Cartilage injuries to the knee are some of the most difficult injuries to treat; once damaged, articular cartilage has only a limited ability to repair itself, and treatment options available are not always successful. However, a new transplant technique has shown great promise in treating these serious injuries. Known as Autologous Chondrocyte Implantation (ACI), only a handful of select physicians and hospitals perform this innovative and highly specialized surgery. Dr. Kenneth Zaslav, Chief of Sports-medicine at the Advanced Orthopedic Centers in Richmond Virginia, recently spoke about his experiences with the implantation technique.
"This procedure shows the promising possibility for long-term success", Dr. Zaslav commented. "The follow-up evaluations demonstrate that the implanted cartilage is performing very well. The real test is how these treatments hold-up over the long-term, and the transplant procedure is demonstrating a real ability to withstand normal use." Dr. Zaslav's center was recently the first site approved in a new multi-center FDA sanctioned study on the use of ACI in the treatment of patients who have failed other cartilage treatment procedures.
Autologous chondrocyte implantation (ACI) is a technically demanding procedure, with fewer than 500 performed last year, however, over 6,000 have been performed worldwide since itís commercial launch in 1995. Initial studies suggest that the procedure is generally providing a robust and durable supplement to patients' own remaining cartilage, having a success rate between 75% & 80%. After performing the procedure for the past four years and having completed 36 procedures, Dr. Zaslav has been impressed with its early results.
Building on research from cartilage re-growth studies and implantation procedures, ACI was first developed in Sweden, by Dr. Lars Petersen in 1987. The procedure actually requires two surgeries, one to remove a sample of the patients own cartilage cells (autologous), the other to implant the newly grown cartilage cells. Retrieving a tiny sample of cells allows a specialized processing facility at Genzyme Biosurgery to grow additional cartilage in a culture that is then implanted 4-6 weeks after the initial operation.
During the implantation procedure, a small piece of periosteum (the thin tissue which covers the bone) is removed from above the patient's tibia (shinbone). While the surgeon works within the knee joint, this tissue is sutured over the cartilage defect to provide a protective cover once the re-grown cells have been implanted. The cultured cartilage cells are injected under the skin-like covering and into the defect where they will continue to multiply and produce a durable repair tissue.
When considering implanted cartilage as a long-term treatment, the ACI treatment appears to have great potential. "Though long term effects of this procedure are still being evaluated, when patients who have had the implants have been examined after a few years, the new cartilage appears similar to normal cartilage tissue," said Dr. Zaslav.
Damage to the articular cartilage of the knee joint is often very debilitating, and few treatments are available after injury to restore the normal functioning of the knee. One technique, chondroplasty, involves shaving the margins of the damaged cartilage to reform and smooth the working surfaces of the joint. More recently, micro-fracture chondroplasty techniques have also been utilized to bring in blood supply from the bone below the cartilage to form a cartilage-like substance at the area of damage. Often, the symptoms of a cartilage injury, such as, pain, swelling, instability, and 'locking' or 'catching' recur within a few years.
Initial studies of ACI recipients have demonstrated strong results; the implant technique is the first treatment to regenerate hyaline like cartilage that might stand up to stress over a long period of time. Damage to articular cartilage is a common problem affecting the joints of millions of people. Considering the poor regenerative capacity of adult articular cartilage and the disability and pain that accompanies these injuries, cartilage damage is a major area of research in the orthopeadic specialty. More than 500,000 arthroplastic procedures and total joint replacements are performed each year in the United States, including about 95,000 total knee replacements and 41,000 other procedures to repair deficiencies of the knee.
Treatment of cartilage injuries of the knee at an early stage can prevent the development of osteoarthritis, greatly delaying or eliminating further treatments, such as a total joint replacement. The best candidates for the ACI procedure are patients under age 50 with stable knee joints that are free of generalized degenerative disease, such as arthritis. The benefits for use in injured joints other than the knee have not yet been evaluated.