Partial bone erosion repair is independently associated with functional improvement in early rheumatoid arthritis: a...

To determine whether change in bone erosion volume detected by high-resolution peripheral quantitative CT (HR-pQCT) is independently associated with functional outcome in early rheumatoid arthritis (ERA).

In this prospective study, 101 patients with ERA received 2-year tight-control treatment aiming at Simplified Disease Activity Index (SDAI) remission (SDAI ≤3.3). HR-pQCT of the second to fourth metacarpophalangeal joints was performed at baseline and at month 24 to quantify erosion parameters. Partial erosion repair was defined as a reduction of at least one erosion count or a decrease in total erosion volume exceeding the least significant change; progression was defined conversely. Functional status was assessed using the Health Assessment Questionnaire-Disability Index (HAQ-DI).

After 2 years, disease activity and HAQ-DI improved significantly (all p<0.001) in paired analyses (n=98). Sixteen (16.3%) patients showed partial erosion repair and 38 (38.8%) erosion progression. In the partial erosion repair group, reduction in total erosion volume correlated strongly with HAQ-DI improvement (ρ=0.719, p=0.003). This association remained significant in linear regression analyses (β=0.607, p=0.003) independent of the contribution from change in SDAI (β=0.453, p=0.018). By contrast, among erosion progressors, change in HAQ-DI was primarily driven by improvement in SDAI (β=0.755, p<0.001). Baseline swollen joint count was associated with erosion progression in univariate analysis (OR 1.177, 95% CI 1.026 to 1.349, p=0.020) and after adjustment for sex (OR 1.171, 95% CI 1.019 to 1.346, p=0.026).

HR-pQCT-detected partial repair of bone erosion was independently associated with functional improvement beyond inflammation control.