title: Increased Facet Fluid Predicts Dynamic Changes in the Dural Sac Size on Axial-Loaded MRI in Patients with Lumbar Spinal Canal Stenosis.
abstract: OBJECTIVE
  Axial-loaded MR imaging, which simulates the spinal canal in a standing position, demonstrates reductions of the dural sac cross-sectional area in patients with lumbar spinal canal stenosis. However, there has been no useful conventional MR imaging finding for predicting a reduction in the dural sac cross-sectional area on axial-loaded MR imaging. Previous studies have shown that increased facet fluid is associated with the spinal instability detected during positional changes. The purpose of this study was to analyze the correlations between facet fluid and dynamic changes in the dural sac cross-sectional area on axial-loaded MR imaging.
  
  
  METHODS
  In 93 patients with lumbar spinal canal stenosis, the dural sac cross-sectional area was measured by using axial images of conventional and axial-loaded MR imaging. Changes in the dural sac cross-sectional area induced by axial loading were calculated. The correlation between the facet fluid width measured on conventional MR imaging and the change in dural sac cross-sectional area was analyzed. The change in the dural sac cross-sectional area was compared between the intervertebral levels with and without the facet fluid width that was over the cutoff value determined in this study.
  
  
  RESULTS
  The dural sac cross-sectional area was significantly smaller on axial-loaded MR imaging than on conventional MR imaging. The facet fluid width significantly correlated with the change in the dural sac cross-sectional area (r = 0.73, P < .001). The change in the dural sac cross-sectional area at the intervertebral level with the facet fluid width over the cutoff value was significantly greater than that at the other level.
  
  
  CONCLUSIONS
  The increased facet fluid on conventional MR imaging is highly predictive of the dynamic reduction of dural sac cross-sectional area detected on axial-loaded MR imaging in the clinical assessment of lumbar spinal canal stenosis.
authors.affiliation: From the Department of Orthopedic Surgery (H.K., H.O., T.A., E.I.), Tohoku University School of Medicine, Sendai, Japan kanno-h@isis.ocn.ne.jp.
authors.forename: H
authors.identifier: http://orcid.org/0000-0003-1985-2257
authors.initials: H
authors.lastname: Kanno
authors.affiliation: From the Department of Orthopedic Surgery (H.K., H.O., T.A., E.I.), Tohoku University School of Medicine, Sendai, Japan.
authors.forename: H
authors.identifier: http://orcid.org/0000-0002-6991-0948
authors.initials: H
authors.lastname: Ozawa
authors.affiliation: Department of Orthopedic Surgery (Y.K., N.M.), Sendai Nishitaga National Hospital, Sendai, Japan.
authors.forename: Y
authors.identifier: http://orcid.org/0000-0002-4620-2420
authors.initials: Y
authors.lastname: Koizumi
authors.affiliation: Department of Orthopedic Surgery (Y.K., N.M.), Sendai Nishitaga National Hospital, Sendai, Japan.
authors.forename: N
authors.identifier: http://orcid.org/0000-0003-0601-385X
authors.initials: N
authors.lastname: Morozumi
authors.affiliation: From the Department of Orthopedic Surgery (H.K., H.O., T.A., E.I.), Tohoku University School of Medicine, Sendai, Japan.
authors.forename: T
authors.identifier: http://orcid.org/0000-0003-1571-5618
authors.initials: T
authors.lastname: Aizawa
authors.affiliation: From the Department of Orthopedic Surgery (H.K., H.O., T.A., E.I.), Tohoku University School of Medicine, Sendai, Japan.
authors.forename: E
authors.identifier: http://orcid.org/0000-0002-9859-6791
authors.initials: E
authors.lastname: Itoi
mesh_terms: D000368:Aged; D019412:Anatomy, Cross-Sectional; D001826:Body Fluids; D004388:Dura Mater / Q000000981:diagnostic imaging / Q000473:pathology*; D005260:Female; D006801:Humans; D007403:Intervertebral Disc / Q000000981:diagnostic imaging / Q000473:pathology; D055959:Intervertebral Disc Degeneration / Q000000981:diagnostic imaging / Q000453:epidemiology / Q000209:etiology; D008159:Lumbar Vertebrae / Q000000981:diagnostic imaging / Q000473:pathology*; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D011237:Predictive Value of Tests; D011446:Prospective Studies; D013130:Spinal Stenosis / Q000000981:diagnostic imaging / Q000473:pathology*; D013168:Spondylolisthesis / Q000000981:diagnostic imaging / Q000453:epidemiology / Q000209:etiology; D021801:Zygapophyseal Joint / Q000000981:diagnostic imaging / Q000473:pathology*