“ Abnormal union of the bones of the mid-foot or hind-foot; union is either cartilaginous, fibrous or bony. The site of union is commonly ei...
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Abnormal union of the bones of the mid-foot or hind-foot; union is either cartilaginous, fibrous or bony. The site of union is commonly either the calcaneonavicular joint (45%) or the subtalar joint (45%). Coalitions restrict movement of the mid-foot and cause pain and pes planus.
PLAIN FILM
• With fibrous/cartilaginous coalition, look for joint space narrowing, indistinct articular margins and reactive sclerosis.
• Calcaneonavicular coalition best seen on an oblique, look for:
– Elongated tubular extension of the anterior calcaneus, which fuses with the dorsolateral margin of the navicular.
– Elongated calcaneus known as the ‘anteater sign’.
• Talocalcaneal coalition:
– Difficult to assess on standard views.
– Look for a ‘talar beak’.
– ‘C-sign’ (lateral view) is a c-shaped sclerotic line extending between the posterior surface of the talus and the sustentaculum tali.
MRI
• Sagittal/axial best for calcaneonavicular coalition, coronal for talocalcaneal.
• More sensitive than CT for non-osseus coalition.
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