Complete spinal fusion in patients with ankylosing spondylitis (AS) is most highly associated with greater age at disease onset, nonwhite ethnicity, male gender, and objective markers of disease activity, according to a new study presented at the 2019 American College of Rheumatology (ACR)/Association of Rheumatology Professionals (ARP) Annual Meeting.

To reach this conclusion, the researchers evaluated data of 1253 patients with AS who were enrolled in a longitudinal study of outcome.

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All radiographs were scored for the modified Stoke Ankylosing Spondylitis Scoring System (mSASSS) by the same musculoskeletal radiologist. Complete spinal fusion was defined as a mSASSS score of 72, and no syndesmophyte formation was a mSASSS score of 0. Both were adjusted for disease duration.

A total of 371 patients had either complete spinal fusion at the most recent radiographic assessment (n=63) or no spinal fusion (n=308) and were included in the statistical analysis.

The researchers recorded the following for each patient: sociodemographic features; medication utilization; comorbidities; disease activity based on the Bath Ankylosing Spondylitis Disease Activity Index (BASDAI) and the Ankylosing Spondylitis Disease Activity Score (ASDAS); functional impairment based on the Bath Ankylosing Spondylitis Functional Index (BASFI); joint counts, metrology; and enthesitis assessment.

HLA-B typing, C-reactive protein (CRP), and erythrocyte sedimentation rate were also obtained. Pelvic, lumbar, and cervical spine radiographs were gathered at the baseline visit and every 2 years thereafter.

The median follow-up was 1.92 years (interquartile range, 0-4), with a maximum of 13 years.

Univariable logistic regression models evaluated the factors that were associated with complete spinal fusion compared with those with no radiographic stigmata of AS in the lumbar and cervical spine after adjusting for study site and disease duration.

The analysis identified associations between complete spinal fusion and male gender; nonwhite ethnicity; older age at assessment and at disease onset; a history of smoking; greater functional impairment; unemployment; a negative family history of AS; and elevated baseline CRP.

“These data suggest that complete spinal fusion in patients with AS is most highly associated with greater age at disease onset, non-white ethnicity, male gender, as well as with objective (but not subjective) markers of disease activity,” the researchers concluded.

—Melinda Stevens

Reference:

Maldonado Y, Weisman M, Gensler L, et al. Factors associated with complete spinal fusion in patients with ankylosing spondylitis [abstract 618]. Arthritis Rheumatol. 2019;71(suppl 10). Presented at: 2019 ACR/ARP Annual Meeting; November 8-13, 2019; Atlanta, GA. https://acrabstracts.org/abstract/factors-associated-with-complete-spinal-fusion-in-patients-with-ankylosing-spondylitis/. Accessed November 7, 2019.