Degenerative changes of lumbar spine and their clinical implications in patients with axial spondyloarthritis

The objective of this study was to assess degenerative changes (DCs) on magnetic resonance imaging (MRI) of lumbar spine in axial spondyloarthritis (axSpA) and non-specific mechanical low back pain (mLBP). Patients were consecutively recruited and all underwent MRI of the lumbar spine in this cross-sectional study. Disk degeneration (DD, Pfirrmann classification), endplate changes (Modic, types 1, 2, and 3), annular fissure, disk bulging, and protrusion or extrusion at each lumbar spinal level were assessed using anonymized images. Patients with axSpA were assessed for disease activity, functioning, and quality of life. Univariate and subsequent multivariate logistic regression analyses with adjustments of various covariates were used to assess association between MRI findings and clinical variables. One hundred twenty-three patients had non-radiographic (nr-axSpA) and 144 had radiographic axSpA/ankylosing spondylitis (AS). Degenerative changes were more prevalent in patients with mLBP (n = 105) than axSpA. Disk degeneration was the most prevalent MRI finding, followed by annular fissure, disk herniation (protrusion or extrusion), and Modic changes (MCs) in axSpA. Disk herniation was more prevalent in patients with nr-axSpA compared to AS. Modic changes (OR = 6.455), lumbar disk herniation (OR = 2.278), annular fissure (OR = 2.842), conventional synthetic or biologic disease-modifying antirheumatic drugs (csDMARDs) non-users (OR = 2.225), and advanced age (OR = 31.556) were factors associated with an increased risk of DD in axSpA. Coexisting DD increased the burden of disease in axSpA. A considerable proportion of patients with axSpA had DD at the lumbar spine. These degenerative changes might explain some of the complaints and should not been overlooked in patients with axSpA. Key Points • Lumbar herniated nucleus pulposus (LHNP) is more frequent in nr-axSpA while MC is more frequent in AS. • DD may cause an increase in BASFI and BASMI scores in axSpA. • Spinal DCs might be an alternative explanation for low back complaints and should not been overlooked in patients with axSpA.