Understanding Tarsal Coalition: A Comprehensive Overview

Tarsal coalition is a condition where there is an abnormal connection between two or more tarsal bones in the foot. This condition is primarily congenital, resulting from a failure in the segmentation of mesenchymal tissue during fetal development. While many cases remain asymptomatic, tarsal coalitions can cause significant pain and deformity, often leading to challenges in daily activities. Here, we explore the causes, symptoms, diagnosis, and treatment of tarsal coalitions, focusing on the two most common forms: talocalcaneal and calcaneonavicular coalitions.

What is Tarsal Coalition?

Tarsal coalition refers to the bridging of two tarsal bones in the foot, which can involve bone, cartilage, or fibrous tissue. The condition is usually congenital but may also be acquired due to trauma or disease. The abnormal connection results in restricted motion of the affected foot, causing pain and deformities such as flatfoot and valgus (inward tilt of the heel). This condition typically presents in childhood or adolescence, often after a minor injury or repeated sprains.

Causes and Types

Tarsal coalitions are most commonly caused by a failure in the differentiation of mesenchymal embryonic tissue during foot development. This leads to an incomplete segmentation of the tarsal bones. The genetic basis for this condition has been linked to mutations, such as a Pro250Arg mutation in the fibroblast growth factor receptor 3 (FGFR3) gene, which may predispose individuals to develop tarsal coalitions.

There are several types of tarsal coalitions, depending on the bones involved:

1. Talocalcaneal Coalition: Involves the talus and calcaneus (heel bone). It is the most common form, responsible for about 48% of cases.
2. Calcaneonavicular Coalition: Involves the calcaneus and navicular bones, and is the second most common.
3. Other Types: Including talonavicular, calcaneocuboid, and naviculocuneiform coalitions, though these are less prevalent.

Symptoms of Tarsal Coalition

The primary symptom of tarsal coalition is pain in the foot, which can be diffuse or localized, depending on the type of coalition. Pain usually occurs during physical activity and may be triggered by minimal trauma. In cases of calcaneonavicular coalition, pain is often felt at the front of the foot. For talocalcaneal coalitions, pain tends to be localized below the medial malleolus (inside ankle). Over time, the coalition may cause a loss of the medial longitudinal arch, leading to rigid and painful flatfoot (pes planovalgus).

Other symptoms include:

• Restricted Subtalar Motion: The normal motion between the talus and calcaneus is often blocked, causing stiffness.
• Recurrent Ankle Sprains: As a result of limited joint mobility, patients often experience frequent sprains, especially during activities requiring ankle rotation.
• Foot Deformities: Deformities such as heel valgus (tilting inward) or forefoot abduction (turning outward) are common.

Diagnosing Tarsal Coalition

Diagnosis begins with a thorough physical examination and radiographic imaging. Initial evaluation typically involves weight-bearing X-rays, including anteroposterior, lateral, and oblique views. For calcaneonavicular coalitions, the “anteater nose” sign seen on the oblique X-ray is characteristic, while talocalcaneal coalitions may show a “C” sign on lateral X-rays. If these methods are inconclusive, advanced imaging techniques like computed tomography (CT) and magnetic resonance imaging (MRI) are used to visualize the coalition more accurately, especially when the condition is in its fibrous or cartilaginous stage.

Treatment of Tarsal Coalition

Treatment for tarsal coalition depends on the severity of the symptoms and the type of coalition. The goal of treatment is to relieve pain, restore foot function, and prevent further deformity.

Conservative Treatment

In many cases, conservative measures are effective, especially when the condition is detected early and is not causing significant deformity. Conservative treatments include:

• Nonsteroidal Anti-Inflammatory Drugs (NSAIDs): For pain relief.
• Orthotics: Custom shoe inserts or braces can help support the foot and reduce symptoms.
• Casting: For patients with significant pain, casting may be used to immobilize the foot and reduce inflammation.

Surgical Treatment

When conservative treatment fails or the patient develops significant deformities, surgery may be required. The most common surgical procedures include:

• Resection of the Coalition: This is the most common procedure for both talocalcaneal and calcaneonavicular coalitions. The coalition is surgically removed, and tissue grafts (such as the extensor digitorum brevis muscle or fat grafts) may be used to fill the resection gap and reduce the risk of recurrence.
• Valgus Correction: In cases of significant foot deformity, additional procedures like Achilles tendon lengthening or osteotomy may be performed to correct the alignment of the foot.
• Arthrodesis: In cases of advanced degenerative arthritis or when other surgical treatments fail, fusion of the affected joints may be necessary.

Prognosis

The prognosis after treatment of tarsal coalition is generally good, particularly for younger patients undergoing coalition resection. Surgery often provides significant pain relief, improves foot function, and prevents further deformity. However, in cases where degenerative changes are advanced, surgical outcomes may be less favorable, and a more extensive procedure such as triple arthrodesis may be required.

Conclusion

Tarsal coalition is a condition that can lead to significant pain and functional limitations if left untreated. Early diagnosis and appropriate treatment, whether conservative or surgical, are crucial to restoring foot function and preventing long-term complications. If you suspect tarsal coalition, particularly if you experience frequent ankle sprains or foot pain, it is important to seek medical advice and consider appropriate imaging to confirm the diagnosis.