Tarsal coalition
- Tarsal coalition represents abnormal fusion between two or more tarsal bones and is a frequent cause of foot and ankle pain.
- Calcaneonavicular and talocalcaneal coalitions are encountered most frequently; fusion at other sites is much less common. 
- Tarsal coalitions may be:
Osseous
Cartilaginous
Fibrous
- Osseous
- Cartilaginous
- Fibrous
- Initially, all patients with tarsal coalition are treated conservatively with orthotics, casting, nonsteroidal anti-inflammatory medications, steroid injections, or physical therapy.
- Many patients fail conservative therapy and are then treated operatively.
Calcaneonavicular coalitions may be treated with resection.
Talocalcaneal coalitions are treated surgically with resection of the middle facet bony bridge, often with fat interposition.
- Calcaneonavicular coalitions may be treated with resection.
- Talocalcaneal coalitions are treated surgically with resection of the middle facet bony bridge, often with fat interposition.

# Diagnostic Findings for Tarsal coalition

## Radiographs
- Use of conventional radiography alone is often sufficient to diagnose most calcaneonavicular and talonavicular coalitions

### Calcaneonavicular Coalition
- Calcaneonavicular coalitions are best depicted on 45 internal oblique radiographs.
- The calcaneus and navicular do not normally articulate. With osseous coalition, a bony bar that bridges the two bones is seen.
- With fibrous or cartilaginous coalition, the bones are in close proximity, both have irregular surfaces, and the anteromedial calcaneus is abnormally widened or flattened.
- On lateral radiographs, elongation of the anterior dorsal calcaneus may simulate an anteater's nose.
- Hypoplasia of the talus may also be observed with calcaneonavicular coalition.

### Talocalcaneal Coalition
- The subtalar joint consists of the anterior, middle, and posterior facets.
- Talocalcaneal fusion most commonly involves the middle facet at the level of the sustentaculum tali.
- Talocalcaneal coalitions may be difficult to visualize on the three standard radiographic views of the foot because of the complex orientation of the subtalar joint.
- A number of secondary radiographic signs of talocalcaneal coalition have been described, including a talar beak, narrowing of the posterior subtalar joint, rounding of the lateral talar process, and lack of depiction of the middle facets on lateral radiographs
A talar beak occurs because of impaired subtalar joint motion, which results in the navicular overriding the talus.
- A talar beak occurs because of impaired subtalar joint motion, which results in the navicular overriding the talus.
- Another radiographic finding seen on lateral views in talocalcaneal coalition is the C sign.
A C-shaped line outlines the medial talar dome and posteroinferior sustentaculum.
The C sign results from bone bridging between the talar dome and sustentaculum, as well as the prominent inferior outline of the sustentaculum.
The C sign may be observed in both osseous and nonosseous coalitions. Variations in sustentacular size and orientation may affect the reliability of this sign.
- A C-shaped line outlines the medial talar dome and posteroinferior sustentaculum.
- The C sign results from bone bridging between the talar dome and sustentaculum, as well as the prominent inferior outline of the sustentaculum.
- The C sign may be observed in both osseous and nonosseous coalitions. Variations in sustentacular size and orientation may affect the reliability of this sign.

# Clinical Findings

## Calcaneonavicular coalition

## Radiographs and CT demonstrate talocalcaneal and calcaneonavicular coalition