What is an osteochondral defect of the talus?
An osteochondral defect is an injury of the joint surface. It is a somewhat rare problem in the talar surface of the ankle. The cause of this problem is far from completely understood and there are probably multiple causes. Trauma can chip the surface of the joint, as the ankle is almost dislocated during a severe ankle sprain. Even when the joint surface is only bruised, the healing can result in a painful cyst that weakens the joint surface. Finally, vascular injuries and natural clots can cut off the blood supply to the joint and allow it to fragment.
Osteochondral defects come in many grades and sizes and this directs the treatment. Often when examining the joint, the surface may appear normal and only when feeling the surface is softening appreciated. At other times, the fragments can be large and separated from the remainder of the joint. Still other times, the defect may contain only residual scar and fragmented cartilage.
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How are they treated?
Treatment of fresh traumatic non-displaced osteochondral injuries is initially through immobilization and weight restriction. Chronic osteochondral injuries can be initially treated through physical therapy, analgesics such as Motrin, and occasionally through intra-articular injection. However, this treatment is often unsatisfactory.
Surgical treatment of these injuries is a balance between the severity of the reconstruction and reconstitution of joint. None of the techniques leaves the joint completely normal. When the fragment is large, the joint can be opened, replaced, and stabilized. If the lesion is small, the fragment can be removed. The defect left is cleaned back to viable bone and allowed to fill with blood clot. The blood clot can regenerate into fibrocartilage, an immature disorganized form of cartilage that often decreases pain but is not as resilient as normal articular cartilage.
More complete reconstruction of the articular cartilage is necessary in large defects or in situations where the techniques above are unsuccessful. This is done through an open surgical procedure. In order to gain access to the defect, a cut in the tibia or fibula bone is often necessary. One technique involves harvesting a portion of the knee articular cartilage and bone and replacing the damaged portion of the talar joint with it. Recovery after this procedure is often prolonged and weight bearing must be delayed until the peg and bony cuts heal. Results following this procedure are good in 80-90%. Some private insurances fail to cover this procedure, citing it as investigational. However, because the injuries are relative rare and variable in size and severity, it is unlikely that a large randomized trial will ever be possible.
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