Ab0914 Prevalence of Posterior Segment Lumbar Enhancement on Mri in Patients With Axial Spondyloarthropathy, Low Back Pain and Healthy Volunteers: A Cross-Sectional Study

Background: Spinal and sacroiliac involvement is frequent in axial spondyloarthropathy (axSpA). MRI criteria defining structural and inflammatory lesions for axSpA have been clearly described. However, enhancement of posterior spinal ligaments and zygapophyseal joints may be observed in patients with back pain who undergo contrast-enhanced MRI of the lumbar spine but have no other signs of axSpA. The clinical significance of this enhancement remains to be defined. Objectives: To compare the prevalence of enhancement of the posterior lumbar spine elements on contrast-enhanced MRI in patients with axSpA, low back pain (LBP) and asymptomatic volunteers. Methods: This is a retrospective cross-sectional study including patients with axSpA (fulfilling ASAS 2010 criteria) followed in the rheumatology clinic, patients with LBP without features of axSpA and a prospective cohort of volunteers who underwent a clinically indicated contrast-enhanced MRI of the abdomen or pelvis, did not have back pain based on a questionnaire, and consented to an additional MRI sequence covering the lumbar spine. Two musculoskeletal radiologists (R1 and R2) reviewed MRI images blinded to patient clinical data. Anonymized contrast-enhanced sagittal fat-suppressed T1-weighted MRI images were independently analyzed. 40 anatomical structures, from L1 to S1 levels, were scored on every MRI, using a Likert scale (0-3): interspinous and supraspinous ligaments, articular recess, joint space, and periarticular soft tissues of bilateral zygapophyseal joints. A positive enhancement was defined as a score ≥2 for every structure. A global enhancement score was calculated by summing up all anatomical structures' scores, which were compared between groups. Results: MRI images of 248 patients (mean (SD) age: 51.9 (19.0)) were reviewed, including 77 patients with axSpA (39.6 (12.7)), 88 with LBP (61.5 (19.5)) and 83 volunteers (53.3 (17.0)). The prevalence of positive enhancement of the posterior elements (median global score [IQR]) for R1 was 62% (13 [8.0-20.2]) in the axSpA group, 72% (20 [12.0-28.5]) in the LBP group and 73% (26 [18-32]) in the volunteers group. For R1 and R2, the difference between groups was statistically significant (p<0.05). Interobserver agreement between R1 and R2 was fair (kappa=0.43, [0.37 to 0.49, 95%CI]). Conclusion: Enhancement of the posterior elements of the lumbar spine is a frequent finding on MRI of the lumbar spine, is not specific for axSpA, and is encountered in patients with non-inflammatory LBP as well as in asymptomatic volunteers. REFERENCES: NIL. Acknowledgements: NIL. Disclosure of Interests: Charbel Mourad: None declared, Tiago Borges Baptista: None declared, Alexandre Dumusc Novartis, Lilly, Abbvie, Pfizer, Abbvie, Patrick Omoumi: None declared.