Our twin boys both have a condition called calcaneonavicular coalition. Since they are mirror twins, one has this problem on the left foot, the other has it on the right foot. Only one twin is really bothered by the condition — and that’s probably because he is more active in sports activities. If we have surgery done on the twin with the painful foot, should we have the same surgery done on the other child (even though he doesn’t seem bothered by the problem)?

This is a difficult question to answer. An orthopedic evaluation is necessary to see the extent of the problem and evaluate the implications of the condition. Some people with this bony anomaly who never have surgery to correct it, end up developing joint problems and arthritis years later.

Calcaneonavicular coalition refers to the fusing of two bones in the foot: the calcaneus (heel bone) and the navicular bone. A bridge of fibrous cartilage connects the two bones together. The navicular is an important bone because it joins with many other bones in the foot and ankle. It is located on the medial side of the foot (side closest to the other foot). It articulates (moves against) the four and sometimes five other ankle bones.

When calcaneonavicular coalition occurs, the affected individual (usually a child around age 12) reports ankle pain with loss of motion. They are no longer able to point the foot down all the way. Turning the foot and ankle inward can also be limited. The loss of these motions makes it difficult to walk, run, and participate in daily activities at school.

Your surgeon may advise careful watching of the twin without painful symptoms. Follow-up visits every six months may help show any changes that might be occurring. Changes on X-ray or increase symptoms may be signals that it’s time to act.

Surgery to remove the fibrous/bony bridge is the current standard of care. In the past, casting the foot and ankle to immobilize it didn’t help and even made things worse for some patients. Different ways of accomplishing the surgery are being explored.

Usually, a muscle and its attached tendon (the extensor digitorum brevis) are harvested and used to fill the hole left by the surgical removal of the coalition (connecting bridge of fibrous bone). A newer technique using a fat graft is under investigation. Fat might work better because it fills the hole completely where the tendon might not be long enough to do so. Fat also has an ability to be shaped to fit the hole exactly. No unsightly deformity or bony bump is left behind to embarrass the child or rub against shoes.