Imaging of bone erosion in rheumatoid arthritis.

Rheumatoid arthritis (RA) is the most common type of inflammatory arthritis, with a prevalence of 1% in the United States. Recently introduced disease-modifying antirheumatic drugs have been extremely successful in preventing irreversible joint damage, particularly if initiated early. Accordingly, accurate and early diagnosis of RA has become imperative. This shift places increased demands on imaging to identify even the slightest traces of erosive joint damage and predict future structural and functional deterioration. Unfortunately, conventional radiography has been shown to be insensitive for bone erosions, particularly in early stages of the disease. Computed tomography (CT) is rarely used, but its tomographic perspective offers advantages over projectional radiography. Ultrasound (US) detects more erosions than radiography does and also can evaluate synovitis. Scintigraphy also can detect inflammation and bone turnover at sites of active erosion. It lacks spatial resolution but offers greater anatomical coverage, making whole-body assessments possible. Of all imaging modalities, however, magnetic resonance imaging (MRI) shows the greatest sensitivity for detecting and monitoring bone erosions and also can detect and follow pre-erosive features of RA, such as synovitis, bone marrow edema or osteitis, and tendinous and ligamentous abnormalities. In this article, we review the appearance of bone erosions on conventional radiography and alternative imaging modalities including MRI, CT, US, and scintigraphy. We also review alternative acquisition techniques for MRI in RA and discuss the utility of fat suppression and contrast enhancement.