title: Recurrent dislocations of the atlantooccipital and atlantoaxial joints in a halo vest fixator are resolved by backrest elevation in an elevation angle-dependent manner.
abstract: BACKGROUND
  Halo fixation is now universally performed in the initial reduction and fixation of unstable upper cervical spine injuries; however, persistent high instability and recurrent dislocations of the atlantooccipital and atlantoaxial joints after fixation are not well recognized.
  
  
  OBJECTIVE
  The aim was to describe persistent instability of traumatic dislocations of the atlantooccipital and atlantoaxial joints after halo fixation and a useful method for preventing instability.
  
  
  METHODS
  This was a case report of a patient who survived traumatic dislocations of the atlantooccipital and atlantoaxial joints.
  
  
  METHODS
  A 73-year-old woman diagnosed with dislocations of the atlantooccipital and atlantoaxial joints along with multiple other injuries sustained in a traffic accident was included.
  
  
  METHODS
  After initial closed reduction and halo fixation, congruity of the atlantooccipital and atlantoaxial joints was evaluated using, condylar gap, atlantodental interval, and flexion angulation of C1-C2 after the initial examination and before surgery.
  
  
  RESULTS
  Changes in parameters 12 hours after halo fixation revealed re-dislocations and instability of the joints. Backrest elevation with halo fixation tended to reduce re-dislocations. Therefore, we carefully increased the backrest angle and measured the parameters at several angles of elevation within a range that did not affect vital signs to observe the effectiveness of elevation against re-dislocations. Elevation changed the parameters in an elevation angle-dependent manner, and these changes suggested that elevation was effective for reducing re-dislocation of both the atlantooccipital and atlantoaxial joints during halo fixation. With no major complications, this method enabled us to maintain good congruity of the joints for approximately 2 weeks until posterior spinal fusion with internal fixation.
  
  
  CONCLUSIONS
  Backrest elevation with halo fixation appears safe to be performed without any other devices and is beneficial for blocking re-dislocation of both the atlantooccipital and atlantoaxial joints as well as possible secondary damage to the upper cervical spinal cord during the external fixation period.
authors.affiliation: Department of Spine Surgery, Saga-Ken Medical Centre Koseikan, 400 Nakabaru, Kase-machi, Saga 840-8571, Japan; Department of Trauma Centre, Saga-Ken Medical Centre Koseikan, 400 Nakabaru, Kase-machi, Saga, 840-8571, Japan. Electronic address: gkato23@yahoo.co.jp.
authors.forename: Go
authors.initials: G
authors.lastname: Kato
authors.affiliation: Department of Spine Surgery, Saga-Ken Medical Centre Koseikan, 400 Nakabaru, Kase-machi, Saga 840-8571, Japan.
authors.forename: Kenichi
authors.initials: K
authors.lastname: Kawaguchi
authors.affiliation: Department of Trauma Centre, Saga-Ken Medical Centre Koseikan, 400 Nakabaru, Kase-machi, Saga, 840-8571, Japan; Department of Orthopaedic Surgery, Saga-Ken Medical Centre Koseikan, 400 Nakabaru, Kase-machi, Saga, 840-8571, Japan.
authors.forename: Nobuaki
authors.initials: N
authors.lastname: Tsukamoto
authors.affiliation: Department of Trauma Centre, Saga-Ken Medical Centre Koseikan, 400 Nakabaru, Kase-machi, Saga, 840-8571, Japan; Department of Orthopaedic Surgery, Saga-Ken Medical Centre Koseikan, 400 Nakabaru, Kase-machi, Saga, 840-8571, Japan.
authors.forename: Keisuke
authors.initials: K
authors.lastname: Komiyama
authors.affiliation: Department of Orthopaedic Surgery, Saga-Ken Medical Centre Koseikan, 400 Nakabaru, Kase-machi, Saga, 840-8571, Japan.
authors.forename: Kazutaka
authors.initials: K
authors.lastname: Mizuta
authors.affiliation: Department of Emergency Medicine, Saga-Ken Medical Centre Koseikan, 400 Nakabaru, Kase-machi, Saga, 840-8571, Japan.
authors.forename: Takayuki
authors.initials: T
authors.lastname: Onohara
authors.affiliation: Department of Orthopaedic Surgery, Kumamoto Red Cross Hospital, 2-1-1 Reinan, Higashi-ku, 861-8039, Kumamoto, Japan.
authors.forename: Hirofumi
authors.initials: H
authors.lastname: Okano
authors.affiliation: Department of Orthopaedic Surgery, Saga-Ken Medical Centre Koseikan, 400 Nakabaru, Kase-machi, Saga, 840-8571, Japan.
authors.forename: Shunsuke
authors.initials: S
authors.lastname: Hotokezaka
authors.affiliation: Department of Trauma Centre, Saga-Ken Medical Centre Koseikan, 400 Nakabaru, Kase-machi, Saga, 840-8571, Japan; Department of Orthopaedic Surgery, Saga-Ken Medical Centre Koseikan, 400 Nakabaru, Kase-machi, Saga, 840-8571, Japan.
authors.forename: Takao
authors.initials: T
authors.lastname: Mae
mesh_terms: D000368:Aged; D001268:Atlanto-Axial Joint / Q000473:pathology*; D005260:Female; D005592:Fracture Fixation; D006801:Humans; D004204:Joint Dislocations / Q000601:surgery*; D009989:Orthotic Devices; D013124:Spinal Injuries / Q000601:surgery*
keywords: Atlantoaxial; Atlantooccipital; Dislocation; External fixation; Halo vest; Preoperative management; Re-dislocation; Trauma