Differences in spinal structural lesions between patients with early axSpA and non-axSpA chronic back pain: 2-year...

To compare spinal structural lesions on radiography and magnetic resonance imaging (MRI) over 2 years, between patients with early axial spondyloarthritis (axSpA) and non-axSpA chronic back pain.

Patients from the SPACE cohort with available radiography or MRI at both baseline and 2years were included. Spinal lesions on radiography were assessed by the modified Stoke Ankylosing Spondylitis Spine Score (mSASSS), corner MRI lesions by the modified Canada-Denmark scoring system. Baseline spinal structural lesions and 2-year changes were compared between axSpA and non-axSpA. Generalized estimating equations were used to assess the change over 2 years, adjusting for age, sex, non-steroidal anti-inflammatory drug use and diagnosis.

Radiography data from 318 patients (67% axSpA), MRI data from 351 patients (69% axSpA) were included. At baseline, the mean (SD) mSASSS was 0.6 (1.1) for both axSpA and non-axSpA. Over 2 years, mSASSS progression was minimal (0.01 units/year) in both groups. On MRI, axSpA patients had a mean of 1.4 (2.9) total structural lesions compared with 0.7 (2) in non-axSpA at baseline (P = 0.12). Significant 2-year increase in structural lesions [0.5 (1.8)] was mainly due to fat lesions [0.5 (1.6)] in axSpA. On MRI, fat lesions changed at a rate of 0.16 units/year in axSpA (P = 0.002) and -0.02 units/year in non-axSpA (P = 0.70).

Over 2 years, spinal structural damage typical for axSpA progressed minimally on radiography in axSpA and non-axSpA. On MRI, axSpA showed a significant increase in fat lesions, while non-axSpA had no progression. Fat lesions may be important to assess spinal changes from early disease onwards.