OP0132 HOW ACCURATE IS PHYSICAL JOINT EXAMINATION OF THE MTP-JOINTS, AND WHAT CAN WE LEARN FROM ADDITIONAL MAGNETIC RESONANCE IMAGING ON FOREFOOT INVOLVEMENT IN EARLY ARTHRITIS?

Background Magnetic resonance imaging (MRI) is known to be more sensitive than physical examination in detecting inflammation, and has predominantly been studied in metacarpophalangeal-(MCP) and wrist-joints. Data on the concordance and discordance of physical examination and MRI-detected inflammation of metatarsophalangeal-(MTP)joints is scarce, which is surprising as physical examination of these joints is generally considered more challenging than of MCP-joints. Objectives We aimed to study the concordance and discordance of arthritis upon physical examination with MRI-detected inflammation of MTP-joints. Analyses on MCP-joints were included for comparison. Methods 1764 MTP(2-5)-joints and 1764 MCP(2-5)-joints of 441 consecutive patients presenting with early inflammatory arthritis (36% RA, 64% other inflammatory arthritides) underwent physical examination (PE) of joint swelling and 1.5T contrast-enhanced MRI of unilateral MCP- and MTP-joints. MRI-detected synovitis and bone marrow oedema were scored according to the RA MRI score (RAMRIS), and tenosynovitis according to Haavardsholm by two experienced readers (scores ranged 0-3). Analyses were done on joint level and joints were grouped as PE+MRI+, PE–MRI–, PE+MRI– and PE–MRI+. MRI-positivity required the presence of the same MRI-inflammatory feature on joint level that was scored by both readers≥1. In addition, to be classified as PE+MRI–, the joints required to have clinical swelling as objectified by two independent observers. After categorisation, the MRIs of the joints that were PE+MRI– were further studied by two other, independent observers among whom an experienced musculoskeletal radiologist, to investigate the presence of contrast-enhancement that was not scored according to RAMRIS guidelines. Results Physical examination of joints and MRI were concordant in 79% of MTP-joints (6% PE+MRI+, 74% PE–MRI–). For the MCP-joints this was 71% (15% and 56% respectively). Next discordance was studied. Subclinical joint inflammation (PE–MRI+) was present in 14% (n=248) of MTP-joints. This was less frequent than in MCP-joints, where subclinical inflammation was present in 27% joints (n=465, p Subsequently, the MRIs of the joints that were clinically inflamed and scored negative according to RAMRIS were studied for other MRI-abnormalities. Out of the 78 MTP-joints that were PE+MRI–, 54% (n=42) showed no MRI abnormalities, whereas in 46% (n=36) extra-articular contrast-enhanced lesions were observed that were predominantly identified as peri-arthritis and intermetatarsal bursitis. Within this category, extra articular inflammation was more prevalent in RA than in other inflammatory arthritides (58% vs 26%, p=0.005). At the MCPs no extra-articular inflammation was found. Conclusion Joint examination and MRI were mostly concordant in MTP- and MCP-joints. In MTP-joints MRI-detected subclinical joint inflammation was infrequent (14%), especially when compared to MCP-joints (27%). Clinical joint swelling without MRI-detected joint inflammation according to RAMRIS was also infrequent (5% of MTP-joints) and in part caused by extra-articular inflammation such as intermetatarsal bursitis. Further detailed imaging studies are needed to determine if extra-articular inflammation at the level of MTP-joints, with or without concomitant intra-articular inflammation, is a novel finding that is characteristic for early RA. Disclosure of Interests:  Yousra Dakkak: None declared, Aleid Boer: None declared, Debbie Boeters: None declared, 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., Annette van der Helm - van Mil Grant/research support from: The research leading to these results has received funding from the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation programme (Starting grant, agreement No 714312) and from the Dutch Arthritis Foundation. The funding source had no role in the design and conduct of the study.