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The Future of ACL Grafts: Is It Here Yet?

Right now the "gold standard" for reconstructive surgery of the anterior cruciate ligament (ACL) is graft replacement of the ruptured tendon. The surgeon uses either a piece of the patient's patellar tendon or hamstrings tendon. Tiny tunnels are drilled through the bone to secure and attach the graft tissue.

But for as many advantages as there are to these graft options, there are just as many disadvantages. The disadvantages are the reason researchers continue to look for other treatment approaches that have fewer limitations and fewer adverse effects. Tissue engineering, the use of growth factors, bone morphogenetic protein (BMP), and other types of cells in ACL reconstructive surgery remain under investigation.

This topic is of interest to both medical and veterinary surgeons as humans and animals experience ACL damage requiring surgery. In this review article from the School of Veterinary Medicine in Shiraz, Iran, veterinarians present an update on graft selection in ACL reconstruction and efforts to improve bone tunnel healing. They discuss past treatment choices, current strategies, and reflect upon future approaches.

The authors provide a nice summary in table form of the advantages and disadvantages of three graft types used in ACL reconstruction (autograft, allograft, artificial or xenograft). After giving an in-depth discussion of each type, they briefly summarize the pros and cons of each one.

For example, patellar tendon grafts are thicker and therefore stronger (biologically and mechanically) compared with hamstring tendon grafts. But the patellar tendon graft leaves a more unsightly and visible scar and they are slower to incorporate into the body and heal. Because the graft tissue is taken from the soft tissues that help extend (straighten) the knee, there can be a negative effect on the knee extensor mechanism.

Patellar tendon grafts harvest easily so the time in surgery is less but the cost is higher compared with hamstring tendon grafts. Potential surgical and post-operative complications include patellar fracture, patellar tendinopathy, knee pain, and patellar crepitus (crunching or clicking of the patella as it moves up and down over the knee).

Hamstring tendon grafts (when taken from the patient) have a higher rate of problems at the donor site. But rehabilitation is less intensive compared with patellar tendon grafts. On the plus side, there are no obvious scars at the donor site making them more pleasing cosmetically. Attaching the graft (called fixation) can be a challenge.

Patients who have hamstring tendon grafts can lose some of the function of the hamstrings. The end-result may be less than a full return to all activities. Graft failure and rupture at the bone tunnel site occurs more often with hamstring tendon grafts. So does degenerative joint disease several years down the road.

Knee joint laxity is reported more often with hamstring tendon grafts compared with patellar tendon grafts. This may be because there is more elasticity in the hamstring tendon compared with the stiffer patellar tendon.

So -- what is the future of ACL reconstruction? Can surgeons find a better way to deal with the limitations by improving the current surgical approaches? Can scientists find alternatives that improve the healing potential, shorten the time in rehabilitation, and yield better results with fewer problems and a lower failure rate?

The answer to the first question is found in the details of this article. Many efforts are being made and reported by surgeons to find solutions by changing and improving surgical technique. The answer to the second question is: not yet. Xenografts (e.g., from calf skin or calf small intestine) are not readily available as yet. Efforts to develop an artificial ligament (also referred to as a ligament-augmentation device) have not been successful as yet. Such a system could help patients heal and rehab faster but may not be as strong or as resilient as natural tissue.

Ahmad Oryan, et al. Graft Selection in ACL Reconstructive Surgery: Past, Present, and Future. In Current Orthopaedic Practice. May/June 2013. Vol. 24. No. 3. Pp. 321-333.


*Disclaimer:* The information contained herein is compiled from a variety of sources. It may not be complete or timely. It does not cover all diseases, physical conditions, ailments or treatments. The information should NOT be used in place of visit with your healthcare provider, nor should you disregard the advice of your health care provider because of any information you read in this topic.
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