title: Sequential imaging demonstrating os odontoideum formation after a fracture through the apical odontoid epiphysis: case report and review of the literature.
abstract: BACKGROUND
  The mechanism of formation of an os odontoideum is controversial and likely multifactorial. One theory states that the apex of the odontoid separates from the body because of a fracture. The intact alar and apical ligaments pull the fractured segment superiorly. The independent vascular supply of the apex allows the fractured bone to remain viable and remodel into the smooth, corticated bone characteristic of an os odontoideum. However, there are no publications with direct radiographic evidence supporting the theory.
  
  
  METHODS
  In this paper, the authors present a 7-year-old child with a fracture through the apical odontoid epiphysis, extending into the body of the dens. Serial imaging studies demonstrate progressive separation of the apex from the body of the odontoid. The fractured segment begins to remodel and assume the classic form of an os.
  
  
  CONCLUSIONS
  The authors consider this case to be radiographic evidence supporting an acquired/traumatic origin of os odontoideum. Further, the mechanism of fracture through a cartilaginous epiphysis may explain the formation of an os after "normal" x-ray images or following seemingly minor trauma.
authors: Department of Neurosurgery, Indiana University School of Medicine, Indianapolis, IN, USA.
authors: Ian K
authors: IK
authors: White
authors: Kevin J
authors: KJ
authors: Mansfield
authors: Daniel H
authors: DH
authors: Fulkerson
mesh_terms: D002648:Child; D004838:Epiphyses / Q000000981:diagnostic imaging*; D006801:Humans; D008297:Male; D009809:Odontoid Process / Q000000981:diagnostic imaging* / Q000293:injuries; D011859:Radiography; D016103:Spinal Fractures / Q000000981:diagnostic imaging*
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