Dr. Warren R. Dunn
Young, active patients with disabling cartilage damage in a knee have a host of treatment options in Middle Tennessee today, giving them hope to delay a joint or partial-joint knee replacement until they are much older.
Under the umbrella term “cartilage restoration” is a list of several procedures designed to repair or replace deteriorated cartilage, and several area surgeons offer these options designed to eventually return patients to their active lifestyles.
The Vanderbilt Center for Cartilage Repair and Osteochondritis Dissecans (OCD) Treatment is one of the few clinics like it in the country. The center is dedicated, of course, to cartilage repair, but also to treatment of OCD — a rare condition, usually of the knee, in which the bone that supports the cartilage softens, causing separation of bone and cartilage with resulting pain, swelling and mechanical problems.
Warren R. Dunn, MD, co-director of the center, said one of the first options for cartilage restoration, and one of the simplest, is called a microfracture procedure. “If it’s a smaller defect we call ‘contained,’ meaning it has a good border or normal cartilage around it, we often start with a microfracture procedure,” he said. The surgeon cleans up loose cartilage around the defect and drills small holes in the bone to reach deeper, more vascular bone and encourage it to bleed. The idea is that those cells from the deeper bone rising to the surface might stimulate cartilage growth.
Then there are other options, involving various degrees of cartilage transplantation:
- Autologous chondrocyte implantation (ACI),
- Osteochondral autograft transfer (OAT) and
- Osteochondral allograft transplantation and meniscal transplantation.
ACI is growing in popularity in Middle Tennessee, according to Michael R. Jordan, MD, a Murfreesboro-based surgeon with Tennessee Orthopaedic Alliance and Middle Tennessee Medical Center. During ACI surgery, a cartilage defect is filled with millions of cells grown in a laboratory from a small piece of the patient’s own cartilage.
Jordan said the procedure requires sewing a membrane over the top of the cartilage, “thereby putting a manhole cover over the hole, using a glue to seal it. Then you squirt the cartilage cells underneath that. Then they percolate and grow for a long period of time. It takes about six months for all of that to happen.”
In fact, ACI is not for the impatient patient, as it may be a year before the repairs reach their maximum potential. Patients immediately begin physical therapy. “Knee movement is good and enhances cartilage growth, but impact weight-bearing is not. You spend a long time on crutches letting it heal,” Jordan said.
Jordan noted that his practice sends patients’ cartilage cells for growth to a Boston-based biotechnology laboratory called Genzyme.
Other countries are using matrix and scaffold implants that are much-improved alternatives to the membrane used in the United States in ACI procedures. “The cartilage cells get impregnated into these scaffolds, and you can put those into the defect and don’t have to harvest the periosteum and sew the flap over the defects,” Dunn explained. In fact, the scaffold has the consistency of chewing gum and is easily placed. Those options haven’t yet received FDA approval here.
Jordan noted that researchers are also working on arthroscopic implantation of those cartilage cells rather than having to open the knee up and sew the “manhole cover” in place. Other researchers are working on arthroscopic delivery of cartilages bound together by glue, he added.
This procedure involves harvesting plugs of cartilage and bone from a part of the knee not as crucial to weight-bearing and moving those plugs to a defect in a more critical area. Dunn said this technique is also known as mosaicplasty because of the mosaic-like appearance of the plugs’ placements. This technique is performed arthroscopically.
Using Donor Cartilage
Dunn called using cadaver plugs “a last resort,” but for many patients, it’s just what the doctor ordered. Both osteochondral allograft transplantation and meniscal transplantation require cadaver cartilage and/or bone to fill a large knee defect.
Jordan said using donor material actually has some benefits over ACI or OAT. “Transferring the donor cartilage heals faster, and the surgery is easier to get over because it’s already cartilage and has a bone platform underneath it. But then there’s the downside, even though it’s a small risk, of disease transmission,” he said.
No matter which cartilage-restoration procedure is deemed best, they all are designed with younger, active patients in mind. “The best candidates are people who are 15 to 50 who have a very focal defect. They’re missing an area of cartilage,” Jordan said. “People who are candidates for knee replacements or partial-knee replacements are not good candidates for cartilage transplants.” Patients with arthritis are suffering “global loss,” Dunn said, which makes cartilage transplantation ineffective.
However, one of the biggest hurdles for cartilage transplantation may be the cost. Jordan said third-party payers “require significant documentation, and it’s often denied the first time around. And there are some insurance companies that just have a flat ‘we’re-not-paying-for-it’ policy.” The cartilage harvesting or growing costs about $10,000, followed by the cost of surgery and significant rehabilitation. “So they are very expensive procedures,” he said.