Background/Purpose:   Low field extremity MRI has been utilized to evaluate patients for inflammatory arthritis and to follow their progress on immunosuppressive and biologic therapy.  The interpretation is performed by radiologists experienced in evaluating extremity MRI scans, but how often do the findings agree with the clinical evaluation?  The purpose was to evaluate hand and wrist pain to determine whether patients have changes of inflammatory arthritis and are good candidates for immunosuppressive or biologic therapy. 

Methods:   We analyzed our rheumatology office practice patients who had extremity MRI of the hand and wrist performed in 2010 through 2012. All patients received low field MRI evaluations of the wrist and hand, using an Esoate .2 Tesla C Scanner.  We compared the patient’s clinical diagnosis to the MRI findings. The MRI radiologists assessed whether synovitis was present and its intensity and location, the presence of osteitis; bone erosions and joint space narrowing.

Results:  Mild synovitis was frequently reported in patients with fibromyalgia.  Erosions were occasionally seen in fibromyalgia patients, but they were almost always solitary or a few small erosions whereas, as expected, in rheumatoid arthritis the synovitis was more intense and the erosions were more frequent and more extensive.  Osteitis was reported in RA and OA patients and helped distinguish their MRI scans from those with fibromyalgia.  

Conclusion:   We conclude that MRI scans of the extremities are helpful in evaluating patients with hand pain, but caution is necessary to avoid over-interpretation of mild findings, especially mild synovitis and small and rare erosions.  Patients with inflammatory arthritis had moderate to severe synovitis that was present in more locations (the MCP joints, PIP joints, and the carpal joints) than patients with the clinical diagnosis of non-inflammatory arthritis, or fibromyalgia. However, a few patients thought originally to have fibromyalgia were considered for treatment of inflammatory arthritis based on the MRI findings.  Mild synovitis without gadolinium is difficult to evaluate accurately. 72.3% of patients with RA were not interpreted as consistent with this diagnosis indicating either effective treatment or under interpretation of MRI findings.

The MRI scans of patients with fibromyalgia and non-inflammatory arthritis are frequently reported as abnormal. Mild changes on extremity MRI can be seen in patients with fibromyalgia and should not lead to a change of diagnosis. The same applies to those with non-inflammatory arthritis. Generally, a distinction can be made compared to those with inflammatory arthritis based on the intensity and widespread distribution of the synovitis, the number and size of erosions, and the presence of osteitis. 

Over-interpretation and under interpretation of extremity MRI by experienced radiologists is common.