New Surgery Improves Outcomes for Severe Flat Foot Deformity

A surgery developed at Hospital for Special Surgery can improve patient outcomes in individuals with severe adult flat foot deformity, a problem that is increasingly being seen in hospitals across the country. Patients who undergo the new surgery have better long-term outcome and mobility than those who undergo traditional surgery. The paper will be presented at the annual meeting of the American Orthopaedic Foot and Ankle Society (AOFAS, abstract 348) in National Harbor, Md., on July 8.

“Before this study, we were not sure whether you could salvage patients with flat foot and ankle deformity and correct their ankle as well as their foot deformity,” said Jonathan Deland, M.D., chief of the Department of Foot and Ankle Surgery at Hospital for Special Surgery (HSS). “Now we know that with this technique you can save the ankle, and it provides a correction of the deformity even at nine years after surgery.” Dr. Deland developed the surgery and is senior author of the study.

Adult acquired flat foot deformity is basically a severe type of flat foot that develops for unknown reasons in individuals who have had flat feet all their life.

It is more prevalent in women and those who are overweight, and it usually develops in individuals in their 40s and 50s. In stage I of the deformity, the tendon that runs along the inside of the ankle begins to degenerate. In stage II, the arch starts to fail, and a person develops a more severe case of flat foot. As the arch continues to collapse and the flat foot becomes more pronounced, mobility becomes difficult, and the foot becomes stiff, which is considered stage III.

In the most severe stage, stage IV, the ankle starts tilting and is at risk of developing arthritis as a result of the deformity. “These people have tremendous flat foot to the point that their ankle is involved,” said Scott Ellis, M.D., foot and ankle orthopedic surgeon at HSS and first author of the study. In these people, the extreme flat foot has injured the deltoid ligament, a strong, flat triangular ligament that is located on the inside of the ankle that provides support to prevent the ankle from over pronating. In stage IV, the deltoid ligament has become stretched and incompetent, which is what allows the ankle to tilt.

If the ankle deformity is severe and symptomatic enough, then surgeons either perform an ankle replacement, which is very difficult, or, more commonly, fuse the ankle. “The fusion is not ideal because it takes all the motion away in the ankle in a patient who already has a foot problem,” Dr. Ellis said. “Imagine walking without motion in your ankle. It changes your gait and it leads to arthritis in the other joints of the foot over time, eight to 10 years down the line, because you start having to use those joints to take up the slack of motion that is not occurring in the ankle.”

In the new surgery for stage IV deformity developed at HSS, surgeons not only reconstruct the flat foot deformity, but they also reconstruct the deltoid ligament using a tendon that runs along the outside of the calf called the peroneus longus. A person can function without their peroneus longus. Alternatively, the peroneus longus can be kept and a cadaver tendon used.