Low-field magnetic resonance imaging study on carpal arthritis in systemic sclerosis--low-grade erosive arthritis of carpal bones is an unexpected and frequent disease manifestation.

Introduction: The aim of the present study was to assess the prevalence and characteristics of subclinical arthritis of carpal and metacarpophalangeal joints in patients with systemic sclerosis (SSc).

Methods: Low-field (0.2 T) magnetic resonance imaging (MRI) was performed in consecutive patients with SSc attending our center between January 2010 and March 2011. Results were assessed in a standardized manner using the Rheumatoid Arthritis Magnetic Resonance Imaging Score (RAMRIS) and standardized assessments of all hand joints. Patients with arthritis due to overlap syndromes were excluded.

Results: Of 38 inpatients and eight outpatients who were screened for inclusion, 30 patients participated in the study and 26 patients could be evaluated. Erosions, bone marrow edema, synovitis, and joint effusions were found in 87%, 37%, 68%, and 58%, respectively, and 24% of patients had additional tenovaginitis. Arthritis affected only a low number of joints per analyzed hand. All bones and joints could be affected, but synovitis and bone marrow edema occurred predominantly in the proximal row of carpal bones, most frequently affecting the lunate bone. The extent of inflammatory changes measured with the RAMRIS correlated significantly with the functional status assessed with the validated German functional score questionnaire Funktionsfragebogen Hannover.

Conclusion: Low-grade arthritic changes on low-field MRI are frequent in patients with pure SSc. The features of arthritis in SSc differ from rheumatoid arthritis. The distribution, the MRI pattern and the predilection for the lunate bone raise the hypothesis that arthritis in SSc may be caused not only by immunological inflammation but also by ischemic mechanisms.