[C-sign and talocalcaneal coalition]

Talocalcaneal coalition is an abnormal bridge between talus and calcaneus, causing pain and restriction of subtalar movement; its incidence is less than 1 %. The signs and symptoms usually become manifest in the second decade of life with ossification of the lesion. They involve flat foot, peroneal muscle spasm, tarsal tunnel syndrome, or valgus tilt of the heel. The sings need not be noticeable and may appear only as tiredness and vague pain in the hind foot after exercise or an easily twisted ankle. The authors describe the case of talocalcaneal coalition in a 20-year-old man, incidentally diagnosed at ankle fracture. The presence of C-sign led to CT examination and the exact diagnosis. Radiological demonstration of this abnormality may be difficult because plain X-ray images in both projections may show normal findings. Literature data report, in addition to C-sign, further secondary signs of talocalcaneal coalition present on lateral radiographs of the ankle joint. Although these signs do not directly point to talocalcaneal coalition, they reveal abnormal anatomy or movement of the joint and may initiate more thorough examination by CT or MRI and the establishment of an exact diagnosis. Therefore, to know the secondary signs and pay attention to them is very useful.