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Cartilage is a type of specialized connective tissue. There are three main types of cartilage: hyaline (articular) cartilage, fibrocartilage, and elastic cartilage. Hyaline (articular) cartilage provides a smooth, white, glistening layer covering the femur, tibia, and undersurface of the patella. The main functions of the hyaline cartilage is to provide shock-absorbing properties and allow for a frictionless smooth surface. Articular cartilage lacks blood supply and therefore has a limited capacity for healing. It can be injured by trauma or repetitive injury.
Cartilage injuries may cause pain, swelling, and/or locking if the fragment has separated into the joint. The surgical treatment options for cartilage damage are: debridement (cleanup), microfracture, cartilage (osteochondral) transplant, allograft, and chondrocyte transplantation. These cartilage restoration procedures can be done using minimally invasive arthroscopic techniques.
The microfracture technique is used for full thickness cartilage defects with exposed bone. Articular cartilage has a limited capacity to regenerate itself due to its lack of blood supply. Therefore, the microfracture technique was designed to stimulate a biologic repair for this type of cartilage. A minimally invasive arthroscopic technique is used to place microfracture holes into the exposed bone, which allows the release of blood and bone marrow contents into the cartilage defect. This activates a healing response and stimulates the production of the fibrocartilage layer, which forms over the exposed bone. This technique is very effective for cartilage restoration.
Osteochondral (cartilage) transplantation (OATS) procedures are designed for full thickness chondral defects. Small chondral defects are treated by removing an osteochondral cylinder (plug) from a specific area within the knee joint that does not require cartilage to function properly. This osteochondral cylinder (plug) is then transplanted to the affected area in order to repair the chondral defect.
Large chondral defects can be treated using an allograft (cadaver) osteochondral graft. The typical patient considered for this procedure is a young, active individual with a traumatic isolated chondral injury. The advantage of this procedure is that it allows placement of hyaline (articular) cartilage into the chondral defect. This technique is performed through a minimally invasive arthroscopic procedure, or through an open technique depending on the size and location of the lesion.
Some cartilage lesions are too large for microfracture or autograft OATS to work successfully. Thus, an allograft OATS surgery may be required in some of these cases. In this surgery a cylindrical area of bone is removed where the cartilage lesion is located. A similar sized bone plug with overlying articular cartilage is then removed from a matched cadaver. This cylindrical area of bone is then placed in the defected area in order to repair the cartilage lesion.
Chondrocyte transplantation is used for relatively large cartilage defects in the knee, where the underlying bone is normal. This procedure is usually done in one of two ways. Cartilage cells can be harvested from the patient, sent to a lab, grown, and then later implanted into the patient via a second surgery. The other option is to use fetal chondrocyte cells, which requires only one surgery. In either case the lesion is cleaned of any residual cartilage. A tissue patch is then sewn into the lesion and cartilage cells are injected into the area. These cells then grow into hyaline (articular) cartilage.