Background Ultrasound (US) with very high frequency probe (up to 22 MHz) has a resolution power of 0.1 mm and allows for the direct visualization of the hyaline cartilage of the metacarpal head.
Objectives To determine the prevalence and distribution of US-detected cartilage damage at metacarpal heads of patients with rheumatoid arthritis (RA) and osteoarthritis (OA) and to investigate if cartilage damage evaluated by US method is associated with radiographic scores (Sharp van der Heijde score and Simple Erosion Narrowing Score (SENS) in RA and Kallman score in OA).
Methods 50 patients with RA and 19 patients with OA were enrolled in this study. The US examination of the metacarpal head cartilage from II to V finger of both hands was performed. 400 metacarpophalangeal (MCP) joints in RA and 152 MCP joints in OA were scanned with a very high-frequency linear probe (i.e. 10–22 MHz), using a previously described scoring system for cartilage damage1. In a subgroup of 27 patients with RA and 7 with OA the radiographic scores were calculated. Pearson's correlation coefficient and Cohen κ were used to investigate associations between US and radiographic scores.
Results The US examination of the metacarpal head cartilage from II to V finger of both hands lasted a mean of 6 minutes. The metacarpal head cartilage was found positive for cartilage damage by US in 139 out of 400 (34.8%) MCP joints in RA and in 65 out of 152 (42.8%) MCP joints in OA. In RA, the hyaline cartilage of the II right metacarpal head was the most frequently affected followed by the II left and the III right metacarpal head. The less affected was the V metacarpal head bilaterally. In OA, cartilage damage was homogeneously distributed in all MCP joints. Symmetric damage of cartilage was observed in 97/400 (24.3%) RA joints and in 44/152 (28.9%) OA joints. Conversely, asymmetric damage of the cartilage was observed in 42/400 (10.5%) RA joints (only in patients with disease duration more than 2 years) and in 21/152 (13.8%) joints in OA. A significant positive correlation was found between US total score and either Sharp van der Heijde score or SENS score (r=0.584, p<0.001; r=0.510, p<0.001, respectively) in RA and between US total score and Kallman score (r=0.687, p<0.001) in OA. Agreement between two imaging methods was high, 78% in RA (κ=0.570, p<0.001) and in 91% in OA (κ=0.750, p<0.001).
Conclusions The present study provides evidence supporting the feasibility of the US assessment of the metacarpal head cartilage. A positive significant correlation was found between the US findings, obtained with a very high frequency probe by an experienced sonographer and the radiographic scores assigned by an expert radiologist.
Filippucci E et al: Interobserver reliability of ultrasonography in the assessment of cartilage damage in rheumatoid arthritis. Ann Rheum Dis 2010, 69(10), p. 1845–1848.
Acknowledgement Supported by EULAR, IGA grant No. NT12437 and GAUK grant No. 1010213.
Disclosure of Interest None declared