The pathogenesis of Kirner's deformity: A clinical, radiological and histological study.

UNLABELLED: The distal phalanx in Kirner's disease is abnormal and recognizable both clinically and radiologically. Despite previous investigation, the cause of these abnormalities is not clear. The current study seeks to evaluate the abnormal physis in Kirner's deformity using radiological investigation, intraoperative observation and histopathological assessment in three clinical cases. Similarities with clinodactyly are described. Three patients with Kirner's deformity underwent plain-film radiography and magnetic resonance imaging. Intraoperative observations were recorded, and histologic assessment of anatomically abnormal tissue was performed in all three cases. All three modalities of investigation (plain-film X-rays, magnetic resonance imaging and histological findings) were consistent and supported the intraoperative observation of cartilage abnormally situated anterior to the diaphysis and deep to the flexor tendon. There is thus evidence for the presence of an incomplete volar bracket or L-shaped physis in Kirner's deformity, analogous with the C-shaped bracket found in clinodactyly. LEVEL OF EVIDENCE: Aetiological Study; Level 4.