title: Radiologic Factors Associated With the Dynamic Change of Dural Sac Diameter in Lumbar Spine: A Kinematic MRI Study.
abstract: METHODS
  This is a cross-sectional radiologic study.
  
  
  OBJECTIVE
  The purpose of this study was to assess radiologic features related to dynamic changes of dural sac diameter using kinematic magnetic resonance imaging.
  
  
  BACKGROUND
  It is well known that the cross-sectional area of the lumbar spinal canal decreases during movement from flexion to extension. However, the radiologic characteristics related to dynamic changes of the lumbar spinal canal have not been elucidated.
  
  
  METHODS
  A total of 453 consecutive patients with clinically symptomatic low back pain or radiculopathy were recruited to undergo lumbar kinematic magnetic resonance imaging. The study participants consisted of 271 males (60%) and 182 females (40%). The average age was 44.5±12.2 years old. We investigated the following measurements at each level from L3-L4 to L5-S1: dural sac diameter, ligamentum flavum thickness, disk bulge, disk degeneration, angular motion, translational motion, and posterior disk height. The odds ratios (ORs) for ≥2 mm change of dural sac diameter between flexion and extension were calculated.
  
  
  RESULTS
  The average dural sac diameter was 12.2 mm in neutral, 12.5 mm in flexion, and 11.7 mm in extension, with an average difference between flexion and extension of 0.83 mm. The OR of a ≥2 mm change in L5-S1 was 0.55 as compared with L3-L4. Significantly increased ORs were observed with ≥3 mm of ligamentum flavum in neutral (OR: 4.05), 3-3.9 and ≥4 mm of disk bulge in neutral (ORs: 1.62 and 1.81, respectively), grade IV and V disk degeneration (OR: 2.59 and 2.86, respectively), ≥8 degrees of angular motion (OR: 1.81), and ≥2 mm of posterior disk height change (OR: 1.84).
  
  
  CONCLUSIONS
  Several radiologic characteristics related to the dynamic change of dural sac diameter have been demonstrated.
authors.affiliation: *Department of Orthopaedic Surgery, University of California at Los Angeles, Los Angeles, CA †Department of Orthopaedic Surgery, Osaka City University, Osaka, Japan ‡Department of Orthopaedic Surgery, University of Southern California at Los Angeles, Los Angeles, CA.
authors.forename: Shinji
authors.initials: S
authors.lastname: Takahashi
authors.forename: Elizabeth L
authors.initials: EL
authors.lastname: Lord
authors.forename: Tetsuo
authors.initials: T
authors.lastname: Hayashi
authors.forename: Jeremiah R
authors.initials: JR
authors.lastname: Cohen
authors.forename: Lifeng
authors.initials: L
authors.lastname: Lao
authors.forename: Qingqiang
authors.initials: Q
authors.lastname: Yao
authors.forename: Akinobu
authors.initials: A
authors.lastname: Suzuki
authors.forename: Hiroaki
authors.initials: H
authors.lastname: Nakamura
authors.forename: Jeffrey C
authors.initials: JC
authors.lastname: Wang
mesh_terms: D000328:Adult; D001696:Biomechanical Phenomena; D003710:Demography; D004388:Dura Mater / Q000000981:diagnostic imaging* / Q000473:pathology*; D005260:Female; D006801:Humans; D007403:Intervertebral Disc / Q000000981:diagnostic imaging / Q000473:pathology; D008159:Lumbar Vertebrae / Q000000981:diagnostic imaging* / Q000473:pathology*; D008279:Magnetic Resonance Imaging; D008297:Male