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Congenital bipartite lunate presenting as a misdiagnosed lunate fracture: a case report
© Loh et al; licensee BioMed Central Ltd. 2011
Received: 19 January 2010
Accepted: 14 March 2011
Published: 14 March 2011
A rare case of congenital bipartite lunate in a child is reported. Carpal variants are very uncommon as independent entities, with only three previous reports of this condition in the English literature.
An 11-year-old Caucasian boy presented with pain in the left wrist after a fall. Radiographs in the emergency department demonstrated a lunate that was divided into palmar and dorsal parts, causing a misdiagnosis of fractured lunate. Magnetic resonance imaging was then used to differentiate between the two diagnoses.
Very few cases of bipartite lunate have been reported in the literature, and unless awareness is raised about congenital anomalies such as this variant, confusion may arise.
The bipartite lunate is a rare congenital variation of the carpal bones. While anomalies such as a bipartite scaphoid, bipartite hamate and carpal synostosis are well described in the literature [1–4], to our knowledge only three cases involving the lunate have previously been reported [5–7]. Here we demonstrate the radiographic imaging from an interesting case of congenital bipartite lunate that was initially misdiagnosed as a fracture in the context of trauma.
The lunate begins to chondrify at Streeter's 18th and 19th horizons of embryonic development . It usually has one center of ossification that appears by the age of two years, but double-ossification centers in the lunate have been noted . Variation in lunate ossification is known, with ossification beginning between the ages of one and a half to seven years in boys and between one and six years of age in girls until completion between the ages of 12 to 14 for both genders .
As previously mentioned, congenital bipartite lunate is a rare occurrence and may lead to diagnostic difficulties in the setting of acute wrist trauma and pain. However, we did not consider the divided lunate to be a fracture, because the MRI and plain radiograph images showed that each part was well corticated with no evidence of callus formation. We concluded that our case was also unlikely to be pseudoarthrosis after a previous lunate fracture because there was neither a history of trauma to the wrist nor evidence of degenerative change. Last, the patient did not display any radiographic signs suggestive of Kienböck's disease, such as lunate fragmentation due to devascularized, necrotic bone and decreased T1-weighted signal intensity on MRI images .
Injuries to the wrist and carpal bones are extremely common, and unless there is awareness about congenital anomalies such as the bipartite lunate, scaphoid and hamate, confusion and misdiagnoses may arise.
Written informed consent was obtained from the parents of the patient for publication of this case report and accompanying images. A copy of the written consent is available for review by the Editor-In-Chief of this journal.
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