Who are the best candidates? Factors predicting success and failure of vertebral body tethering.

PURPOSE: Vertebral body tethering (VBT) is a fusionless alternative for adolescent idiopathic scoliosis (AIS), but predictors of long-term success remain unclear. We aimed to report outcomes 2-8 years following VBT and identify factors associated with revision surgery. METHODS: Single institution retrospective review of a prospectively collected AIS database. INCLUSION CRITERIA: VBT between 2015-2022, skeletal maturity (Risser 5 or Risser 4 with Sanders 7) at follow-up, and minimum 2-year follow-up or revision surgery. Patients were classified as not requiring revision surgery (NRS) or requiring revision surgery (RS). RESULTS: Forty-one patients were included: 21 (51%) NRS and 20 (49%) RS. Mean follow-up was 4.3 years (NRS) and 3.6 years (RS). Compared with RS, NRS patients had lower preoperative curve magnitude (46° vs. 52°, p = 0.03) and higher Sanders stage (3.4 vs. 2.4, p = 0.01). Sanders <3 (OR = 9.2, 95% CI 1.3-67.3, p = 0.03) and preoperative curve magnitude (OR = 2.7 per 10°, 95% CI 1.1-6.8, p = 0.04) were independent predictors of revision surgery. Double curves had higher revision rates (86% vs. 41%); 30% of RS patients had double curves versus 5% of NRS. Immediate correction to <35° was achieved in 67% (NRS) vs. 25% (RS) (p = 0.01). Final Cobb angle was 25° (NRS) vs. 34° (RS) (p = 0.003). CONCLUSIONS: VBT patients not requiring revision surgery had preoperative curves <50° and more advanced skeletal maturity (Sanders 3.4 vs. 2.4). These patients were more likely to achieve immediate correction to <35° and maintain correction at follow-up. These factors should be considered when selecting patients for fusionless techniques and inform preoperative counseling regarding revision risk.