Knee Cartilage Transplant
New Advances in Knee Cartilage Transplant: Cartiform and DeNovo NT
It’s safe to say that most people never give a thought to their knee cartilage — which does much of the work of the knee joint — until something goes wrong and normal activities are painful or impossible. But for those who don’t yet need or desire artificial knee joint replacement, the University of Maryland offers several versions of cartilage transplant therapy — including a brand-new procedure called Cartiform — that can help these individuals move as they once did and regain their previous lifestyle.
The human body’s own intact cartilage is still the optimal material for lining knee joints, but car accidents, falls, and sports- and work-related injuries can destroy some or most of the articular cartilage in knees. To replace this missing or damaged material, cartilage transplants using either patient or cadaver cells can be the next best thing.
“Commonly these patients have been told they don’t have options, that they’ll eventually need a knee replacement and will just have to deal with the pain until they’re older,” says R. Frank Henn, M.D., an assistant professor of orthopaedics at the University of Maryland School of Medicine and a team physician for the University of Maryland Terrapins. “When they get to me they’re disheartened and then encouraged simply because we have options for them. I have to prep their expectations for the road to recovery — it’s usually a year before they get back to athletic-type activities — but when they get back to that, they’re a different person and their family gets their loved one back.”
Carticel: The Gold Standard procedure
In use for more than 20 years, autologous chondrocyte implantation (ACI) remains the gold standard of knee cartilage transplant procedure. The two-stage therapy involves arthroscopically removing a small piece of normal cartilage tissue from a lesser load-bearing area of the joint and growing those cells in vitro over six to eight weeks from a few hundred thousand to 30 to 40 million. The treatment, known by the trade name Carticel, later re-implants the cells under a patch, where they grow to fill the “pothole” defect in the cartilage, Dr. Henn explains.
“The advantage is that it’s autologous tissue,” he says. “It takes time to grow — about 12 to 18 months — to get back to the point where it has an impact on the patient’s activities. But it’s appealing to use the patient’s own cells to do that. All other transplants use donor tissue.”
Donor Tissue "Immunoprivileged"
While the remaining options to transplant knee cartilage all involve donor cells, a huge benefit is that such tissue is “immunoprivileged” with no lymphatic or blood vessels, so it’s isolated from the immune system and unable to cause rejection, Dr. Henn says. These cartilage replacement procedures use cadaver tissue — as is the case with many organ and tissue transplants — but immunosuppressive drugs are typically required to prevent rejection in other types of transplants.
“We’re always concerned about disease transmission with donor cells, but fortunately it’s more theoretical now and donors are tested first,” Dr. Henn says.
One well-established donor transplant option is known as a fresh osteochondral graft, in which both bone and cartilage are transplanted. Optimal patients for this procedure have more extensive bone and cartilage damage, and the donor bone melds into the “host” bone after this single-stage surgery.
“There’s no initial procedure needed to harvest tissue from cartilage,” Dr. Henn says. “And it’s cheaper than ACI from a societal standpoint. But one of the downsides is that graft availability is limited. We need healthy, normal cartilage, and donors have to be young and healthy. We have to wait for donors to become available for many of these patients.”
Knee cartilage transplantation advances
Two new advances in knee cartilage transplantation involve the transfer of only cadaver cartilage tissue. The first, which has been available for the last several years, is called DeNovo NT and uses live juvenile donor cartilage that is cut into small pieces and implanted into the defect in the patient’s cartilage with a fibrin glue that seals the cartilage in place. Because juvenile cartilage is obtained from young donors, the cells are numerous and have great healing potential, Dr. Henn says.
Only recently available, the newest knee cartilage transplant option is known as Cartiform and originates from Osiris Therapeutics in Columbia, Md. Instead of trimming cartilage into small pieces and waiting for it to grow, Cartiform uses mature cartilage and pokes tiny holes throughout, like a mesh, that allow the host tissue to grow into it, Dr. Henn says. Like DeNovo NT, it is also affixed to the patient’s bone and cartilage using a fibrin glue.
“This product and approach holds a lot of promise,” he says. “It seems to solve the problem of getting mature cartilage tissue alone to heal to the bone.”
To refer a patient for consultation, please call 1-800-373-4111. For an urgent transfer, please call University of Maryland ExpressCare at 410-328-1234.