J Korean Radiol Soc.  2001 May;44(5):623-628. 10.3348/jkrs.2001.44.5.623.

Subtalar Coalition: Usefulness of the C Sign on Lateral Radiographs of the Ankle

• Kim SH
• Ahn JM
• Kim SM
• Lee MH
• Yoon HK
• Shin MJ
• Kang HS

• KMID: 1583079
• DOI: http://doi.org/10.3348/jkrs.2001.44.5.623

Abstract

PURPOSE: To assess the usefulness of the talocalcaneal C sign in the diagnosis of subtalar coalition, as seen on lateral radiographs of the ankle.
MATERIALS AND METHODS
Lateral radiographs of 12 ankles in 11 patients were included in this study. Twelve subtalar coalitions were confirmed by surgery (n=6), or by CT and/or MR (n=6). The presence of the talocal-caneal C sign on lateral ankle radiographs was determined.
RESULTS
The C sign was continuous in six feet and interrupted in the remaining six. Subtalar coalition occurred simultaneously in the middle and posterior subtalar joints in two cases, the posterior subtalar joint only in six, and in the middle subtalar joint only in four. In six cases confirmed at surgery, subtalar coalitions consisted of both synostosis and non-osseous fusion (synchondrosis and/or syndesmosis) and in one case of middle subtalar coalition, there was a bony bridge. The remaining six cases, confirmed at CT or MRI, involved both synostosis and non-osseous fusion (n=1) or non-osseous fusion only (n=5).
CONCLUSION
In the diagnosis of subtalar coalition, the talocalcaneal C sign, seen on lateral radiographs of the ankle, is a useful indicator.

Keyword

Ankle; Ankle, abnormalities; Computed tomography (CT); Ankle, MR

MeSH Terms

Ankle*
Diagnosis
Foot
Humans
Magnetic Resonance Imaging
Subtalar Joint
Synostosis