POS1417 INTEROSSEOUS TENDON INFLAMMATION IN THE HANDS: A NOVEL FEATURE OF DEVELOPING RHEUMATOID ARTHRITIS? RESULTS FROM A LARGE MRI STUDY IN CLINICALLY SUSPECT ARTHRALGIA

Abstract

BackgroundInflammation around the tendons of the hand interosseous muscles (interosseous tendon inflammation; ITI) on MRI was recently reported in rheumatoid arthritis (RA) patients and in ACPA-positive individuals with musculoskeletal symptoms. We therefore hypothesized that ITI is an early RA-feature that precedes clinical arthritis.ObjectivesTo examine this we assessed the frequency of ITI in clinically suspect arthralgia (CSA) patients and compared this to the frequency in the general population. Additionally we investigated the relation between ITI and other locally inflamed tissues (synovitis/tenosynovitis/osteitis) in MCP-joins of CSA patients as well as the association with future arthritis development.Methods667 consecutive patients presenting with CSA and 193 symptom-free controls from the general population underwent contrast-enhanced hand-MRI. MRIs were evaluated for ITI and for synovitis/tenosynovitis/osteitis, using the rheumatoid arthritis MRI scoring system (RAMRIS). CSA patients were followed for clinical arthritis development (median follow-up 25 months). Logistic and Cox-regression were used. ACPA-stratification was performed. To gain a better understanding of the anatomical relationships, 3D MRI-reconstruction of the interosseous and lumbrical muscles and tendons was performed in a patient with ITI.ResultsAt presentation, 10% of CSA patients had ITI, compared to 1% of symptom-free controls (p<0.001). ITI was more frequent in ACPA-positive than ACPA-negative CSA (27% versus 7%; p<0.001). 72% of patients with ITI also had synovitis and/or tenosynovitis at the MCPs (37% synovitis; 7% tenosynovitis; 27% both synovitis and tenosynovitis). Also in multivariable analyses, adjusted for simultaneous presence of synovitis/tenosynovitis/osteitis, ITI was more likely if synovitis (OR 2.2 (95%CI 1.2-4.2)) or tenosynovitis (9.7 (5.5-17.0)) was present at MCPs. The 3D MRI-reconstruction indicated that ITI is continuous with MCP flexor tenosynovitis (Figure 1). CSA patients with ITI developed arthritis more frequent than those without (HR 4.5 (2.8-7.2)); this relation was stronger in ACPA-negative (3.9 (1.9-7.9)) than ACPA-positive CSA (1.8 (0.9-3.4)).ConclusionITI is present in CSA and precedes clinical arthritis, suggesting that this peritendinous inflammation is an early RA-feature.AcknowledgementsWe thank G. Kracht for his assistance with preparing the example MR-image.Disclosure of InterestsNone declared