SAT0528 DETECTION OF FACET JOINT ANKYLOSIS ON WHOLE SPINE LOW-DOSE CT IN RADIOGRAPHIC AXIAL SPONDYLOARTHRITIS: DATA FROM THE SENSITIVE IMAGING OF AXIAL SPONDYLOARTHRITIS (SIAS) COHORT
Authors: Rosalinde Stal, Floris A. van Gaalen, Alexandre Sepriano, Juergen Braun, Monique Reijnierse, Désirée van der Heijde, Xenofon Baraliakos
Journal: Annals of the Rheumatic Diseases (2019)

<h3>Background:</h3> In radiographic axial spondyloarthritis (r-axSpA), whole spine low-dose CT (ldCT) is superior in detecting syndesmophytes to conventional radiography (CR), which is limited to the lumbar and cervical spine. As facet joints are difficult to visualize on CR, CT has been used to study facet joint ankylosis in r-axSpA in parts of the spine. However, facet joints in the whole spine have never been studied. <h3>Objectives:</h3> To assess visibility and interreader reliability of facet joint ankylosis as detected by whole spine ldCT and to describe the prevalence of facet joint ankylosis in patients with r-axSpA. <h3>Methods:</h3> In an observational cohort, 60 r-axSpA patients with 1-18 syndesmophytes on CR and at least one inflammatory lesion on spinal MRI, underwent ldCT (approximately 4 mSV) of the whole spine. Images were assessed independently by two trained readers and left and right C2-C3 to L5-S1 facet joints were scored as ankylosis present (1) or absent (0). The percentages of missing joint scores per reader were calculated. Ankylosis scores were summed per patient for the whole spine and per segment and presented as mean scores per reader. Interreader reliability was assessed by calculating intraclass correlation coefficients (ICCs), two-way average, absolute agreement. <h3>Results:</h3> 60 r-axSpA patients were analyzed (mean age 47.7 years, 85% male, 80% HLA-B27+). Reader 1 had between 0% and 18.3% missings per joint, reader 2 had between 0% and 51.7% missings per joint (figure). Most missings occurred in the cervicothoracic junction for both readers and mostly at both left and right facet joints of the same level. Means (SD) of sum-scores for the whole spine and cervical, thoracic and lumbar segments for both readers as well as ICCs are presented in the Table. The lowest ICC was found in the cervical segment. After excluding facet joints with more than 15% missings (C5-C6 to T1-T2), ICCs were 0.93, 0.84 and 0.91 for the whole spine and cervical and thoracic segments, respectively. A striking finding is that while patients with &gt;18 syndesmophytes were excluded from our study, very high scores of ankylosis were reported, suggesting that facet joint ankylosis may occur without syndesmophytes at the same level. <h3>Conclusion:</h3> In patients with r-axSpA and at least one syndesmophyte, facet joint ankylosis was detected in all spinal segments. Facet joints around the cervicothoracic junction were difficult to score in a relatively high percentage of patients. The interreader reliability of the remaining levels was good to excellent. These results show that ldCT can be used to study facet joint ankylosis in axSpA in all segments of the spine except the cervicothoracic junction. <h3>Disclosure of Interests:</h3> Rosalinde Stal: None declared, Floris A. van Gaalen: None declared, Alexandre Sepriano: None declared, Juergen Braun Shareholder of: AbbVie, BMS, Celgene, Chugai, Merck, Novartis, Pfizer, UCB, Grant/research support from: AbbVie, BMS, Celgene, Chugai, Merck, Novartis, Pfizer, UCB, Grant/research support from: Abbott, Bristol Myers Squibb, Celgene, Celltrion, Chugai, Johnson &amp; Johnson, MSD, Novartis, Pfizer, Roche, UCB Pharma, Grant/research support from: AbbVie, BMS, Celgene, Chugai, Merck, Novartis, Pfizer, UCB, Grant/research support from: Abbvie (Abbott), Amgen, Baxter, Biogen, BMS, Boehringer, Celgene, Celltrion, Centocor, Chugai, Hexal, Janssen, Lilly, Medac, MSD (Schering-Plough), Mylan, Mundipharma, Novartis, Pfizer (Wyeth, Hospira), Roche, Sanofi-Aventis and UCB, Consultant for: Abbvie (Abbott), Amgen, Baxter, Biogen, BMS, Boehringer, Celgene, Celltrion, Centocor, Chugai, Hexal, Janssen, Lilly, Medac, MSD (Schering-Plough), Mylan, Mundipharma, Novartis, Pfizer (Wyeth, Hospira), Roche, Sanofi-Aventis and UCB, Consultant for: AbbVie, BMS, Celgene, Chugai, Merck, Novartis, Pfizer, UCB, Consultant for: Abbott, Bristol Myers Squibb, Celgene, Celltrion, Chugai, Johnson &amp; Johnson, MSD, Novartis, Pfizer, Roche, UCB Pharma, Speakers bureau: AbbVie, BMS, Celgene, Chugai, Merck, Novartis, Pfizer, UCB, Speakers bureau: Abbvie (Abbott), Amgen, Baxter, Biogen, BMS, Boehringer, Celgene, Celltrion, Centocor, Chugai, Hexal, Janssen, Lilly, Medac, MSD (Schering-Plough), Mylan, Mundipharma, Novartis, Pfizer (Wyeth, Hospira), Roche, Sanofi-Aventis and UCB, Speakers bureau: AbbVie, BMS, Celgene, Chugai, Merck, Novartis, Pfizer, UCB, Monique Reijnierse Grant/research support from: Funding from the Dutch Arthritis Foundation. The funding source had no role in the design and conduct of the study., Désirée van der Heijde Consultant for: AbbVie, Amgen, Astellas, AstraZeneca, Bristol-Myers Squibb, Boehringer Ingelheim, Celgene, Daiichi, Eli-Lilly, Galapagos, Gilead, GlaxoSmithKline, Janssen, Merck, Novartis, Pfizer, Regeneron, Roche, Sanofi, Takeda, Union Chimique Belge, Xenofon Baraliakos Grant/research support from: AbbVie, Boehringer Ingelheim, Bristol-Myers Squibb, Celgene, Centocor, Chugai, Janssen, MSD, Novartis, Pfizer Inc, Roche and UCB, Grant/research support from: AbbVie, Pfizer, Merck Sharp &amp; Dohme, UCB Pharma, Novartis, Consultant for: AbbVie, Bristol-Myers Squibb, Boehringer Ingelheim, Celgene, Chugai, Janssen Biologics, Novartis, Pfizer, UCB Pharma, Galapagos, Speakers bureau: AbbVie, Chugai, Janssen, Novartis, Pfizer, UCB Pharma