title: Novel 2 radiographical measurements for atlantoaxial instability in children with Down syndrome.
abstract: METHODS
  A retrospective case-control study.
  
  
  OBJECTIVE
  To assess the usefulness and reproducibility of 2 novel safe and simple radiographical measurements for atlantoaxial instability in children with Down syndrome.
  
  
  BACKGROUND
  In pediatric atlantoaxial instability, early diagnosis is important for improved outcomes because of poor postoperative recovery in progressed neurological symptoms. Conventional dynamic radiography of the cervical spine is associated with a potential risk of worsening neurological symptoms.
  
  
  METHODS
  We retrospectively reviewed the medical records of 50 patients (24 boys and 26 girls) with atlantoaxial instability associated with Down syndrome. Of the 50 children, 11 had undergone and 4 had been scheduled for surgery (surgical group). In this investigation, in addition to the atlas-dens interval (ADI) and space available for spinal cord (SAC), we measured C1 inclination angle and C1/4 SAC ratio on lateral radiographs of the cervical spine in the neutral position. To assess the diagnostic abilities of these indices to determine indication for surgery, receiver operating characteristic analysis of each index was performed, and their diagnostic abilities were compared using the area under the receiver operating characteristic curve. Moreover, we assessed reproducibility of our 2 proposed indices.
  
  
  RESULTS
  The discriminatory abilities of C1/4 SAC ratio (area under the receiver operating characteristic curve, 1.00) and C1 inclination angle (0.91) were comparable with those of ADI (0.98) and SAC (0.95). For the interobserver and intraobserver reliability of the novel indices, the correlation coefficients were in the range from 0.88 to 0.99. Correlation was observed between the ADI and C1/4 SAC ratio (r = 0.507, P < 0.01) and between the ADI and C1 inclination angle (r = 0.407, P < 0.01).
  
  
  CONCLUSIONS
  The diagnostic abilities of the 2 novel radiographical measurements were comparable with those of ADI and SAC. Moreover, these novel measurements can be obtained safely on lateral radiographs of the cervical spine in the neutral position.
  
  
  METHODS
  4.
authors.affiliation: *Department of Orthopedic Surgery, Kanagawa Children's Medical Center, Yokohama, Japan †Department of Orthopedic Surgery, School of Medicine, Yokohama City University, Yokohama, Japan; and ‡Department of Spine and Spinal Cord Surgery, Yokohama Stroke and Brain Center, Yokohama, Japan.
authors.forename: Naoyuki
authors.initials: N
authors.lastname: Nakamura
authors.forename: Yutaka
authors.initials: Y
authors.lastname: Inaba
authors.forename: Masatoshi
authors.initials: M
authors.lastname: Oba
authors.forename: Yoichi
authors.initials: Y
authors.lastname: Aota
authors.forename: Yogen
authors.initials: Y
authors.lastname: Morikawa
authors.forename: Yurika
authors.initials: Y
authors.lastname: Ata
authors.forename: Jiro
authors.initials: J
authors.lastname: Machida
authors.forename: Tomoyuki
authors.initials: T
authors.lastname: Saito
mesh_terms: D000293:Adolescent; D001268:Atlanto-Axial Joint / Q000000981:diagnostic imaging* / Q000601:surgery; D016022:Case-Control Studies; D002574:Cervical Vertebrae / Q000000981:diagnostic imaging* / Q000601:surgery; D002648:Child; D002675:Child, Preschool; D004314:Down Syndrome / Q000150:complications / Q000000981:diagnostic imaging* / Q000601:surgery; D005260:Female; D006801:Humans; D007223:Infant; D007593:Joint Instability / Q000150:complications / Q000000981:diagnostic imaging* / Q000601:surgery; D008297:Male; D011859:Radiography; D015203:Reproducibility of Results; D012189:Retrospective Studies