Background/Purpose: Ultrasound is sensitive for detection of inflammatory changes in patients with rheumatoid arthritis (RA). Intermetatarsal bursitis (IMB) may be detected by use of longitudinal dorsal scans between the metatarsophalangeal joints. The present objective was to explore the prevalence of IMB and its associations with subjective, clinical and laboratory assessments in established RA patients.

Methods: A total of 209 patients with RA (mean (SD) age 53 (13) years, disease duration 10 (9) years, 81% women, 79% anti-CCP positive) were included when initiating biological disease modifying antirheumatic drugs (bDMARD). The patients were assessed at baseline and after 1, 2, 3, 6 and 12 months with patient’s global disease activity VAS, clinical examination (assessor’s disease activity VAS, tender and swollen joint counts performed by a study nurse) and laboratory variables (ESR, CRP, anti-CCP and rheumatoid factor (RF)). Composite clinical scores (DAS28(ESR), CDAI and SDAI) were calculated. The presence of patient reported joint pain (PRJP) was assessed at joint level by use of a manikin (bilateral wrist, MCP1-5, PIP2-3, elbow, knee, ankle, MTP1-5). Each joint was scored 0-3 reflecting the level of spontaneous joint pain the last day. All ultrasound examinations (semi-quantitative scoring (0-3)) of grey scale synovitis (GS) and power Doppler (PD) (PIP 2-3, MCP 1-5, wrist, elbow, knee, talocrural, MTP 1-5 and extensor carpi ulnaris (ECU)/tibialis posterior (TP) tendons bilaterally) were performed by one rheumatologist (HBH) with high intra-reader reliability (Siemens Acuson Antares, excellence version, 5-13 MHz probe). In addition, both feet were at each examination assessed by dorsal longitudinal scan of all spaces between the MTP joints for IMB. Baseline GS and PD ultrasound and PRJP sum scores of MTP 1-5 bilaterally were calculated. Associations were explored by use of Mann-Whitney test and Odds Ratios (OR).

Results: A total of 43 patients (20.6%) had uni- or bilaterally IMB (27.8% right side, 41.9% left side and 23.3% bilaterally, while 7.0%.had no description of side). The patients had up to 4 IMB (n=1 in 72.1%, n=2 in 14.0%, n=3 in 7.0% or n=4 in 7.0%. The figure shows a typical GS and PD ultrasound of an IMB. The locations of IMB (n=64) were: 4.7% between MTP1 and 2, 32.8% between MTP 2 and 3, 57.8% between MTP 3 and 4, 4.7% between MTP 4 and 5. The presence of IMB was not associated with sum score of baseline GS, PD or PRJP, and not with any of the clinical assessments. However, patients with versus without IMB had significantly higher MTP scores of GS and PD (p=0.05 and p=0.002, respectively), but no difference in PRJP. In addition, presence of IMB was associated with anti-CCP (OR (95% CI) 4.1 (1.2-14.0) and RF (3.7 (1.4-10.1), where 93% of patients with IMB were anti-CCP positive and 87% RF positive.

Conclusion: Intermetatarsal bursitis is quite common in established RA patients and was primarily found between MTP 2-3 and 3-4. It was associated with higher levels of ultrasound MTP joint inflammation and presence of anti-CCP and RF. Thus, ultrasound examination of forefeet should include exploring for this pathology which may indicate more severe disease.

UL av IMB for abstrakt

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/intermetatarsal-bursitis-is-prevalent-in-patients-with-established-rheumatoid-arthritis-and-is-associated-with-anti-ccp-and-rf/