Background Early detection of bone erosions in rheumatoid arthritis (RA) is essential for initiating or intensifying treatment and improving outcome. To date, conventional radiography (CR) is considered the gold standard to detect joint damage. Magnetic resonance imaging (MRI) has shown to be superior over CR with respect to detecting erosions, and also visualizes the inflammation itself, but may not be feasible in daily practice. High-Resolution peripheral Quantitative Computed Tomography (HR-pQCT), a novel imaging technique, allows three dimensional analysis of cortical and trabecular bone structure in finger joints at a micro level. Previous research showed that HR-pQCT is able to detect more erosions than CR.
Objectives First, to cross-sectionally compare the number of erosions detected by HR-pQCT with erosions detected on CR and MRI, in second and third MCP and PIP joints of patients with RA and healthy controls (HC). Secondly, to compare erosions scored by HR-pQCT with erosions, synovitis and bone marrow edema (BME) on MRI images.
Methods In total, 56 joints (30 MCP and 26 PIP) from 9 patients (3 early RA patients diagnosis since <2 years, 3 late RA patients diagnosis since >10 years, and 3 HC) were imaged by HR-pQCT (82 μm, Scanco XtremeCT), CR and MRI (Philips 3T). HR-pQCT images were scored for erosions by one reader according to a modified SPECTRA (Study grouP for xtrEme Computed Tomography in Rheumatoid Arthritis) algorithm. An erosion was defined as a cortical break seen on two consecutive slices in at least two planes (transverse, coronal or sagittal). MRI was independently scored for the presence of erosions, synovitis and BME by two radiologists. CRs were independently scored for the presence of erosions by one rheumatologist. Scoring of images was done on proximal and distal sites of MCP and PIP joints. Descriptive statistics were calculated. For the difference in total number of erosions on HR-pQCT, MRI and CR, Wilcoxon signed rank test was used.
Results The total number of erosions detected was 62, 14 and 8 for HR-pQCT, MRI and CR respectively. Significantly more erosions were scored on HR-pQCT compared to, respectively, MRI and CR (p=.02 and p=.02). Erosions were scored in 7 out of 9 subjects on HR-pQCT, 3 out of 9 subjects on MRI and 2 out of 9 subjects on CR. Most erosions were scored in the late RA group (49 erosions on HR-pQCT, 12 on MRI and 6 on CR). Of the erosions in the late RA group, eleven erosions were detected on both HR-pQCT and MRI on the same joint site, and six of these erosions had concomitant synovitis and BME on MRI. Among the early RA patients, only 1 had synovitis and BME on MRI, but without erosions on HR-pQCT or CR.
Conclusions HR-pQCT detects significantly more erosions than MRI and CR. The relation between scores of synovitis and BME on MRI and early detection of erosions with HR-pQCT needs to be further explored in a larger cohort and in longitudinal studies.
Stach. Arthritis Rheum. 2010; 330-339.
Disclosure of Interest A. Scharmga: None declared, M. Peters: None declared, J. van den Bergh: None declared, D. Loeffen: None declared, B. van Rietbergen Consultant for: Scanco Medical AG, A. van Tubergen: None declared, R. Weijers: None declared, P. Geusens: None declared