C sign (talocalcaneal coalition)

The C sign is an important radiological sign which may be seen on a lateral radiograph of ankle in those with a  tarsal coalition (talocalcaneal coalition). 

Radiographic appearance

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.

Differential diagnosis

Possible differential considerations include:

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Article Information

rID: 25694
Sections: Gamuts, Signs
Synonyms or Alternate Spellings:
  • C sign of tarsal coalition
  • C sign of talocalcaneal coalition
  • Calcaneal C sign

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