Lumbar spinal stenosis in axial spondyloarthritis and chronic low back pain: a cross-sectional magnetic resonance imaging study with clinical dimensions.

BACKGROUND: Axial spondyloarthritis (axSpA) may be associated with degenerative spinal lesions that may contribute to lumbar spinal stenosis (LSS), and the overlap of degenerative and inflammatory imaging findings in axSpA complicates diagnosis and treatment. To quantitatively and qualitatively compare lumbar central and lateral stenosis findings on magnetic resonance imaging (MRI) in patients with axSpA to age- and gender-matched controls suffering from chronic low back pain (cLBP), as well as to evaluate associated clinical parameters. METHODS: This cross-sectional cohort study included patients with axSpA and non-SpA mechanical low back pain. MRI were graded for LSS and measured for components of central, foraminal, and lateral recess stenosis including spinal canal, dural sac, neural foraminal area and diameter, spinal canal interfacet width, interpedicular distance, pedicle width, lateral recess height, and ligamentum flavum thickness. Correlations with the clinical and MR dimensions were assessed. RESULTS: Patients with axSpA exhibited lower frequency of LSS, significantly thicker right and left pedicles at upper lumbar levels, higher heights of lateral recesses on both sides of lower lumbar levels, and relatively higher ligamentum flavum thickness at almost all lumbar levels compared to cLBP. CONCLUSION: Compared with cLBP, axSpA was associated with lower frequencies of lumbar spinal stenosis and distinct lumbar spinal morphometric features on MRI. These findings may reflect differing patterns of chronic spinal remodeling between inflammatory and degenerative back pain conditions. Key Points • AxSpA is associated with a distinct lumbar stenosis phenotype compared with cLBP. • Patients with axSpA exhibit lower rates of central, lateral, and foraminal stenosis compared patients with cLBP. • Quantitative MRI reveals thicker pedicles and greater lateral recess heights in axSpA, indicating distinct inflammatory-driven spinal remodeling.