Corpus: Talonavicular coalition

The talonavicular coalition is a rarely occurring synostosis between the talus and the navicular bone (Os naviculare). It belongs to the tarsal coalitions.

• ICD10 code: Q66.8 - Other congenital deformities of the feet

Talonavicular coalition results from a segmentation disorder during embryonic development that leads to incomplete separation of the two bones involved.

The talonavicular coalition is already present in early childhood as a soft tissue connection (syndesmosis, synchondrosis) and then ossifies over time. Clinically, there is usually a flat foot, rarely a hollow foot. The medial longitudinal arch is flattened and mobility in the hindfoot is restricted. Patients report frequent twisting of the ankle and increasing pain.

• Conventional X-ray, special images from a certain angle are often necessary
• Computed tomography
• MRI (for the detection of connective tissue adhesions)