The C sign is an important radiological sign which may be seen on a lateral radiograph of the ankle in those with a tarsal coalition (talocalcaneal coalition).
A continuous C-shaped arc is seen on a lateral ankle radiograph which is formed by the medial outline of the talar dome and posteroinferior aspect of the sustentaculum tali.
Possible differential considerations include:
- subtalar syndesmosis or synchondrosis: CT is helpful in differentiating
- positional artefact
- 1. A. Sakellariou. Talocalcaneal coalition. J Bone Joint Surg Br. 2000;82-B (4): 574-578. J Bone Joint Surg Br (abstract)
- 2. Kim SH. The C sign. Radiology. 2002;223 (3): 756-7. Radiology (full text) - doi:10.1148/radiol.2233991817 - Pubmed citation
- 3. Crim JR, Kjeldsberg KM. Radiographic diagnosis of tarsal coalition. AJR Am J Roentgenol. 2004;182 (2): 323-8. doi:10.2214/ajr.182.2.1820323 - Pubmed citation
- 4. Bohne WH. Tarsal coalition. Curr. Opin. Pediatr. 2001;13 (1): 29-35. Pubmed citation