women already have greater knee laxity than men so the hamstring graft may not be ideal for them.
Finally, there's nothing more disappointing than a graft failure in a young athlete eager to get back into action. Allografts seem to have a higher failure rate in this patient population. It is suspected that the reason for this is the sterilization process used to make sure the graft doesn't harbor any infections or other diseases.
In summary, there are risks and benefits with any soft tissue graft. As each patient faces the decision of choosing one over the other, conversation with the surgeon is important. Selecting the graft type is a personal choice based on each patient's needs, activity level, goals, and preferences. The decision will be influenced by surgeon experience and preference as well.
Reference: Matthew R. Poulsen, MD, and Darren L. Johnson, MD. Graft Selection in Anterior Cruciate Ligament Surgery. In Orthopedics. November 2010. Vol. 33.No. 11. Pp. 832-835.