Repeated Spinal Mobility Measures and Their Association With Radiographic Damage in Ankylosing Spondylitis

Area of Science:

• Rheumatology
• Orthopedics
• Biomedical Engineering

Background:

• Ankylosing spondylitis (AS) is a chronic inflammatory disease primarily affecting the spine.
• Spinal structural progression, measured by modified Stoke AS Spinal Score (mSASSS), is a key outcome in AS.
• Assessing the relationship between functional mobility and structural changes is crucial for patient management.

Purpose of the Study:

• To investigate the association between changes in repeated spinal mobility measures and longitudinal spinal structural progression in patients with AS.
• To determine if changes in specific cervical and lumbar mobility tests predict radiographic progression.

Main Methods:

• Longitudinal analysis of patients from the Prospective Study of Outcomes in AS (PSOAS) cohort (2003-2019).
• Multivariable regression models assessed relationships between changes in mSASSS and spinal mobility measures (e.g., Schöber's test, occiput-to-wall distance).
• Adjustments were made for clinical/demographic variables and C-reactive protein (CRP).

Main Results:

• No significant associations were found between 2-year changes in individual spinal mobility measures and respective regional mSASSS.
• Baseline mSASSS, male sex, elevated CRP, and longer disease duration were consistently associated with increased longitudinal mSASSS.
• Follow-up duration averaged over 4 years for over 500 patients.

Conclusions:

• Changes in spinal mobility measures over 2 years do not reliably predict AS-related spinal structural progression.
• Baseline mSASSS, sex, CRP levels, and disease duration are significant predictors of spinal structural progression in AS.
• Current mobility assessments may not be sensitive enough to reflect early structural changes in AS.