When is Vertebral Body Tethering in a Patient With an Open Triradiate Cartilage a Good Idea?

Background: Vertebral body tethering (VBT) is a fusionless surgical technique used to treat adolescent idiopathic scoliosis (AIS). It is unclear what the optimal window is for surgical intervention using VBT. The purpose of this study is to report the rate of success following VBT in patients with open triradiate cartilage (OTC) and to report the rate of reoperation. Methods: A retrospective review was performed for patients with early-onset scoliosis (EOS) or AIS with OTC who underwent VBT from 2012 to 2020 with a minimum 2-year follow-up. Success was defined as curves <35 degrees at the last follow-up. Failure was subdivided into undercorrection (curves ≥35 degrees at follow-up or reoperation for tether replacement or conversion to fusion) or overcorrection (curves ≥35 degrees in the contralateral direction or reoperation for tether release, or conversion to fusion). The major coronal curve was measured at preoperative, first erect, and annual visits thereafter. Binary logistic regression models were created to correlate demographic and radiographic variables with failed curve correction. Results: A total of 115 patients with OTC (60 EOS, 55 AIS) underwent thoracic VBT. Of these, 87% were female, and 91% of the female patients were premenarchal. The median preoperative Sanders score for all groups was 3. Surgery was successful in 64 patients (56%). Fifty-one patients were classified as treatment failures, 34 (29%) were the result of undercorrection, and 17 (15%) were the result of overcorrection. There was a significant difference in the initial thoracic major curve between success and undercorrection groups (53±10 degrees vs. 60± 8 degrees, P <0.05). There was also a significant difference in the first erect thoracic major curve between success and undercorrection (28±11 degrees and 36±9 degrees, P <0.01). There was a significant difference in the first erect percent correction between success and overcorrection (48±17% and 40±13%, P <0.04). Conclusion: VBT with OTC was successful in 56% of the cases. Undercorrection was associated with a thoracic bend of >51 degrees, percent thoracic correction <54%, and upright preoperative thoracic major curve >79 degrees. Overcorrection was associated with an upright preoperative thoracic major curve <46 degrees. Level of Evidence: Level IV.