Objective: To investigate the frequency and distribution of finger tenosynovitis in patients with early, untreated rheumatoid arthritis (RA) using gray-scale ultrasound (US) and magnetic resonance imaging (MRI).
Methods: Fifty patients underwent US and MRI of metacarpophalangeal (MCP) joints 2-5. Twenty healthy controls underwent US only. Flexor and extensor involvement was documented for each joint. Intrareader reliability (IRR) was calculated by rereading static images.
Results: Flexor tenosynovitis was found in 57 (28.5%) of 200 joints in 24 (48%) of 50 patients on US compared with 128 (64%) of 200 joints in 41 (82%) of 50 patients on MRI. Periextensor tenosynovitis was found in 14 (7%) joints in 9 (18%) patients on US compared with 80 (40%) joints in 36 (72%) patients on MRI. No controls had imaging tenosynovitis. Using MRI as the gold standard, the sensitivity, specificity, and negative and positive predictive values for US were 0.44, 0.99, 0.49, and 0.98, respectively, for flexor tenosynovitis and 0.15, 0.98, 0.63, and 0.86 for extensor tenosynovitis, respectively. The IRR was 0.85 and 0.8 for US and MRI, respectively. The most frequently involved joints on US and MRI were the second and third MCP joints.
Conclusion: This is the first study to compare US and MRI for the detection of tenosynovitis in the fingers of patients with early untreated RA. Tenosynovitis was found to be common using both modalities, with MRI being more sensitive. A negative US scan does not exclude inflammation and an MRI should be considered. Further work is recommended to standardize definitions and image acquisition for both US and MRI images.