title: Evaluation of ossification of the posterior longitudinal ligament by three-dimensional computed tomography and magnetic resonance imaging.
abstract: BACKGROUND
  Detection of ossification of the posterior longitudinal ligament (OPLL) of lesions by lateral radiography is sometimes difficult because the lesions are small. Three-dimensional computed tomography (3D CT) imaging has made it possible to detect lesions not been seen by lateral radiography.
  
  
  OBJECTIVE
  To evaluate the use of 3D CT in visualizing and classifying OPLL, and the added value of magnetic resonance imaging (MRI) in determining spinal cord compression.
  
  
  METHODS
  Prospective case study in an academic department of orthopedic surgery.
  
  
  METHODS
  Patients with OPLL diagnosed by lateral radiography of the cervical spine from April 2006 to March 2007 were identified.
  
  
  METHODS
  Ossification of the posterior longitudinal ligament visualized lateral radiography was classified according to the existing scheme as continuous, segmental, mixed, or other type. Ossification of the posterior longitudinal ligament visualized by 3D CT was organized into a classification system comprising flat, irregular, or localized types and were compared with the lateral radiographic images. Magnetic resonance imaging was done to determine the extent of spinal cord compression.
  
  
  RESULTS
  All 55 patients (35 men and 20 women; median age, 66 years) with OPLL were enrolled. Of these, 41 (75%) had a type of OPLL as visualized by 3D CT that corresponded with only one type of OPLL as visualized by lateral radiography. In 39 (71%) of 55, the areas of the ossified lesions visualized by 3D CT were the same as those visualized by lateral radiography. In the other 16, the lesions were either too small or too unclear to be visualized by lateral radiography. In all cases, 3D CT imaging showed that the transverse width of OPLL was within the bilateral Luschka joints, which was not noted by lateral radiography. In 13 of the 14 subjects who underwent MRI, spinal cord compression was noted at the superior or inferior edges of the ossified lesions that had been seen by 3D CT.
  
  
  CONCLUSIONS
  Three-dimensional computed tomography visualization of OPLL provided the basis of a classification system, superior to lateral radiography, and provided new information about OPLL. Combining 3D CT with MRI might be useful to provide details about spinal cord compression in OPLL.
authors.affiliation: Department of Orthopaedic Surgery, Faculty of Medicine, University of Toyama, 2630 Sugitani, Toyama 930-0194, Japan. zenji@med.u-toyama.ac.jp
authors.forename: Yoshiharu
authors.initials: Y
authors.lastname: Kawaguchi
authors.forename: Aya
authors.initials: A
authors.lastname: Urushisaki
authors.forename: Shoji
authors.initials: S
authors.lastname: Seki
authors.forename: Takeshi
authors.initials: T
authors.lastname: Hori
authors.forename: Yumiko
authors.initials: Y
authors.lastname: Asanuma
authors.forename: Tomoatsu
authors.initials: T
authors.lastname: Kimura
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D017887:Ossification of Posterior Longitudinal Ligament / Q000175:diagnosis* / Q000000981:diagnostic imaging / Q000473:pathology; D011446:Prospective Studies; D013117:Spinal Cord Compression / Q000175:diagnosis* / Q000000981:diagnostic imaging / Q000473:pathology; D014057:Tomography, X-Ray Computed