POS0021 INTERMETATARSAL BURSITIS, A NOVEL FEATURE OF JUXTA-ARTICULAR INFLAMMATION IN EARLY RHEUMATOID ARTHRITIS: RESULTS FROM A LONGITUDINAL MRI-STUDY

Background: Rheumatoid arthritis (RA) is characterised by inflammation of the synovial lining. In addition to synovitis, tendon sheaths small hand and foot joints are also frequently inflamed. This results in tenosynovitis, which often missed at clinical evaluation early RA but visible on imaging, such as MRI. A third anatomical structure surrounded a lining formed intermetatarsal bursae forefeet. Inflammation these (intermetatarsal bursitis; IMB) was recently identified MRI-studies shown be specific for RA.[1] suggests that IMB feature RA. Objectives: We hypothesised if indeed an RA-feature, then (1) diagnosis its presence associates with other measures local (synovitis, tenosynovitis osteitis) (2) it responds DMARD therapy similarly inflammatory measures. These hypotheses were tested comprehensive MRI-study. Methods: 157 consecutive patients underwent unilateral contrast-enhanced 1.5T MRI forefoot diagnosis. MRIs evaluated osteitis line scoring system (summed RAMRIS-inflammation). 4, 12 24 months size IMB-lesions who had baseline received DMARD-therapy. Logistic regression used analyses patient-level; generalised estimating equations bursa-level analyses. Stratification ACPA performed. Results: 69% ≥1 IMB. multivariable bursa-level, independently associated synovitis (OR 1.69 (95%CI 1.12–2.57) 2.83 (1.80–4.44), respectively), not osteitis. On patient-level, most strongly 2.92 (1.62–5.24)). During treatment DMARDs, average decreased (Figure 1). decrease RAMRIS-inflammation scores; Within ACPA-positive ACPA-negative similar obtained. Conclusion: particularly accompanies tendon-sheaths, both regarding simultaneous occurrence treatment-response. findings suggest represents juxta-articular hallmark References: [1]Dakkak YJ et al. Increased frequency submetatarsal bursitis rheumatoid arthritis: large case-controlled study. Arthritis Res Ther 22, 277 (2020). Disclosure Interests: None declared.