Avascular Necrosis AVN of the Ankle
Anatomy of 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.
What happens when AVN strikes
Avascular necrosis (AVN) is a process that is 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 the destruction of cartilage, resulting in arthritis and pain.
In the case of the talus, 3 joints can be affected; the ankle joint, the talonavicular joint (a joint in the middle of the foot), and the subtalar joint (the joint below the ankle).
AVN in the ankle can be caused by one of two main reasons; trauma and non-traumatic.
In the cases of trauma, a break or fracture disrupts the blood supply to the bone with the result of AVN. For non-traumatic AVN this can be of no known reason, steroid use, etc as described in Causes of Avascular Necrosis AVN.
Avascular necrosis of the ankle can be quite devastating, and lead to a total loss of the ankle joint with arthritis, deformity, and pain. The development of AVN from a break or fracture is determined by the type of fracture. Fractures that are not very severe (they do not shift or displace much), and in these fractures, the incidence of AVN is lower. However, when the talus dislocates out of the ankle socket, the incidence of AVN is very high, almost 100%.
Summary of the available treatments for AVN of the Talus
1. Fusion of the ankle: This treatment glues together the ankle and limits the up and down range of motion permanently. The fusion is not easy to accomplish, and the success rate of this type of surgery can be unpredictable.
2. Total ankle replacement: Total ankle replacement is now an accepted treatment for ankle arthritis, but cannot always be performed if AVN is present. The ankle replacement must have a good bone to sit on, and if the AVN is extensive, it cannot be performed.
3. Drilling of the talus (decompression): There is a lot of evidence that by creating a hole with either a drill or a device that looks a small apple corer to increase the blood supply to the talus. The drilling creates little holes and channels that allow tiny little blood vessels to grow and improve the blood supply to the talus.
4. Muscle flap: All muscle has a blood supply to it in order to stay alive. The procedure moves a small muscle on the side of the outside of the foot into the talus. This is a new procedure, the results seem to be good.
5. Free vascularized bone graft: It is possible to take a tiny blood vessel attached to a piece of bone and using the microscope, to transplant this into the talus.
6. Shock wave (ESWT): This is a nonsurgical method that increases the blood supply to the talus.
7. Total talus replacement: This is a novel technique of replacing the talus with a metal implant.
Acknowledgement Dr Jagadish Devarajan
Also see AVN Treatments