title: HIZ's relation to axial load and low back pain: investigated with axial loaded MRI and pressure controlled discography.
abstract: OBJECTIVE
  The aims were to investigate if the detection of high-intensity zones (HIZ) is affected by axial load, and to study the correlation between HIZ and discogenic pain provoked with pressure controlled discography (PCD).
  
  
  METHODS
  41 consecutive patients with chronic low back pain, referred for discography, were included. Each patient underwent PCD, CT, MRI, and axial loaded MRI (alMRI) within 24 h. 35 patients completed all MRI sequences (140 discs). The detection of HIZ was compared between conventional MRI and alMRI. PCD was performed in 119 of the discs examined at MRI. Provoked pain at PCD was classified into four categories (none/unfamiliar/similar/exact), with the patients' daily pain as reference, and correlated with presence of HIZ.
  
  
  RESULTS
  AlMRI did not affect the detection of HIZ compared with conventional MRI. No significant correlation between HIZ and the 4-graded pain response at discography was found (p = 0.34), neither when combining similarly/exactly reproduced pain (p = 0.08). The sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) of HIZ in detecting discs with exactly reproduced pain were 49, 69, 39 and 76 %. When combining similarly/exactly reproduced pain, PPV was higher but still only 70 %.
  
  
  CONCLUSIONS
  The detection of HIZ was not influenced by axial load. With strict PCD, discogenic pain can neither be confirmed when having HIZ (PPV 39 %) nor ruled out in discs without HIZ (NPV 76 %). Larger PCD studies including quantification of HIZ at conventional and alMRI are needed, before any dynamic component affected by axial load can be ruled out completely.
authors.affiliation: Department of Radiology, Sahlgrenska University Hospital, Gothenburg, Sweden. hanna.hebelka@vgregion.se
authors.forename: Hanna
authors.initials: H
authors.lastname: Hebelka
authors.forename: Hebelka
authors.initials: H
authors.lastname: Hanna
authors.forename: Tommy
authors.initials: T
authors.lastname: Hansson
authors.forename: Hansson
authors.initials: H
authors.lastname: Tommy
mesh_terms: D000328:Adult; D005260:Female; D006801:Humans; D017116:Low Back Pain / Q000000981:diagnostic imaging / Q000473:pathology* / Q000503:physiopathology; D008159:Lumbar Vertebrae / Q000000981:diagnostic imaging / Q000473:pathology* / Q000503:physiopathology; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008875:Middle Aged; D011237:Predictive Value of Tests; D012189:Retrospective Studies; D012680:Sensitivity and Specificity; D014057:Tomography, X-Ray Computed; D016474:Weight-Bearing / Q000502:physiology*