The presence of bone erosions on radiographic imaging is one of the diagnostic criteria for rheumatoid arthritis. Modern management of rheumatoid arthritis emphasizes early intervention with disease-modifying agents when disease progression is apparent. Initial studies of magnetic resonance imaging (MRI) have suggested a greater sensitivity for detection of bony erosions than standard radiography. Østergaard and colleagues performed a five-year follow-up study comparing MRI and radiography for detection of new bone erosions in patients with rheumatoid arthritis.

The authors followed 10 patients who fulfilled the American College of Rheumatology criteria for rheumatoid arthritis. MRI and radiography of the dominant wrist were performed annually for five years. All patients were taking disease-modifying agents at study entry. Of the 150 carpal bones initially imaged, nine erosions were detected by radiography at baseline.

A total of 27 new bone erosions were detected by radiography over the five years of the study. MRI was able to detect 21 of the erosions earlier than radiography. Three erosions were detected at the same time, two erosions were found earlier with radiography, and one erosion found by radiography was never apparent with MRI. On average, MRI was able to detect bone erosions two years before they were apparent on radiographs. The presence of bone erosions on MRI was predictive of progression to erosions visible by radiography at the end of the five-year follow-up. In patients with erosions detectable by MRI at baseline, the risk of progression to a radiographically visible erosion by the end of the study was increased 4.5-fold.

The authors conclude that MRI is more sensitive than standard radiography in the detection of bone erosions in patients with rheumatoid arthritis. MRI can identify new erosions at least one year earlier than radiography, and patients with abnormalities on MRI are more likely to have progressive disease.