title: Risk factors for missed dynamic canal stenosis in the cervical spine.
abstract: METHODS
  Retrospective analysis of kinematic magnetic resonance (MR) images.
  
  
  OBJECTIVE
  To elucidate the distribution and risk factors associated with missed dynamic stenosis in cervical spine.
  
  
  BACKGROUND
  Motion of the cervical spine is widely accepted to be associated with cervical spondylotic myelopathy; however, the distribution and the risk factors for dynamic spinal stenosis are not well understood.
  
  
  METHODS
  A total of 435 symptomatic patients (2610 cervical segments) obtained upright kinematic MR images in neutral, flexion, and extension postures. Spinal cord compression (SCC), spondylolisthesis, disc bulging, angular motion, translational motion, disc degeneration grade, Modic changes, segmental alignment, and developmental stenosis were all evaluated. Cervical segments C2-C3 to C7-T1 were divided into 2 groups, determined by the presence of SCC. After excluding segments with SCC in the neutral position, a multivariate logistic regression model was used to evaluate for associated risk factors of SCC in flexion and extension that were not present in the neutral position.
  
  
  RESULTS
  SCC in neutral position was observed in 5.3% (139/2610) of segments. After excluding these segments, missed dynamic stenosis was found in 8.3% (204/2471) of segments in extension and 1.6% (40/2471) in flexion. Missed dynamic stenosis in both extension and flexion was most frequent at C5-C6. Multivariate logistic regression analysis for dynamic stenosis in extension revealed that disc bulge greater than 2.4 mm, angular motion greater than 4.8°, moderate and severe disc degeneration, segmental kyphosis, and developmental stenosis were significant risk factors. In flexion, significant risk factors were a disc bulge of 1.9 mm or greater, moderate to severe disc degeneration, and segmental kyphosis.
  
  
  CONCLUSIONS
  Dynamic cord compression was most common at the C5-C6 segment. Cervical segments with greater disc bulge, more severe disc degeneration, greater angular motion, segmental kyphosis, and developmental stenosis may be at risk for missed dynamic stenosis.
authors.affiliation: *Department of Orthopaedic Surgery, University of California at Los Angeles; and †Department of Orthopaedic Surgery, Japan Labour Health and Welfare Organization, Spinal Injuries Center, Fukuoka, Japan.
authors.forename: Tetsuo
authors.initials: T
authors.lastname: Hayashi
authors.forename: Jeffrey C
authors.initials: JC
authors.lastname: Wang
authors.forename: Akinobu
authors.initials: A
authors.lastname: Suzuki
authors.forename: Shinji
authors.initials: S
authors.lastname: Takahashi
authors.forename: Trevor P
authors.initials: TP
authors.lastname: Scott
authors.forename: Kevin
authors.initials: K
authors.lastname: Phan
authors.forename: Elizabeth L
authors.initials: EL
authors.lastname: Lord
authors.forename: Monchai
authors.initials: M
authors.lastname: Ruangchainikom
authors.forename: Keiichiro
authors.initials: K
authors.lastname: Shiba
authors.forename: Michael D
authors.initials: MD
authors.lastname: Daubs
mesh_terms: D000328:Adult; D000368:Aged; D002574:Cervical Vertebrae / Q000473:pathology*; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted; D055959:Intervertebral Disc Degeneration / Q000473:pathology*; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D012189:Retrospective Studies; D012307:Risk Factors; D013117:Spinal Cord Compression / Q000473:pathology*; D013130:Spinal Stenosis / Q000473:pathology*; D013168:Spondylolisthesis / Q000473:pathology*; D055815:Young Adult