title: Vertebral osteonecrosis: MR imaging findings and related changes on adjacent levels.
abstract: OBJECTIVE
  No prior report has comprehensively discussed the intravertebral vacuum cleft sign and the fluid sign on MR images of vertebral osteonecrosis. The purpose of this study was to investigate MR images of osteonecrotic vertebral bodies and adjacent intervertebral disks and vertebral bodies.
  
  
  METHODS
  We retrospectively reviewed MR images of patients with vertebral osteonecrosis. Affected vertebral bodies with osteonecrosis were defined as an avascular area (nonenhanced area on enhanced T1-weighted images) with collections of intravertebral fluid (hyperintense signal on T2-weighted images), air (signal void on all images), or both. The degree of vertebral collapse was classified as mild (>50%) or severe (<50%) preserved vertebral height. Changes in adjacent intervertebral disks or vertebral bodies 2 above and 2 below the affected vertebrae were compared.
  
  
  RESULTS
  We enrolled 112 patients (30 men, 82 women; 121 vertebral bodies) in our study. Intravertebral air alone was observed in 48 involved levels (39.7%), intravertebral fluid alone was found in 47 (38.8%), and both coexisted in 26 (21.5%). Degree of vertebral collapse in affected vertebral bodies significantly differed with presence of air or fluid (P < .05). Vertebral compression fractures adjacent to the affected vertebral bodies were more common in those with intravertebral air alone than in those with intravertebral fluid alone (P < .05).
  
  
  CONCLUSIONS
  Vertebral collapse was more advanced and adjacent vertebral compression fractures were more frequent in patients with intravertebral air than in those with intravertebral fluid.
authors.affiliation: Department of Medical Imaging and Radiology, National Taiwan University Hospital, Taipei, Taiwan.
authors.forename: C-W
authors.initials: CW
authors.lastname: Yu
authors.forename: C-Y
authors.initials: CY
authors.lastname: Hsu
authors.forename: T T-F
authors.initials: TT
authors.lastname: Shih
authors.forename: B-B
authors.initials: BB
authors.lastname: Chen
authors.forename: C-J
authors.initials: CJ
authors.lastname: Fu
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D000388:Air; D004487:Edema / Q000175:diagnosis; D005260:Female; D050815:Fractures, Compression / Q000175:diagnosis; D005598:Fractures, Spontaneous / Q000175:diagnosis*; D006801:Humans; D007403:Intervertebral Disc / Q000473:pathology; D008159:Lumbar Vertebrae / Q000473:pathology; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D015588:Observer Variation; D010020:Osteonecrosis / Q000175:diagnosis*; D012189:Retrospective Studies; D012680:Sensitivity and Specificity; D013122:Spinal Diseases / Q000175:diagnosis*; D016103:Spinal Fractures / Q000175:diagnosis; D013904:Thoracic Vertebrae / Q000473:pathology