Features October 2013 Issue

Regenerating Lost Cartilage

Cartilage restoration may delay the need for joint replacement, but its benefits are limited, a Cleveland Clinic expert cautions.

Joint replacements can work wonders if you have significant cartilage degeneration from arthritis. But if the damage is limited to a small area of your knee or other joints, you may not need such a major operation.

Enter cartilage regeneration.

Several procedures can stimulate the growth of new cartilage, relieve pain and improve joint function. However, questions remain about the durability of this new tissue, a Cleveland Clinic expert says, and although these operations are less taxing than joint replacement, they still require a commitment to rehabilitation.

Marty Bee

In microfracture, tiny holes, or micro­fractures, are made in the bone, allowing bone marrow to seep out and form a blood clot over the defect. Scar tissue, which then forms, acts as replacement cartilage.

“They have very mixed results,” says James Williams, MD, chief of surgery and director of the Cartilage Restoration Center at Cleveland Clinic’s Euclid Hospital. “If you read the literature, there’s about an 80 percent success rate with any of them. They’re still a work in progress. The magic bullet hasn’t been established yet.”

A youthful pursuit
The most common cartilage-repair procedure is microfracture, which entails clearing tissue debris from the joint and creating tiny holes in the subchondral bone underlying the damaged cartilage. Bone marrow then seeps out through these holes, carrying mesenchymal stem cells that mix with the blood clot that forms. This process results in the formation of repair cartilage called “fibrocartilage.”

Dr. Williams says microfracture works best for patients under 30. As patients get past this age, the number of mesenchymal stem cells drops off significantly, adversely affecting the results. Additionally, older patients usually have larger or more extensive areas of injury, with evidence of early osteoarthritis. “And, some microfractures turn from a fibrous cartilage to more of a bony tissue at about the two-year mark,” he adds. “Patients come back with pain at the site two years later, and when we do an MRI there’s a big bony bump there.”

In autologous cartilage implantation (ACI), doctors use an arthroscope to harvest cartilage from part of the knee joint. The tissue is then sent to a laboratory, where cartilage cells are cultured by the millions. In a second operation, the surgeon implants the cells back into the joint and removes a piece of periosteum (the membrane that covers the bone’s outer surface) to seal the cells in place.

Another procedure, osteochondral autografting (mosaicplasty), entails the removal of one or more cylindrical plugs of cartilage and bone from a healthy, non-weight-bearing part of the joint. Those plugs are then transplanted into a damaged area in the knee, ankle or shoulder, like fixing potholes in the cartilage.

Adherence to the postoperative protocols is imperative. Patients undergoing any of these procedures remain on crutches for six weeks or more and use continuous passive motion (CPM) therapy­—in which the joint is gently moved by a machine for six to eight hours a day—to aid in their recovery. With both procedures, the new cartilage is not as durable as your body’s natural hyaline cartilage.

“Cartilage restoration procedures are technically demanding,” Dr. Williams says. “There’s a long recovery with almost all of them. For most of these cartilage techniques, it’s at least six months, and complete strength isn’t regained for almost a full year.”

Another option
Dr. Williams recommends debridement—an arthroscopic removal of debris from the affected joint—coupled with physical therapy and viscosupplementation (injections of hyaluronic acid), as an alternative to cartilage restoration for certain patients with early arthritis.
“The reality is, for most people in the early stages of arthritis with some early degenerative meniscal tears, this is probably the most appropriate treatment,” he says.