Cartilage Repair and Transplantation
Articular Cartilage is the white tissue lining the end of bones where these bones connect to form joints. Cartilage acts as a cushioning material and forms the smooth articulation of bones during movement. An injury to the joint may damage this cartilage which cannot fully repair on its own. Cartilage can degenerate with increasing age, wear and tear, or trauma. Damaged cartilage cannot cushion the joints during movement and the joints may rub over each other causing pain and inflammation.
Cartilage repair describes surgical procedures where orthopaedic surgeons stimulate the growth of new cartilage that restores more normal function. Degenerate conditions can be delayed or potentially prevented with this type of procedure.
Measures employed for cartilage restoration include dietary supplements, microfracture, drilling, abrasion arthroplasty, osteochondral autograft, and allograft transplantation.
Dietary supplements: Dietary supplements such as glucosamine and chondroitin are the non-surgical treatment options for cartilage restoration which are used by some patients with good effect. Chrondroitin sulphate and glucosamine are naturally occurring substances that are present within cartilage. Chrondroitin sulphate and glucosamine obtained from animal sources are available as ‘over the counter’ products and are recommended by some for cartilage restoration. Apart from these, various other nutritional supplements are also recommended such as cod liver oil, calcium with magnesium and vitamin D as a combination, S-Adenosyl-Methionine and Methylsulfonylmethane. The evidence for these supplements is mixed.
Microfracture: In this method, numerous holes are created in the injured joint surface using a sharp tool. This procedure stimulates a healing response by creating an injury designed to generate bleeding, healing and a layer of fibrocartilage.
Sub-chondral Drilling: In this method a drilling instrument is used to create holes in the injured joint surface. Drilling holes stimulates a healing response and growth of a new cartilaginous covering. This method is similar to microfracture.
Abrasion chondroplasty: A high speed shaver is used to remove the damaged, unstable cartilage. This procedure is performed using an arthroscope with a ‘key-hole’ procedure.
Osteochondral Autograft Transplantation: Healthy cartilage tissue (graft) is taken from an area of the joint that bears less weight and is transferred to the site of cartilage loss. This method is used for smaller cartilage defects. Osteo-articular transfer system (OATS) is a surgical procedure to treat isolated cartilage defects which are limited usually 10 to 20mm in size. The procedure involves transfer of cartilage plugs taken from the non-weight bearing areas of the joint which are then transferred into the damaged areas of the joint. This procedure is not indicated for wide spread damage of cartilage as seen in osteoarthritis.
The procedure is usually performed using ‘key hole surgery’ (arthroscopy). The area of damaged cartilage is prepared using a coring tool which makes a perfectly round hole in the bone in the area of damage. The hole is drilled to a size that fits the harvested plug. Next the plug of normal cartilage/bone is then implanted into the hole that was created in the damaged area. The size of the plug used should be slightly larger than the hole so that it has good ‘press-fit’ in the new location. This procedure allows the newly implanted bone and cartilage to replace the defected area.
Possible complications of OATS include donor site morbidity causing pain, avascular necrosis, and fracture. Other complications such as haemarthrosis, effusion (swelling) and pain may also occur. Following OATS procedures, protected weightbearing rehabilitation is recommended with use of crutches and bracing to limit the range of motion.
Osteochondral Allograft Transplantation: A bone/cartilage tissue graft is taken from a human donor and transplanted to the site of the injury. An allograft technique might be recommended if a more significant portion of the joint is damaged.
Autologous Chondrocyte implantation: In this method, healthy cartilage cells are removed using an arthroscopic technique and are cultured in a laboratory. Cultured cells can then be implanted in the damaged area with an open surgical technique involving a second surgical procedure.