Impact of Ankylosing Spondylitis/Diffuse Idiopathic Skeletal Hyperostosis on Postoperative and Patient-Reported Outcomes Following Elective Cervical and Lumbar Surgery

Study Design Retrospective cohort. Objective Limited evidence exists for outcomes after elective cervical and lumbar fusion in patients with ankylosing spondylitis (AS) or diffuse idiopathic skeletal hyperostosis (DISH). This study aimed to compare perioperative and patient-reported outcomes between patients with AS/DISH and matched control patients. Methods Adults with AS/DISH undergoing primary elective ACDF, PCDF, PLDF, or TLIF from 2004-2023 were identified. AS/DISH patients were propensity score matched (1:3) to controls without ankylosing disorders. Outcomes included readmission rates, discharge disposition, revision/reoperation, and patient-reported outcome measures at baseline and follow-up. Chi-square and t-tests were used, with P < 0.05 as significant. Results 66 AS/DISH patients (42 cervical, 24 lumbar) were matched to 198 controls. AS/DISH patients had higher Charlson Comorbidity Index scores and greater 0-30 day readmission rates for both cervical (9.5% vs 1.6%, P = 0.035) and lumbar (20.8% vs 2.8%, P = 0.010) fusions. Cervical AS/DISH patients demonstrated superior VAS Neck, VAS Arm, and mJOA scores at several postoperative timepoints. Lumbar AS/DISH patients showed greater early VAS Back improvement (Δ6-month −4.00 vs −2.91, P = 0.010) but smaller VAS Leg gains (Δ6-month −1.50 vs −4.13, P = 0.021). Multivariable regression controlling for CCI score, male sex, and AS/DISH diagnosis identified that a diagnosis of AS/DISH was independently associated with greater odds of 30-day readmissions (OR: 6.04, 95% CI: 1.84-23.38, P = 0.004). Conclusion AS/DISH is associated with increased short-term readmissions after elective spinal fusion, despite some superior functional outcomes in cervical procedures. Future studies should evaluate whether targeted perioperative optimization can reduce these risks.