Background/Purpose: Imaging studies have shown that erosions emerge early in RA and is associated with worsening pain and function. Despite erosions being just as prevalent in feet as in hands in patients with RA, their development in relation to synovitis and bone marrow edema (BME) have mainly been studied in the hands. This study examines the prevalence and longitudinal trajectory of erosions, BME, and synovitis in metatarsophalangeal joints (MTPJs) in patients with early RA over 2 years of treatment. We also describe correlations between changes in erosions, synovitis, and BME at the joint level.

Methods: Treatment naïve patients with early RA (symptom duration < 2 years) were recruited from an academic rheumatology clinic. MRI of the most symptomatic forefoot was acquired at baseline, year 1 and ≥2 years using a 1.0T peripheral scanner (GE Medical). Metatarsophalangeal joints 2-5 were semi-quantitatively graded by a MSK radiologist for erosions (0-10), synovitis (0-3) and BME (0-3) according to OMERACT guidelines. Synovitis was graded per joint, while erosions and BME were graded for the metatarsal head and phalangeal base individually so the maximum scores per MTPJ were 20 for erosions and 6 for BME. The MSK radiologist was blinded to clinical assessments and previous imaging. Patients were treated per standard of care. Descriptive statistics characterized the study population. Paired t-tests were performed for changes in erosions, synovitis, and BME over time. Correlations between changes in erosions, synovitis, and BME were conducted per joint using Pearson’s correlation coefficient.

Results: 32 patients with early RA were included. 87.5% of patients were female and the average age was 51.7 (SD=10.4). At baseline, 29 patients (90.6%) had at least one grade ≥1 erosion, 21 (65.6%) had at least one MTPJ with grade ≥1 synovitis, and 19 (61.3%) had at least one joint with grade ≥1 BME. The proportion of MTPJs with erosions, synovitis, and BME are shown in Table 1. Overall changes in erosions, synovitis, and BME are shown in Figure 1. Erosions overall did not significantly change over time. Significant reductions in overall synovitis scores, MTPJ2, and MTPJ3 synovitis scores were seen between year 1 and ≥2 years.  Overall BME scores improved in year 1 and were sustained at ≥2 years. BME improved in MTPJ2, MTPJ3, and MTPJ4. Positive correlations were seen between changes in synovitis and BME in MTPJ2 and MTPJ5.

Conclusion: In patients with early RA, standard of care saw overall reductions in synovitis by year 2, BME by year 1, and no progression in overall erosion scores on MRI. MTPJ2 and MTPJ3 appeared to be the most active joints.  Overall improvements in synovitis is attributed to MTPJ2 and MTPJ3, while other MTPJs did not progress. Over all reductions in BME is attributed to MTPJ2, MTPJ3, and MTPJ4, while other MTPJs did not progress. 

Table 1. Proportion of joints with erosions, synovitis, and BME over time

Figure 1. Longitudinal changes in overall erosions, synovitis, and BME

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/prevalence-and-trajectory-of-erosions-synovitis-and-bone-marrow-edema-in-feet-of-patients-with-early-rheumatoid-arthritis/