A tarsal coalition exists when an abnormal bar or bridge of tissue forms between two bones that are typically separate from each other. This bridging causes restricted motion or lack of motion between the two bones of the foot. The actual definition of coalition “means coming together of two or more entities forming one mass.” The cause of tarsal coalitions is unclear. Many researchers suggest that coalitions are either genetic (congenital) or acquired after birth. The coalition can be boney, fibrous, or made of cartilage.
A congenital coalition is more frequently seen. Research suggests that a congenital coalition is formed from an accessory (extra) bone’s incorporation into the normal foot bone on either side of a joint. There are also thoughts that a coalition results from the failure of cells to separate during development. This is often associated with an inheritable trait. An acquired tarsal coalition may result from arthritis, trauma, tumor or infection. This if often less common in pediatric or adolescent patients. This type of coalition is seen with a decrease in motion and is often associated with a special type of flatfoot deformity which causes even more problems in the individual.
There are three main types of coalitions. These types are based on the tissue type and include: 1. Synostosis (bone union), 2. Synchondrosis (cartilage union), 3. Syndesmosis (fibrous union). When dealing with a synostosis, a complete coalition is seen with all motion nearly absent. Clinically, a tarsal coalition may be found without the patient having symptoms, and is an incidental finding on x-rays. Three main clinical findings are noted: pain, limitation of motion, and muscle spasm. Pain is the most common finding and is usually a deep, aching pain where the coalition is located. This pain is often aggravated by activity.
Tarsal coalitions can be diagnosed in many ways. Clinically, a doctor will notice decreased motion and pain in the area of the coalition. Radiographs (x-rays) are used most commonly used to confirm the diagnosis of a coalition. Sometimes, however, if the coalition is more fibrous or made of cartilage a CT scan or MRI is needed to identify the bar.
There are various ways to treat a tarsal coalition. Not all coalitions cause symptoms and can often be left untreated. The first line of treatment is conservative. This can include restricting motion around the joint that the coalition is occurring with shoe modifications, padding, orthotics, bracing techniques or fiberglass casting. Other options include physical therapy and anti-inflammatory medication as needed to alleviate the pain.
Surgically, many factors must be looked at beforehand. These include the type of coalition present, the age of the patient, the joints affected, and if there are any arthritic changes present. Surgery can include resecting the coalition at the joint level or fusing the involved joints together. In younger patients, a resection (cutting of the bar) is most commonly utilized and is successful. If arthritic changes have developed, a fusion may be the only option.