A tarsal coalition is a condition where one or more of the bones of the hindfoot (talus, calcaneus, and navicular) do not fully separate during development. These bones normally split apart (forming a joint) in the early part of pregnancy when the embryo is developing. The coalition holding the bones together can range from flexible fibrous tissue, cartilage, or a rigid bridge of solid bone. The effect of a tarsal coalition is that the position of the hindfoot tends to be fixed in patients with a tarsal coalition. Sometimes the foot is fixed in a neutral position but sometimes it is fixed in a fairly flatfooted position. In either case the hindfoot does not move normally.
The most common tarsal coalitions are:
Many tarsal coalitions are asymptomatic and people may live their whole life without realizing that they have a tarsal coalition. However, certain tarsal coalitions can create symptoms which in some individuals can be quite significant. The main symptoms are:
Often a tarsal coalition can be diagnosed on a plain x-ray of the ankle or the foot. There are certain plain x-ray signs that are classic for certain tarsal coalition including:
However, in many instances a tarsal coalition will not be seen on a regular x-ray and a CT scan or MRI will be needed to establish the diagnosis. CT scan can best determine the extent of bone bridging in larger coalitions, but MRI is best for smaller, non-bony coalition lesions
A variety of non-operative treatments may be helpful in managing the symptoms of a patient with a symptomatic tarsal coalition. These include:
In some instances surgical intervention is warranted. This is the case when symptoms become too severe despite adequate non-surgical management or if either because the symptoms have become too severe or there is a: