Avascular necrosis (AVN) occurs due to the temporary or permanent loss of the blood supply to an area of bone. As a result, the bone tissue dies and the bone collapses. If AVN involves the bones of a joint (e.g.: the talus) it often leads to destruction of cartilage, resulting in arthritis and pain. In the case of the talus, three joints can be affected:
- Ankle joint
- Talonavicular joint (a joint in the middle of the foot)
- Subtalar joint (the joint below the ankle)
The ankle joint allows up and down movement of the foot, while the subtalar and talonavicular joints allow in and out movement of the foot. The normal function of the subtalar joint is to allow walking on uneven surfaces, inclined surfaces, ladders, etc. without falling. AVN can be caused by two large categories:
- Trauma – a fracture (breaking) of the bone disrupts the blood supply to the bone
- Nontraumatic – include idiopathic (no cause is ever found), steroids (e.g.: anabolic and high dose corticosteroids (prednisone) given for such diseases as rheumatoid arthritis, lupus, and cancer), excess alcohol consumption, sickle cell anemia, radiation treatments, and chemotherapy
Symptoms and Diagnostic Process
Once collapse of the talus occurs, then problems begin, including arthritis and deformity. These are very difficult to correct surgically, but with newer reconstructive treatments available, have been very successful.
Diagnosis of avascular necrosis of the talus may involve:
- CT Scan
Treatment options for avascular necrosis of the talus include:
- Ankle Fusion – traditionally, when arthritis of the ankle joint occurs after AVN and talus fracture, a fusion of the ankle may be recommended. This fusion is a complicated operation and the results of the fusion are not always predictable and ankle motion is lost. For this reason, alternative treatments are desirable.
- Core Decompression – a surgical procedure in which a hole is drilled in the talus, which may lead to decompression of the bone and resultant healing of the talus because it increases the blood supply to the talus. It can only be used at the early stages of AVN.