Are patients who return for 10-year follow-up after AIS surgery different from those who do not?

Purpose To evaluate the impact of patients lost to follow-up on outcomes of surgery for adolescent idiopathic scoliosis (AIS) at 10-year postoperative. Methods Preoperative, 2-year, and 5-year postoperative demographic, radiographic, and SRS-22 data from a prospective multi-center registry were compared between patients with a 10-year follow-up visit versus those without. A second analysis utilized variables that were different between the groups, along with SRS scores, in a cohort of patients with preoperative, 2-, 5-, and 10-year postoperative SRS scores (complete cohort) to impute missing 10-year data (imputed cohort) utilizing Markov chain Monte Carlo simulation. Results 250 patients had 10-year follow-up (21%). Those with 10-year follow-up had a greater percentage of patients who underwent anterior procedures (p < 0.05). Radiographically, the groups were similar at all three time points. SRS-22 scores demonstrated slightly worse pain and function preoperatively and at 2 year in those lost to follow-up (effect size eta = 0.11-0.12), with no differences at 5 year. Imputed data analysis demonstrated similar trends over time in SRS-22 scores compared to the complete cohort for total score and all domains except pain. There was no significant difference in imputed versus complete 10-year SRS-22 scores (p > 0.05). Conclusion This study identified early differences between patients with 10-year follow-up and those without, though effect sizes were small and non-existent at 5 years. SRS-22 scores at 10 year between the complete and imputed data sets did not differ. Clinically relevant outcomes of the subset who followed-up at 10 year are likely generalizable to the entire eligible AIS population.