Relationship between ultrasound damage score of peripheral entheses and spinal bone formation in long-standing radiographic axial spondyloarthritis

OBJECTIVE: To assess structural changes at peripheral entheses and the association with spinal bone formation in patients with long-standing radiographic axial spondyloarthritis (r-axSpA) overall and stratified by sex. METHODS: Peripheral entheses were examined cross-sectionally using ultrasound (US) in patients fulfilling the modified New York criteria for ankylosing spondylitis (AS) and assessed for Outcome Measures in Rheumatology consensus-based structural lesions (enthesophytes, calcifications and erosions) summed to a damage US score (0-42). Spinal radiographs were graded with the modified Stoke AS Spinal Score (mSASSS). Associations between US damage score and mSASSS were assessed with negative binomial regression analyses overall, by sex and by age quartiles. RESULTS: US was performed in 173 patients, 54% males, with a mean (SD) age of 55 (13) years and symptom duration of 29 (13) years. The prevalence of any structural US lesion was 92%. The US damage score was higher in males than females (mean (SD) 4.7 (3.0) versus 3.3 (2.4), p