Richard A. Zell, M.D.
Cartilage is the smooth, gliding surface that lines each of our joints. This tissue allows joints to move freely and gives us our ability to walk, run, jump and play sports. There are many orthopaedic conditions that are caused by damage to the cartilage. The most common disorder is arthritis in which there is a global loss of cartilage. The cause of arthritis is typically hereditary but can also be secondary to inflammatory conditions (such as Rheumatoid Arthritis or gout) or trauma. There are also conditions in which a small amount of cartilage (sometimes with a segment of underlying bone) in a joint is damaged. This can occur after an ankle or knee injury, and are common problems in young and middle-aged athletes. The condition has been called an osteochondral lesion or osteochondritis dissecans when it occurs in the knee and osteochondral lesion of the Talus (OLT) when it occurs in the ankle. The injury is usually located in the lower bone of the ankle joint or the talus.
An OLT usually occurs after an ankle injury such as a sprain or fracture. During these injuries, the lining cartilage of the joint is bruised or sheared off during the twisting injury. Patients will complain of ankle pain, stiffness, swelling and possibly feelings of “catching” in their ankle. Physical examination demonstrates pain with motion of the ankle, swelling, and at times, instability of the ankle. X-rays are obtained to make sure patients do not have fractures or arthritis of the ankle. Occasionally, a small avulsion of bone that the cartilage is attached to, can be seen on the radiographs. An MRI is the best test to reveal an OLT and is helpful for making sure that there are not other causes for the patients pain (such as tendonitis, stress fractures etc.).
A cartilage injury does not necessarily mean surgery. Previous studies have shown that approximately 45% of patients can actually avoid surgery (Tol et al, 2000). Non-surgical treatment includes immobilization in a walking boot/cast, physical therapy, and NSAIDs. If patients have symptoms for more than 6 weeks to 3 months, surgery is recommended.
Even with all of the advances in medicine over the years, there is no perfect treatment for cartilage defects. We do not have the ability to fabricate cartilage that has the same make-up and structure of native cartilage. There are different surgical options available however, for cartilage defects that have been shown to recreate tissue that is close in form/structure to native cartilage and will allow patients to be pain free and return to sports. These procedures include: microfracture, mosaicplasty, allograft reconstruction, autologous cartilage transplantation, and juvenile cartilage transplantation.
The traditional treatment for cartilage injury or defects is microfracture. This is a procedure that can be done using the arthroscope and small incisions. An incision is made so that a small camera may be placed into the ankle joint. A second incision is then made for placement of instruments to allow removal of all loose cartilage in the area of the cartilage defect. Once all loose cartilage is removed, there will be an area of exposed bone. Multiple perforations or drill holes are then made in the bone to allow bleeding and ultimate formation of fibrocartilage or scar cartilage. This tissue fills in the gap with time. The tissue is not as resilient as our normal cartilage but seems to work well. Patients are allowed to move their ankle shortly after surgery but are kept non weight bearing for a few weeks. Return to sports occurs approximately 3 months following surgery. This technique has been found to be best for smaller cartilage defects (less than 1.5 cm in diameter) and is helpful in approximately 79-90% of patients (Ferkel, 2008).
There are certain cartilage defects in the talus that are larger in size. There are also some patients who have undergone a mircrofracture procedure and still having pain or feelings of catching. These patients can undergo a larger procedure called a mosaciplasty. This surgery involves taking a plug of cartilage and bone from another area of the body and placing it in the area of the cartilage defect. Most often the cartilage and bone plug is taken from the knee (in an area of the joint that can function well without cartilage). Using special instruments, the cylindrical plug is then placed into the talus which brings healthy bone and cartilage to resurface the joint. This is a larger procedure that often requires larger incisions and, at times, an osteotomy (cutting the bone of the tibia) to allow placement of the cartilage plug. Mosaicplasty has good results in approximately 90% of patients (Imhoff, 2011) and is best for patients with moderate size defects of the talus cartilage.
There are certain patients who have an OLT in which a large percentage of the talus cartilage is damaged. These patients are often managed with use of an allograft talus. In this procedure, an allograft talus, which is a talus that comes from a person who has passed away and has donated their organs/bones to help others, is obtained from a tissue bank. Prior to sending the allograft talus to the operating room, the tissue is tested for disease to ensure that the tissue/bone is safe for use. During the surgery, special instruments are used to take part of the allograft talus and secure it to the patient’s own talus to resurface the joint surface. This is not a common surgery but can work well for patients with large to massive defects of the talus.
Some novel techniques exist that can be used for talar cartilage defects. One technique is autologous cartilage transplantation. With this procedure, a piece of cartilage is taken from the ankle during an arthroscopy and sent to a company called Genzyme. The company will then harvest the chondrocytes (cartilage cells) from the sample and will grow approximately 12 million new cartilage cells. These cells are sent back to the OR in liquid form. Patients undergo a second surgery in which the grown cartilage cells are placed in the defect and covered with a patch. With time, the implanted cartilage cells allow new cartilage to grow and fill in the defect. This procedure has been done for the past 15 years and is helpful for larger defects of the talus.
Recently, another company has used juvenile cartilage from young donors for cartilage defects. The cartilage is taken from young people who have passed away and whose family has consented to have their tissue donated. This tissue is tested to make sure there is no contamination or disease and then packaged for use in the OR. At the time of surgery, the juvenile cartilage is placed into the cartilage defect and secured with fibrin glue. As time goes by, the cells in the donated cartilage fill in the gap. It is felt that the young age of the donated tissue allows a more robust filling in and repair of the cartilage defect. Studies are underway to see if this treatment will be more helpful than previous techniques for cartilage defects.
Treatment of cartilage defects continue to be an evolving area of study in orthopaedics. This paper concentrated on cartilage defects in the ankle, however the same techniques are used for cartilage defects in the knee and other joints.