In talocalcaneal coalitions, the Halo sign or C-sign is outlined by the talar dome and which other structure?

• A. Navicular bone
• B. Sustentaculum tali
• C. Cuboid bone
• D. Calcaneus

Answer: (B)

The Halo sign or C-sign observed in talocalcaneal coalitions is specifically delineated by the talar dome and the sustentaculum tali. This sign is important in the radiographic assessment of talocalcaneal coalitions, which are abnormal connections between the talus and calcaneus bones that can lead to various foot pathologies.

The sustentaculum tali is a bony shelf-like structure on the calcaneus that supports the talus. Its proximity to the talar dome allows for a distinct radiological appearance when assessed in cases of coalition. This anatomical relationship helps in visualizing and diagnosing the coalition itself by highlighting the abnormal contour and relationship between these structures on imaging studies.

The navicular bone, cuboid bone, and calcaneus are important structures in foot anatomy; however, they do not create the specific Halo or C-sign in the context of talocalcaneal coalitions. Understanding the interaction between the sustentaculum tali and the talar dome is crucial for accurate diagnosis and subsequent management of the coalition.