title: Atlantoaxial instability associated with an orthotopic os odontoideum: a multimodality imaging assessment.
abstract: Radiography, computed tomography (CT), and magnetic resonance imaging exams of the cervical spine were performed in a 29-year-old man who was ultimately diagnosed with an orthotopic os odontoideum during admission for injuries sustained in a motor vehicle collision. Initial radiography suggested either os odontoideum or an acute fracture of the dens. Further imaging with CT and flexion and extension radiographs confirmed os odontoideum and excluded a dens fracture. Although rare, os odontoideum is an important cervical spine anomaly to consider and to distinguish from an acute fracture of the dens.
authors.affiliation: Brigham and Women's Hospital, 75 Francis Street, Boston, MA, 02115, USA.
authors.forename: Tomas M
authors.initials: TM
authors.lastname: Vargas
authors.forename: Frank J
authors.initials: FJ
authors.lastname: Rybicki
authors.forename: Stephen M
authors.initials: SM
authors.lastname: Ledbetter
authors.forename: John D
authors.initials: JD
authors.lastname: MacKenzie
mesh_terms: D000328:Adult; D001268:Atlanto-Axial Joint / Q000473:pathology*; D006801:Humans; D007593:Joint Instability / Q000175:diagnosis* / Q000473:pathology; D008279:Magnetic Resonance Imaging; D008297:Male; D009809:Odontoid Process / Q000473:pathology*; D014057:Tomography, X-Ray Computed