Tarsal Coalition

Tarsal coalition is fusion of the tarsal bones that leads to a ridged flat foot, foot pain and multiple ankle sprains. Tarsal coalition is a congenital anomaly. There are two types of tarsal coalition are talocalcaneal coalition and calcaneonavicular coalition. Talocalcaneal coalition is a coalition between the talus and the calcaneus. Calcaneonavcular coalition is a coalition between the calcaneus and the navicular. When talocalcaneal coalition occurs, it usually happens around 12-15 years of age. The calcaneonavicular coalition presents at an earlier age. 50% of coalitions are bilateral. About 20% have multiple coalition in the same foot. Coalition may be fibrous, cartilaginous or bony. It occurs due to failure of segmentation. It could be associated with fibular hemimelia or Apert’s syndrome. The patient usually complains of a painful foot, a history of repeated ankle sprains, as well as flatfoot deformity. Tarsal coalition may result in peroneal spastic flat foot. You may also find hind foot valgus. On toe standing the arch does not reconstitute. Heel cord contracture might also be evident during the examination. Furthermore, there might be restricted subtalar joint range of motion. Always check both feet, the condition may be bilateral.

The best study is CT scan. It can determine the size and location of the coalition. MRI is also useful in detecting a fibrous or cartilaginous coalition. AP, lateral, and oblique x-ray views should be obtained. On lateral view x-rays, the calcaneonavicular coalition will show the characteristic “anteater nose sign” which is an elongation of the anterior calcaneal process. The lateral view of a talocalcaneal coalition may show talar beaking which is a type of traction spur that occurs due to limited motion of the subtalar joint. Additionally, the C sign is a radiological sign which may be seen on lateral radiographs. It is the outline of the talar dome and the sustentaculum. A 45 degree oblique view is the best for showing calcaneonavicular coalition. No operative treatment usually consists of NSAIDS, modified activities, or the use of a brace or cast. Surgical treatment for calcaneonavicular coalition usually consists of resection with interposition of the extensor digitorum brevis muscle or a fat graft no matter what the size of the coalition is. Talocalcaneal coalitions that involve less than 50% of the subtalar joint are also resected. A triple arthrodesis is performed for large coalitions, failed resections, or advanced conditions.