Introduction
An ankle fusion surgery (or arthrodesis) is commonly suggested for a degenerative (worn out, painful) ankle joint. For many years, surgeons have considered an ankle fusion to be the permanent solution for advanced degenerative arthritis of the ankle joint. An ankle fusion is quite durable. After the ankle joint is successfully fused, patients can usually walk with a near normal gait (way of moving) and without the pain of arthritis.
In the majority of cases, surgeons consider the ankle fusion to be the most appropriate treatment for a degenerative ankle in a young patient. This is due to the high demands that an active adult will place on his or her ankle over time. Artificial ankle replacement may not be durable enough in a younger, high demand patient to withstand the stress. Surgeons have thought that the ankle fusion could permanently solve the problems faced by the patient with a degenerative ankle.
However, over the years surgeons have found that by fusing the ankle, additional stress is placed on the other joints of the foot. With a fusion, the ankle joint no longer moves. Therefore, the remaining joints are forced to move more than usual during walking. The added stress can, in time, lead to arthritis of these joints. The result is a painful foot that may require additional surgical procedures to control these new problems.
In the past, the most common solution was to fuse the arthritic foot joints. However the foot is then very stiff, creating an abnormal gait and making walking difficult. Also, the abnormal gait can eventually lead to problems affecting the knee, hip and back.
Today, many surgeons are considering a new technique for degenerative arthritis in the foot joints. Most ankle fusions don’t allow for a conversion to an artificial ankle later in life and is usually considered the final surgery.
However, some leading foot and ankle surgeons, such as Dr. Stephen F. Conti at the University of Pittsburgh, are now suggesting that the ankle fusion be performed from the outset with the idea of returning many years later to convert it to an ankle replacement. Dr. Conti’s procedure makes it easier to convert the ankle fusion to an artificial ankle later.
The Surgery
The surgeon must consider several factors during this type of fusion surgery.
First, the surgeon will need to consider the incision site. Incisions on the front, sides, and even the back of the ankle have all been used successfully in fusion surgeries. However, since the artificial ankle is inserted through an incision on the front of the ankle, the doctor should use this approach with the initial fusion. Incisions that are too close together around the ankle can cause damage to the blood supply to the skin, even years later. Using the same incision reduces the risk of skin and incision healing problems during the artificial ankle replacement surgery.
Second, the medial and lateral malleoli (two bony bumps on each side of the ankle) must not be removed. In the past doctors routinely removed portions of the malleoli in order to improve the appearance of the fused ankle. The malleoli are not necessarily important to the success of the ankle fusion, but they are very important when considering the artificial ankle replacement. These two structures are used to hold the socket portion of the artificial joint in place. The fusion surgeon must keep this in mind and perform the operation in such a way that the two malleoli are not completely removed and enough bone remains to hold the artificial joint in place.
To accomplish this the same instruments and guides utilized during ankle replacement surgery can be used during fusion surgery as well. The amount of bone that is removed during the ankle fusion should be the same, or less, than the amount of bone removed during the artificial ankle replacement. This guarantees that there will be enough bone to hold the artificial ankle joint firmly in place. Cuts to the bone are made at the right angles and depths to allow the artificial ankle to be inserted later.
In some cases, surgeons try to fuse the fibula to the tibia during the ankle fusion. This is routinely done during the ankle replacement surgery so that the bone that holds the socket is stable. Doing this during ankle fusion allows the fibula and tibia heal together before ankle replacement surgery is done. According to Dr. Conti this may make the ankle replacement more stable immediately after the surgery.
Conclusion
The number of ankle fusions that could benefit from conversion to an artificial ankle joint is not known. Fusions can provide a lifetime of good, painless function. But for some patients who could develop other problems with the joints of the foot, it may be wise to plan ahead. When faced with the need for an ankle fusion, surgeons, as well as patients, might find it beneficial to leave the option open for an artificial ankle.
