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Hamate and pisiform coalition: a case report and introduction to the carpal C-sign on lateral radiograph
Jonathan Cortese1, Marc Soubeyrand2, Leo Razakamanantsoa3
1Radiology Department, Hôpital Bicêtre, 78 rue du Général Leclerc, 94266, Le Kremlin-Bicetre, France. jon.cortese@live.fr.
Abstract:
Hamate-pisiform coalition is an exceptional form of carpal coalition. Case reports are essential to gain a better understanding of this variant. We report a case of congenital bilateral hamate-pisiform coalition in a 20-year-old male discovered in the context of a right wrist trauma. Radiographs also revealed a bilateral scapholunate diastasis. Clinical examination and radiological findings suggested that the right wrist scapholunate diastasis was related to scapholunate instability. Left wrist scapholunate diastasis could be related to (1) a pathological feature or (2) a normal variant associated with hamate-pisiform coalition. Lateral radiographs showed a volar C-shaped osseous bridge corresponding to the coalition. We associated it with a new sign: the "carpal C-sign". Computed tomography with three-dimensional reconstruction provides helpful information about the type of coalition (osseous versus non-osseous) and excludes potential fracture. We discuss the specific embryologic features of the hamate-pisiform coalition, as well as its prevalence, radiographic classification, clinical significance, and treatment.
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