Pelvic parameters as prognostic factors of radiographic progression in classical Ankylosing Spondylitis: A prospective follow-up data.

Radiographic progression in Ankylosing spondylitis (AS) is driven by mechanical strain. A well-balanced spine provides a favorable weight distribution across the entheses. Pelvic parameters are useful in assessing the shape of the spine. The present study aimed to prospectively investigate the predictive value of pelvic parameters for radiographic progression in AS. This non-interventional, observational, and prospective study enrolled AS patients fulfilling the modified New York criteria (mNY) currently under follow-up in the MARS (MARmara Spondyloarthritis) outpatient clinics. The primary objective was to investigate the relationship between the baseline pelvic parameters and radiographic progression in the spine. Two trained radiologists (EB, OB) independently assessed the modified Stoke Ankylosing Spondylitis Spine Score (mSASSS). An orthopedic surgeon (AHA) and a radiologist (EB) derived the pelvic parameters. Patients with no bridging or bamboo spine were included in the final analysis. Risk assessment for radiographic progression, defined as a two-unit increase in mSASSS or developing a new syndesmophyte every two years, was done using uni- and multivariate logistic regression analyses. Radiographs of 69 AS patients were analyzed. The median (IQR 25-75) prospective follow-up was 47.7 (34.6-52.8) months. Only 33.3% (23/69) had radiographic progression. The pelvic tilt (PT) was lower in patients with radiographic progression (p = 0.037) and each degree of decrease in PT provided a 9% increase in risk for radiographic progression. Male patients were 7.5 times more likely to progress. Pelvic parameters provide a prognostic insight into the radiographic progression in AS. Our observations may aid in selecting patient-specific interventions in addition to anti-inflammatory treatments.