title: Dynamic changes in spinal cord compression by cervical ossification of the posterior longitudinal ligament evaluated by kinematic computed tomography myelography.
abstract: METHODS
  A prospective clinical study.
  
  
  OBJECTIVE
  To investigate the dynamic causative factor in the pathogenesis of myelopathy in patients with cervical ossification of the posterior longitudinal ligament (OPLL) using kinematic computed tomography (CT) myelography.
  
  
  BACKGROUND
  Kinematic CT myelography is useful for dynamically evaluating the cervical spine with high-resolution images, particularly in bony compressive lesions. However, no studies have evaluated the dynamic factors in patients with OPLL using kinematic CT myelography.
  
  
  METHODS
  From 2008 to 2013, 51 consecutive patients with OPLL who presented with myelopathy were prospectively enrolled in this study. The patients were examined with kinematic (flexion-extension) CT myelography using a multidetector CT scanner. The range of motion at C2-C7 from flexion to extension was measured in the sagittal view. The segmental range of motion, anterior-posterior diameter and cross-sectional area (CSA) of the spinal cord were measured at the level where the spinal cord was most compressed by OPLL.
  
  
  RESULTS
  The neurological condition of the patients evaluated by Japanese Orthopaedic Association scores were 10.8 ± 2.4 points. The mean range of motion at C2-C7 and at the most compressed segment were 23.1 ± 11.7 and 7.0 ± 4.4°, respectively. Both the anterior-posterior diameter and the CSA at the most compressed levels were significantly decreased during neck extension compared with flexion. Interestingly, the anterior-posterior diameter and the CSA were decreased during neck flexion in 13.7% (7/51) of the patients. All 7 of these patients had massive OPLL with an occupying rate 60% or more. The dynamic change rate of CSA (flexion/extension) was significantly smaller in patients with an OPLL occupying rate 60% or more compared with patients with an occupying rate less than 60%.
  
  
  CONCLUSIONS
  Although spinal cord compression was increased during neck extension in most of the patients, greater levels of compression could be placed on the spinal cord during neck flexion when the patients had OPLL with a high occupying rate.
  
  
  METHODS
  4.
authors.affiliation: *Section of Orthopaedic and Spinal Surgery, Graduate School and †Section of Regenerative Therapeutics for Spine and Spinal Cord, Graduate School, Tokyo Medical and Dental University, Bunkyo-ku, Tokyo, Japan; and ‡Global Center of Excellence (GCOE) Program for International Research Center for Molecular Science in Tooth and Bone Disease, Tokyo Medical and Dental University, Kanda-Surugadai, Chiyoda-ku, Tokyo, Japan.
authors.forename: Toshitaka
authors.initials: T
authors.lastname: Yoshii
authors.forename: Tsuyoshi
authors.initials: T
authors.lastname: Yamada
authors.forename: Takashi
authors.initials: T
authors.lastname: Hirai
authors.forename: Takashi
authors.initials: T
authors.lastname: Taniyama
authors.forename: Tsuyoshi
authors.initials: T
authors.lastname: Kato
authors.forename: Mitsuhiro
authors.initials: M
authors.lastname: Enomoto
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Inose
authors.forename: Satoshi
authors.initials: S
authors.lastname: Sumiya
authors.forename: Shigenori
authors.initials: S
authors.lastname: Kawabata
authors.forename: Kenichi
authors.initials: K
authors.lastname: Shinomiya
authors.forename: Atsushi
authors.initials: A
authors.lastname: Okawa
mesh_terms: D000328:Adult; D000368:Aged; D001696:Biomechanical Phenomena; D002574:Cervical Vertebrae / Q000000981:diagnostic imaging*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009192:Myelography / Q000379:methods*; D017887:Ossification of Posterior Longitudinal Ligament / Q000000981:diagnostic imaging* / Q000453:epidemiology; D011446:Prospective Studies; D013117:Spinal Cord Compression / Q000000981:diagnostic imaging* / Q000453:epidemiology; D014057:Tomography, X-Ray Computed / Q000379:methods*