title: The kinematic relationships of the upper cervical spine.
abstract: METHODS
  A retrospective radiographic study.
  
  
  OBJECTIVE
  To elucidate the kinematic relationships of the upper cervical spine.
  
  
  BACKGROUND
  To our knowledge, few reports have described the kinematic relationships of the upper cervical spine in patients with general age-related cervical spondylosis.
  
  
  METHODS
  We performed Kinetic magnetic resonance imaging for 295 consecutive patients experiencing neck pain without neurologic symptoms. Subjects with rheumatoid arthritis, traumatic history, and severe degenerative changes in the upper cervical spine were excluded. Anterior atlantodens interval (AADI) and the cervicomedullary angle in 3 different postures were measured, and the variations in each value between flexion and neutral (F-N), neutral and extension (N-E), and flexion and extension (F-E) were calculated. The subjects were classified into 3 groups according to the space available for the cord values (A: <or=14 mm, B: 14-15 mm, C: >or=15 mm).
  
  
  RESULTS
  AADI significantly increased from extension to flexion posture, however, no significant differences were observed in every posture among the groups. F-N variation in AADI showed no significant differences among the groups; however, N-E variation between Groups A and C and between Groups B and C and F-E variation between Groups A and C showed significant differences. The cervicomedullary angle significantly increased from flexion to extension posture, however, no significant differences were observed in every posture among the groups. Angle variations among the groups showed no significant differences, except for F-N angle variation between Groups B and C. None of the variations in AADI and the cervicomedullary angle were significantly correlated.
  
  
  CONCLUSIONS
  Our results suggest that only the kinematics of the atlantoaxial movement, especially the posterior movement, was greatly affected by the narrowing of space available for the cord. The central atlantoaxial joint may be closely related to the mechanisms for protecting the spinal cord by restriction of the atlantoaxial movement.
authors.affiliation: Department of Orthopaedic Surgery, University of California at Los Angeles, Los Angeles, CA, USA.
authors.forename: Yuichiro
authors.initials: Y
authors.lastname: Morishita
authors.forename: Jonathan
authors.initials: J
authors.lastname: Falakassa
authors.forename: Masatoshi
authors.initials: M
authors.lastname: Naito
authors.forename: Henry J
authors.initials: HJ
authors.lastname: Hymanson
authors.forename: Cyrus
authors.initials: C
authors.lastname: Taghavi
authors.forename: Jeffrey C
authors.initials: JC
authors.lastname: Wang
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000375:Aging / Q000473:pathology; D001268:Atlanto-Axial Joint / Q000033:anatomy & histology / Q000502:physiology*; D001269:Atlanto-Occipital Joint / Q000473:pathology / Q000503:physiopathology; D001368:Axis, Cervical Vertebra / Q000033:anatomy & histology / Q000000981:diagnostic imaging / Q000502:physiology*; D001696:Biomechanical Phenomena; D001270:Cervical Atlas / Q000033:anatomy & histology / Q000000981:diagnostic imaging / Q000502:physiology*; D004185:Disability Evaluation; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods; D008297:Male; D008875:Middle Aged; D009777:Occipital Bone / Q000473:pathology / Q000503:physiopathology; D011187:Posture / Q000502:physiology; D011859:Radiography; D016059:Range of Motion, Articular / Q000502:physiology*; D012189:Retrospective Studies; D013117:Spinal Cord Compression / Q000473:pathology / Q000503:physiopathology; D013130:Spinal Stenosis / Q000473:pathology / Q000503:physiopathology; D055009:Spondylosis / Q000473:pathology / Q000503:physiopathology*; D055815:Young Adult