title: Acute osteoporotic and neoplastic vertebral compression fractures: fluid sign at MR imaging.
abstract: OBJECTIVE
  To evaluate the occurrence, location, and shape of the fluid sign in acute osteoporotic and neoplastic vertebral compression fractures at magnetic resonance (MR) imaging.
  
  
  METHODS
  The study group comprised 87 consecutive patients with acute vertebral compression fractures due to osteoporotic (n = 52) or neoplastic (n = 35) infiltration. The MR imaging protocol included nonenhanced T1-weighted spin-echo and short inversion time inversion-recovery sequences and a 1.5-T system. Readers blinded to the outcome documented the occurrence, shape, and location of the fluid sign with consensus. The fluid sign was correlated with the cause, age, and severity of the fracture. The diagnosis was confirmed with surgery, follow-up MR imaging, clinical follow-up, or unequivocal imaging findings. Wilcoxon and chi(2) tests were used to assess significance.
  
  
  RESULTS
  In fractured vertebral bodies, the fluid sign was adjacent to the fractured end plates and exhibited signal intensity isointense to that of cerebrospinal fluid. The fluid sign was linear (n = 16), triangular (n = 5), or focal (n = 2) and was significantly associated with osteoporotic fractures (21 [40%] of 52; P <.001). The fluid sign occurred in two (6%) of 35 neoplastic compression fractures. Histologic examination demonstrated osteonecrosis, edema, and fibrosis at the site of the fluid sign. There was a tendency toward older fractures exhibiting the fluid sign, but this relationship was not significant (P >.05). In osteoporotic fractures, the fluid sign was significantly associated with fracture severity (P <.05).
  
  
  CONCLUSIONS
  The fluid sign is featured in acute vertebral compression fractures that show bone marrow edema. It can be an additional sign of osteoporosis and rarely occurs in metastatic fractures.
authors.affiliation: Departments of Clinical Radiology, University of Munich-Grosshadern, Marchioninistrasse 15, 81377 Munich, Germany. andrea.baur@ikra.med.uni-muenchen.de
authors.forename: Andrea
authors.initials: A
authors.lastname: Baur
authors.forename: Axel
authors.initials: A
authors.lastname: Stäbler
authors.forename: Susanne
authors.initials: S
authors.lastname: Arbogast
authors.forename: Hans Roland
authors.initials: HR
authors.lastname: Duerr
authors.forename: Reiner
authors.initials: R
authors.lastname: Bartl
authors.forename: Maximilian
authors.initials: M
authors.lastname: Reiser
mesh_terms: D000368:Aged; D005260:Female; D005598:Fractures, Spontaneous / Q000175:diagnosis* / Q000209:etiology; D006801:Humans; D008159:Lumbar Vertebrae; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D009369:Neoplasms / Q000150:complications*; D010024:Osteoporosis / Q000150:complications*; D016103:Spinal Fractures / Q000175:diagnosis* / Q000209:etiology; D013904:Thoracic Vertebrae