SAT0559 INCREASED FREQUENCY OF INTER- AND SUBMETATARSAL BURSITIS AND MORTON’S NEUROMA IN RHEUMATOID ARTHRITIS: RESULTS OF A LARGE CASE-CONTROLLED MRI STUDY OF FOREFEET IN PATIENTS WITH EARLY ARTHRITIS AND HEALTHY CONTROLS

Abstract

Background:The forefoot is a preferential location for tendon and joint inflammation in rheumatoid arthritis (RA). Some imaging studies suggested that intermetatarsal and submetatarsal pathology (such as bursitis and Morton’s neuroma) are also involved in RA, but these studies were small and its association was not thoroughly explored.Objectives:To determine whether intermetatarsal bursitis (IMB), Morton’s neuroma (MN) and submetatarsal bursitis (SMB) occur more often in early RA, compared to patients with other early arthritides and healthy controls. Contrast-enhancement in the subcutis that has been described as diffuse submetatarsal alterations (DSMA) were also included.Methods:In this cross-sectional cohort-study, consecutive patients with RA, other arthritides and healthy controls underwent MRI of unilateral forefoot. Two readers, a trained PhD-student an experienced MSK-radiologist, scored IMB, MN, SMB and DSMA in consensus, and measured transverse and dorsoplantar diameters of IMB, MN and SMB. Logistic regression models determined their association with RA, and test characteristics for RA were calculated. Lesion-sizes were plotted.Results:634 participants underwent MRI: 157 consecutive patients with RA (109 women; age 59±11SD), 284 with other early arthritides (158 women; age 56±17SD), and 193 healthy controls (136 women; age 50±16SD). Univariably, IMB, MN and SMB were more prevalent in RA (all P<0.001), DSMA was not (P=0.16). Multivariably, MB, SMB and MN were all associated with RA independent of each other (P<0.016). IMB was most frequent (sensitivity 69%), followed by SBM and MN (25% and 19%), specificity was high (70%, 96%, 94% respectively compared to other arthritides and 84%, 99% and 97% compared to healthy controls).Although IMB, MN and SNB were more frequent in RA, the lesion-size was mainly similar in all groups. For MN a dorsoplantar diameter >6mm or transverse diameter >5mm was highly specific (specificity 100% compared to healthy controls), however it was infrequent (sensitivity 12% and 13%, respectively). For IMB and SMB no cut-off size could be distinguished with high specificity.Conclusion:Intermetatarsal bursitis, Morton’s neuroma and submetatarsal bursitis are increased prevalent in early RA and could be considered as disease features.Disclosure of Interests:None declared