Talocalcaneal Coalition

Excerpt

The talocalcaneal coalition is a frequent cause of painful flatfoot in older children or adolescents. The talocalcaneal coalition is an anomalous connection between the talus and the calcaneus. The talocalcaneal coalition can be fibrous (syndesmosis), cartilaginous (synchondrosis), or bony (synostosis). Although the anomaly is present at birth, it becomes symptomatic only when the abnormal fibrous connection matures into a stiff cartilaginous bar and, over time, ossifies to become a rigid bar. The age of onset is typically between 12 to 15.

It is described as a peroneal spastic flat foot as the peroneal muscles spasm in a painful, rigid flat foot. Peroneal spasm tends to refer to the contracted peroneal tendons in a rigid flatfoot, however only 3.13% of patients with talocalcaneal coalitions present with this symptom.

The subtalar joint has 3 facets: anterior, middle, and posterior, that articulate with the respective facets of the calcaneum. Historically, the middle facet is described as being the most commonly involved in talocalcaneal coalitions. However, other authors reported the posterior facet having a higher involvement rate than the middle facet. The middle facet is most commonly involved in the talocalcaneal coalition. The posterior facet is the largest, and the anterior facet is the smallest. 4 recognized anatomical patterns of the anterior and middle facets: a single small middle facet, a large middle facet that extends posteriorly, a middle facet that extends anteriorly, and both facets-middle and anterior in the medial compartment. The size of the talocalcaneal coalition determines the successful outcome after its resection.

The talocalcaneal coalition is the second most common tarsal coalition in the foot after the calcaneonavicular coalition. Tarsal coalitions cause gradual flattening of the medial longitudinal arch, resulting in a flat foot and stiffness of the subtalar joint.

Archaeological evidence points to the presence of the tarsal coalitions in the Mayan and pre-Columbian Indian civilizations. Zuckerkandl described the anatomy of a talocalcaneal coalition in 1877. Slomann (1921), Badgeley (1927), and Harris and Beath (1948) associated the tarsal coalitions with peroneal spastic feet.