Clinical outcomes and progression to orthopedic surgery in juvenile- versus adult-onset ankylosing spondylitis

Objective Juvenile- and adult-onset ankylosing spondylitis (AS) are subtypes of AS that may have different clinical outcomes. We compared cohorts of juvenile-onset AS and adult-onset AS in terms of clinical characteristics, clinical outcomes, proceeding to AS-related orthopedic surgery, and type of orthopedic surgery. Methods A retrospective cohort study was conducted of all AS patients attending a teaching hospital. Demographics, clinical parameters, and history of AS-related orthopedic surgery to the spine, root, or peripheral joints were recorded. Differences between surgery for juvenile- and adult-onset AS patients, and effects of covariates were assessed using logistic regression and survival analyses. Results A total of 553 AS patients were studied: 162 juvenile-onset AS and 391 adult-onset AS cases. After adjusting for significant covariates, adult-onset AS cases were less likely to proceed to surgery (odds ratio [OR] 0.31, P < 0.001), have a hip procedure (resurfacing or arthroplasty; OR 0.374, P = 0.001), and have hip arthroplasty (OR 0.43, P = 0.01). Significant differences were also observed when comparing Kaplan-Meier survival curves (P = 0.001) and using Cox proportional hazards regression (P = 0.002). A history of smoking was not associated with surgery. AS cases with older age at symptom onset were far less likely to have surgery than those with younger onset, in a nonlinear manner. Conclusion Juvenile-onset AS cases are more likely than adult-onset AS cases to proceed to hip arthroplasty, but equally likely to have hip resurfacing and hip arthroplasty revision/re-revisions. Smoking was not associated with the risk of orthopedic surgery. Orthopedic surgery was unlikely after 40 years of disease in both subsets.