title: MR signal in the sacroiliac joint space in spondyloarthritis: a new sign.
abstract: OBJECTIVE
  To determine the diagnostic value of MR signal within the sacroiliac (SI) joint space in spondyloarthritis (SpA).
  
  
  METHODS
  A retrospective analysis of MRIs of SI joints was performed in 363 patients, aged 16-45 years, clinically suspected of sacroiliitis. Intra-articular SI joint MR signals were categorized as normal, high T1 signal, fluid signal, ankylosis or vacuum phenomenon (VP). These MRI findings were correlated with the final diagnosis, according to the ASAS criteria. Sensitivity, specificity, and positive and negative likelihood ratios (LR) and predictive values were calculated.
  
  
  RESULTS
  Presence of intra-articular high T1 signal, fluid signal and ankylosis had a specificity of 95.8 %, 95.3 % and 99.5 % for SpA. High T1 signal, fluid signal and ankylosis were present in 38.4 %, 19.2 % and 17.9 % of SpA patients and in 4.2 %, 4.7 % and 0.5 % of patients without SpA, resulting in LR+ of 9.0, 4.1 and 37.9, respectively. VP was present in 13.2 % of SpA patients and in 20.8 % of patients without SpA, resulting in an LR+ of 0.6.
  
  
  CONCLUSIONS
  Presence of high T1 signal, fluid signal and ankylosis within the SI joint on MRI have high specificity for SpA. High T1 signal is the most sensitive MRI feature within the SI joint for SpA.
  
  
  CONCLUSIONS
  • MRI of the SI joints is typically obtained for diagnosis of spondyloarthritis. • The MR signal within the SI joint itself reflects features of spondyloarthritis. • Intra-articular high T1 signal, fluid signal and ankylosis are seen in spondyloarthritis. • The vacuum phenomenon makes spondyloarthritis less likely.
authors.affiliation: Department of Radiology and Medical Imaging, Ghent University Hospital, De Pintelaan 185, B-9000, Gent, Belgium. Frederiek.Laloo@UGent.be.
authors.forename: Frederiek
authors.initials: F
authors.lastname: Laloo
authors.affiliation: Department of Radiology and Medical Imaging, Ghent University Hospital, De Pintelaan 185, B-9000, Gent, Belgium.
authors.forename: N
authors.initials: N
authors.lastname: Herregods
authors.affiliation: Department of Rheumatology, Ghent University Hospital, De Pintelaan 185, B-9000, Gent, Belgium.
authors.forename: G
authors.initials: G
authors.lastname: Varkas
authors.affiliation: Department of Radiology & Diagnostic Imaging, University of Alberta Hospital, 8440-112 Street, Edmonton, T6G 2B7, Alberta, Canada.
authors.forename: J L
authors.initials: JL
authors.lastname: Jaremko
authors.affiliation: Rheumazentrum Ruhrgebiet, Ruhr-University Bochum, Claudiusstr. 45, D-44649, Herne, Germany.
authors.forename: X
authors.initials: X
authors.lastname: Baraliakos
authors.affiliation: Department of Rheumatology, Ghent University Hospital, De Pintelaan 185, B-9000, Gent, Belgium.
authors.forename: D
authors.initials: D
authors.lastname: Elewaut
authors.affiliation: Department of Rheumatology, Ghent University Hospital, De Pintelaan 185, B-9000, Gent, Belgium.
authors.forename: F
authors.initials: F
authors.lastname: Van den Bosch
authors.affiliation: Department of Radiology and Medical Imaging, Ghent University Hospital, De Pintelaan 185, B-9000, Gent, Belgium.
authors.forename: K
authors.initials: K
authors.lastname: Verstraete
authors.affiliation: Department of Radiology and Medical Imaging, Ghent University Hospital, De Pintelaan 185, B-9000, Gent, Belgium.
authors.forename: L
authors.initials: L
authors.lastname: Jans
mesh_terms: D000293:Adolescent; D000328:Adult; D000844:Ankylosis / Q000000981:diagnostic imaging; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods; D008297:Male; D008875:Middle Aged; D012189:Retrospective Studies; D012446:Sacroiliac Joint / Q000000981:diagnostic imaging*; D058566:Sacroiliitis / Q000000981:diagnostic imaging*; D012680:Sensitivity and Specificity; D025241:Spondylarthritis / Q000000981:diagnostic imaging*; D055815:Young Adult
keywords: Ankylosis; MRI; Sacroiliac joint; Sacroiliitis; Spondyloarthritis