Calcaneonavicular coalition
Calcaneonavicular coalition is one of the two most common subtypes of the tarsal coalition, the other being talocalcaneal coalition. As with any coalition it may be osseous (synostosis), cartilaginous (synchondrosis) or fibrous (syndesmosis).
Radiographic features
This type of coalition is more easily diagnosed on plain film than talocalcaneal coalition.
Plain radiograph
Oblique view
- best at depicting calcaneonavicular coalition directly as a calcaneonavicular bar
AP view
- may also directly show the coalition
- indirect signs include
- the broad proximal surface of navicular: broader than the articulating talar head
- lateral tapering of navicular
Lateral view
Indirect signs include:
- anteater sign: an elongated anterior process of the calcaneus
- reverse anteater sign: elongated lateral navicular
- talar beak
- short talar neck
CT
CT can be used to confirm the diagnosis where this was equivocal or not seen on plain films. It may also be used for surgical planning.
MRI
MRI is probably more helpful in assessing and characterizing cartilaginous and fibrous coalition and allows assessment of associated bone and soft tissue edema.
Treatment and prognosis
As with any tarsal coalition, non-operative management may allow some improvement in symptoms initially, but they usually return. Usually, surgical treatment with excision of the coalition is required.
Related Radiopaedia articles
Anatomy: Lower limb
- skeleton of the lower limb
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hip joint
- ligaments
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hip bursae
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- postero-inferior
- anterior
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knee joint
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posterolateral ligamentous complex
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ankle joint
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subtalar joint
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tarsometatarsal (Lisfranc) joint
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subtalar joint
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hip joint
- spaces of the lower limb
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muscles of the lower limb
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