Clinical importance of inflammatory facet joints of the spine in ankylosing spondylitis: a magnetic resonance imaging study.
OBJECTIVE
The aims of this study were to assess the reliability of a novel magnetic resonance imaging (MRI) scoring system for inflammatory lesions of facet joints and to clarify the clinical significance of facet joint inflammation in ankylosing spondylitis (AS).


METHODS
A total of 53 AS patients (45 males, 84.9%) were assessed for active inflammatory lesions involving the facet joints, as indicated by bone marrow oedema, at 23 discovertebral units (DVUs) between C2 and S1 using a novel scale, the AS Activity of the Facet joint (ASAFacet). The reliability of the ASAFacet was evaluated using intraclass correlation coefficients (ICCs) and Bland-Altman plots.


RESULTS
ICC values for the ASAFacet scores were 0.857 [95% confidence interval (CI) 0.741-0.919] for inter-observer and 0.941 (95% CI 0.873-0.969) for intra-observer reliability. Inflammatory activity scores in facet joints were evenly distributed at all spine levels (p = 0.294 for ASAFacet), whereas vertebral body inflammation was more prominent in the thoracic spine than in the cervical and lumbar spine [p < 0.001 for the AS spine MRI activity (ASspiMRI-a) score, p = 0.002 for the Berlin method, and p < 0.001 for the Spondyloarthritis Research Consortium of Canada (SPARCC) MRI index]. ASAFacet scores were closely associated with erythrocyte sediment rate (ESR) and C-reactive protein (CRP) levels (p < 0.05, respectively). Patients with peripheral arthritis had fewer lesions involving the vertebral bodies or facet joints than patients without peripheral arthritis (p < 0.001 for the four different MRI activity indexes).


CONCLUSIONS
This study suggests that recognition of facet joint inflammation has the potential to contribute to our understanding of clinical outcomes in AS.
a Department of Radiology , Hanyang University Hospital for Rheumatic Diseases , Seoul , South Korea.
S
S
Lee
a Department of Radiology , Hanyang University Hospital for Rheumatic Diseases , Seoul , South Korea.
J Y
JY
Lee
b Department of Preventive Medicine , Catholic University of Daegu School of Medicine , Daegu , South Korea.
J H
JH
Hwang
c Hanyang University Hospital for Rheumatic Diseases , Seoul , South Korea.
J H
JH
Shin
c Hanyang University Hospital for Rheumatic Diseases , Seoul , South Korea.
T-H
TH
Kim
d Division of Rheumatology, Department of Internal Medicine, Arthritis and Autoimmunity Research Centre , Catholic University of Daegu School of Medicine , Daegu , South Korea.
S-K
SK
Kim
D000328:Adult; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D012189:Retrospective Studies; D012720:Severity of Illness Index; D013167:Spondylitis, Ankylosing / Q000000981:diagnostic imaging*; D021801:Zygapophyseal Joint / Q000000981:diagnostic imaging*