Differentiation of physiological from pathological bone erosions in rheumatoid arthritis: an 8-year HR-pQCT study of the second metacarpal head.

Abstract

To distinguish pathological from nonpathological bone erosions in rheumatoid arthritis (RA) by comparing erosion prevalence and size with healthy controls (HCs) at baseline, as well as long-term evolution and treatment response using high-resolution peripheral quantitative computed tomography (HR-pQCT). We enrolled 247 patients with RA and 78 age- and sex-matched HCs for baseline HR-pQCT of the second metacarpal head. Patients with RA from 2 cohorts-early RA (ERA; n = 98; symptom duration ≤2 years; treated-to-target [T2T] in year 1) and established RA (n = 149; received usual care)-were rescanned after a median of 8 years to quantify erosion volumetric changes. At baseline, small erosions (< 1 mm³) were similarly prevalent in RA and HCs, whereas intermediate (1-5 mm³) and large (> 5 mm³) erosions were more frequent in RA (P < .003). Over 8 years, small erosions in RA were highly stable with minimal volumetric change, whereas large erosions decreased substantially in volume. In patients with large erosions, logistic regression indicated that being in the ERA cohort independently predicted regression of large erosion (odds ratio: 6.93; 95% CI: 1.57-30.56; P = .011). Small erosions are common in both RA and healthy individuals and remain stable long term in RA, supporting their interpretation as physiological/biomechanical (noninflammatory) variants rather than RA pathology. In contrast, large erosions are specific to RA and show significant capacity for repair under early, aggressive T2T management.