Joint preservation techniques are used in patients with cartilage defects to preserve the joints and to restore the function.
Articular cartilage is the cartilage that covers the bony surface of joints. It has a smooth surface which allows the bones of the knee joint to slide over each other with very little friction. Articular cartilage is often damaged by injury or normal wear and tear. Articular cartilage, when damaged or worn away, the affected joint becomes painful, stiff, and has limited range of motion. As the articular cartilage has limited ability to heal by itself, surgical repair may be required to stimulate the growth of new cartilage. Articular cartilage restoration relieves pain, improve function and can delay or prevent the onset of arthritis in the joint.
Cartilage restoration can be achieved using different techniques.
- Microfracture surgery: Microfracture surgery is appropriate for patients having single lesion and healthy subchondral bone. Microfracture can be done using an arthroscope a long, thin device with a tiny camera attached at the end to see inside your knee. Your surgeon uses a small pointed tool called an awl to make very small holes, microfracture, in the bone underlying the cartilage called subchondral bone. This stimulates the healing process by increasing the blood flow to the surface which brings in new cells that build new cartilage.
- Drilling: This technique involves use of a surgical drill or a fine wire to make multiple small holes through the damaged area to penetrate the subchondral bone. This generates a healing response within the defect.
- Autologous chondrocyte implantation: Autologous chondrocyte implantation (ACI) is a two-step procedure; first step is an arthroscopic surgery to remove the tissue containing healthy cartilage cells from an area of the bone that does not carry weight. These cells are cultured and multiplied in laboratory over a 3- to 5- week period. In second step, the newly grown cells are implanted through an open surgical procedure, or arthrotomy. During this surgery, a periosteum, layer of bone-lining tissue is sewn over the area of damaged cartilage. Once the area is sealed with fibrin glue the cultured cartilage cells are injected underneath the periosteal cover.
This procedure is appropriate for patients with single lesion of large area. As the patient’s own cells are used chances of rejection is not a concern. However, it is a two-step procedure, requiring large incision and lengthy recovery.
- Osteochondral autograft transplantation: In this procedure, healthy cartilage (graft) taken from a non-weight-bearing area is transferred to a damaged area of the knee. The graft is taken as a cylindrical plug of cartilage and underlying bone. Then the graft is matched with damaged area and transplanted into place. This leaves a smooth cartilage surface in the joint. Transplantation may be performed using a single plug or by mosaicplasty where multiple plugs are used.
This technique is used for patients with small areas of cartilage damage because of the limited availability of the healthy cartilage from the same joint.
- Osteochondral allograft transplantation: During this technique tissue graft taken from a cadaver donor, known as allograft is used to repair the damaged cartilage. Allograft may be used if the cartilage defect is too large for an autograft