Imaging in spondyloarthropathies

Seronegative spondyloarthropathies comprise a group of inflammatory arthritides, which consists of ankylosing spondylitis, psoriatic arthritis, reactive arthritis (Reiter's syndrome), enteropathic arthritis, and undifferentiated spondyloarthropathy. All of them share common laboratory, clinical, and imaging findings, with characteristic involvement of the sacroiliac joints, spine, and, to various degrees, peripheral joints. For many years, conventional radiography was the mainstay for definitive diagnosis of sacroiliitis and for follow-up of the anatomic changes in the spine, peripheral joints, and entheses. Conventional radiographs remain the imaging investigation of choice; however, they are unable to detect early inflammatory changes of sacroiliitis, which are important for establishing a diagnosis without delay. Other imaging modalities, such as computed tomography, bone scintigraphy, magnetic resonance imaging, and ultrasonography have improved the capabilities of detecting early disease and became useful adjuncts to plain films. In addition, they also have enabled more accurate detection of pathology at various anatomic sites of the musculoskeletal system predominantly involved in spondyloarthropathies. This article will review and highlight the role of each of these modalities in the assessment of the axial and peripheral skeleton in seronegative spondyloarthropathies.