Background In rheumatoid arthritis (RA) patients, bone marrow edema (BME)-scores are associated with development of erosions. However, little is known on the course and outcome of BME at bone level. Therefore this study determined the association of BME and MRI-synovitis in the same bone longitudinally.

Objectives This study was aimed to determine the course of BME and MRI-synovitis at bone level. Furthermore the association between the course of BME and local synovitis and the development of erosions in the same bone was studied.

Methods 1,947 bones of MCP, wrist and MTP-joints of 59 patients presenting with rheumatoid or undifferentiated arthritis were studied using 1.5T MRI at baseline, after four and twelve months. Scanning and scoring of BME, synovitis and erosions were performed according to RAMRIS. The relation of the course of BME and synovitis to erosive progression at bone level during 1-year was evaluated.

Results Of the bones showing BME at baseline (n=203), BME persisted in 56%, disappeared in 39%, and disappeared-reappeared seldom (5%). Stratified analyses at baseline revealed that BME was associated with erosive progression, in presence and in absence of local synovitis (ORs 7.5 95%CI 3.8-14.9 and 6.9 95%CI 1.9-25.6). Local synovitis, however, was not associated with erosive progression (OR 2.0 95%CI 0.6-7.0 in presence of BME and 1.9 95%CI 0.8-4.1 in the absence of BME). In multivariable GEE-analyses, persistent BME was strongly associated with erosive progression (OR 60 95%CI 17-318), in contrast to persistent synovitis (OR 1.4 95%CI 0.4-5.3).

Conclusions BME frequently persists during the first year. Persistent BME was strongly associated with erosive progression in the same bone, independent of local synovitis. No independent association was observed for persistent synovitis. These findings are relevant for the comprehension on the development of erosions in RA.

Disclosure of Interest None declared