Imaging of axial spondyloarthritis. New aspects and differential diagnoses.

Axial spondyloarthritis (axSpA) is a chronic rheumatic disease characterised by inflammatory back pain and several other disease manifestations and comorbidities. The 2009 ASAS classification criteria differentiate between the classical ankylosing spondylitis or radiographic axSpA and non-radiographic axSpA based on the presence or absence of definite radiographic changes in the sacroiliac joints. Importantly, back pain in patients with axSpA may well have reasons other than axial inflammation or new bone formation. There are several important differential diagnoses such as diffuse idiopathic skeletal hyperostosis and osteitis condensans. This review summarises recent publications concerning the performance of imaging modalities in the field, such as conventional radiography, magnetic resonance imaging, computed tomography and dual energy x-ray absorptiometry including the trabecular bone score.