title: Os odontoideum: etiology, diagnosis, and management.
abstract: BACKGROUND
  There have been few reports of os odontoideum since the initial description.
  
  
  METHODS
  Forty-four patients with os odontoideum treated during the period 1980 through 1996 were reviewed. There were 33 males and 11 females. Their ages ranged from 7 to 56 years, with an average of 24.6 years. Five patients with no symptoms were treated conservatively. Thirty-nine patients underwent operative treatment including nine posterior atlantoaxial fusions and 33 occipitocervical fusions.
  
  
  RESULTS
  The patients were followed up for one to 16 years, with an average of 6.5 years. Five patients treated conservatively have remained stable. All 39 treated patients achieved solid arthrodesis. The results were satisfactory.
  
  
  CONCLUSIONS
  We conclude that fusion is indicated if atlantoaxial instability or clinical symptoms are significant, and that occipitocervical fusion should be considered in the operative management of os odontoideum if atlantoaxial arthrodesis is impossible.
authors.affiliation: Department of Orthopaedic Surgery, Changzheng Hospital, The Second Military Medical University, Shanghai, China.
authors.forename: L
authors.initials: L
authors.lastname: Dai
authors.forename: W
authors.initials: W
authors.lastname: Yuan
authors.forename: B
authors.initials: B
authors.lastname: Ni
authors.forename: L
authors.initials: L
authors.lastname: Jia
mesh_terms: D000293:Adolescent; D000328:Adult; D001268:Atlanto-Axial Joint / Q000601:surgery; D002574:Cervical Vertebrae / Q000601:surgery; D002648:Child; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009809:Odontoid Process / Q000601:surgery; D013118:Spinal Cord Diseases / Q000209:etiology; D013122:Spinal Diseases / Q000150:complications / Q000175:diagnosis / Q000209:etiology / Q000601:surgery / Q000628:therapy; D013123:Spinal Fusion / Q000379:methods