High-frequency ultrasound semi-quantitative assessment of cartilage damage in rheumatoid arthritis using the outcome measures in rheumatology scoring system.

Background: Rheumatoid arthritis (RA) is a chronic inflammatory disease characterized by progressive joint destruction, including cartilage damage. High-frequency ultrasound (US) enables direct visualization of cartilage in small hand joints. This study aimed to characterize the distribution and burden of US-detected cartilage damage in patients with RA using the Outcome Measures in Rheumatology (OMERACT) scoring system and to compare these findings with those from patients with hand osteoarthritis (OA) and healthy controls (HCs). Methods: In this single-center cross-sectional study, 129 patients with RA, 36 patients with hand OA, and 59 HCs were enrolled. The second and third metacarpophalangeal (MCP) and proximal interphalangeal (PIP) joints of both hands were examined using a 24-MHz linear probe. Cartilage damage was semi-quantitatively scored using the OMERACT 0-2 grading system, and cartilage thickness was measured quantitatively. Patient-level count outcomes were analyzed using negative binomial regression, maximum cartilage grade using ordinal logistic regression, and joint-level cartilage damage using logistic generalized estimating equations to account for clustering within patients. Spearman correlation was used to assess associations between cartilage scores and clinical and sonographic parameters. Results: A total of 1,792 joints were analyzed. Cartilage damage (grade ≥1) was observed in 46.5% of RA patients, 38.9% of OA patients, and 11.9% of HCs. Severe cartilage damage (grade 2) was observed in 10.1% of RA patients and 11.1% of OA patients, but in none of the HCs. Compared with OA, RA patients showed significantly higher MCP total cartilage scores [incidence rate ratio (IRR) =2.17; 95% confidence interval (CI): 1.12-4.20; P=0.021], a greater number of affected joints (IRR =1.92; 95% CI: 1.08-3.43; P=0.027), and higher overall cartilage grade scores (IRR =1.76; 95% CI: 1.01-3.06; P=0.046). At the joint level, RA was associated with higher odds of cartilage damage than OA after adjustment and clustering correction [odds ratio (OR) =1.91; 95% CI: 1.03-3.57; P=0.041], mainly driven by MCP involvement (OR =2.85; 95% CI: 1.27-6.39; P=0.011). Cartilage damage in RA predominantly involved the right MCP2 and MCP3 joints, whereas OA showed a more uniform distribution with relatively greater PIP3 involvement. MCP and PIP thickness did not differ between RA and OA (P=0.327 and P=0.861, respectively), but both were significantly lower in RA than in HCs (both P<0.001). Established RA showed a higher prevalence of cartilage damage than early RA (62.5% Conclusions: High-frequency US using the OMERACT system demonstrated that RA is characterized by a higher overall cartilage damage burden and a distinct MCP-predominant distribution pattern, rather than greater maximum single-joint severity. US semi-quantitative cartilage grading may support structural characterization of RA in comparison with hand OA and HCs, but longitudinal studies are needed to determine its prognostic and monitoring value.