title: Remodeling of C2 facet deformity prevents recurrent subluxation in patients with chronic atlantoaxial rotatory fixation: a novel strategy for treatment of chronic atlantoaxial rotatory fixation.
abstract: METHODS
  A retrospective case series.
  
  
  OBJECTIVE
  To propose a novel treatment strategy for chronic atlantoaxial rotatory fixation (AARF).
  
  
  BACKGROUND
  Treatment strategy for chronic or recurrent AARF remains controversial. We have previously reported that a deformity of the superior facet of the axis (C2 facet deformity), which is frequently observed in patients with chronic AARFs, is a risk factor for recurrent dislocation. In this article, we report seven consecutive cases of chronic AARF who underwent closed manipulation followed by external halo fixation and maintained good reduction with the remodeling of the C2 facet deformity.
  
  
  METHODS
  Seven girls with a chronic AARF who sustained torticollis for an average of 4.6 months after the onset were referred to our clinic. Closed manipulation by careful manipulation under general anesthesia followed by external immobilization with a halo vest was performed in all cases. Radiographic findings and clinical courses were retrospectively reviewed with approvals by the institutional review board.
  
  
  RESULTS
  Three-dimensional computed tomography images before reduction revealed persistent atlantoaxial subluxation and the C2 facet deformity in the dislocated side in all cases. Follow-up three-dimensional computed tomographic scans demonstrated the remodeling of the C2 facet deformity at an average of 2.8 months after successful reduction of subluxation. Subsequently, the halo vests were removed and gentle neck range of motion exercise was started in all cases. The normal cervical range of motion was obtained 2 weeks after the removal of halo vests in five cases, whereas the range of motion remained limited in two cases. At a mean follow-up of 17.4 months, neither symptoms nor recurrence of subluxation occurred in all cases.
  
  
  CONCLUSIONS
  Chronic irreducible and recurrent unstable AARF can be managed successfully by careful closed manipulation followed by halo fixation, if the C1 and C2 have not been osseously fused. The remodeling of the C2 facet deformity detected on follow-up CT scans can be a useful radiographic parameter to determine the appropriate period of halo fixation in this new treatment strategy obviating the need for surgical intervention.
authors.affiliation: Departments of Orthopaedic Surgery, School of Medicine, Keio University, Shinjuku, Tokyo, Japan.
authors.forename: Ken
authors.initials: K
authors.lastname: Ishii
authors.forename: Morio
authors.initials: M
authors.lastname: Matsumoto
authors.forename: Suketaka
authors.initials: S
authors.lastname: Momoshima
authors.forename: Kota
authors.initials: K
authors.lastname: Watanabe
authors.forename: Takashi
authors.initials: T
authors.lastname: Tsuji
authors.forename: Hironari
authors.initials: H
authors.lastname: Takaishi
authors.forename: Masaya
authors.initials: M
authors.lastname: Nakamura
authors.forename: Yoshiaki
authors.initials: Y
authors.lastname: Toyama
authors.forename: Kazuhiro
authors.initials: K
authors.lastname: Chiba
mesh_terms: D001268:Atlanto-Axial Joint / Q000000981:diagnostic imaging / Q000601:surgery*; D002574:Cervical Vertebrae / Q000002:abnormalities / Q000000981:diagnostic imaging / Q000601:surgery*; D002648:Child; D002675:Child, Preschool; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D004204:Joint Dislocations / Q000150:complications / Q000517:prevention & control / Q000601:surgery*; D019637:Orthopedic Procedures / Q000379:methods; D012008:Recurrence; D012189:Retrospective Studies; D014057:Tomography, X-Ray Computed; D014103:Torticollis / Q000209:etiology / Q000628:therapy; D016896:Treatment Outcome