Bilateral vertebral body tethering: identifying key factors associated with successful outcomes

Purpose: The treatment of operative double major pediatric spinal deformities (e.g., Lenke 3 or 6) with bilateral vertebral body tethering (VBT) can be significantly more challenging when compared to other deformity patterns (e.g., Lenke 1) or treatment with a posterior spinal fusion. We aimed to identify preoperative and perioperative characteristics that were associated with successful postoperative outcomes in patients treated with both a thoracic and thoracolumbar (e.g., bilateral) tether. Methods: We retrospectively assessed radiographic and clinical data from patients enrolled in a large multi-center study who had a minimum postoperative follow-up of two years. Standard radiographic parameters were extracted from standing spine and left hand-wrist radiographs at various timepoints. We classified patients based on their preoperative deformity pattern (Primary Thoracic [T_P] vs. Primary Thoracolumbar [TL_P]) and assessed: (1) deformity balance, (2) tilt of the transitional vertebra, and (3) postoperative success. Results: We analyzed data from thirty-six patients (T_P: 19 and TL_P: 17). We observed no relationship between deformity balance at first erect and postoperative success (p = 0.354). Patients with a horizontal transitional vertebra at first erect were significantly (p = 0.001) more likely to exhibit a successful outcome when compared to those who exhibited a tilted transitional vertebra (83% vs. 62%). Patients who had TL_P were also more likely to exhibit a successful outcome when compared to patients who exhibited T_P (76% vs. 50%). Conclusion: These data indicate that double major deformities can be successfully treated with VBT, particularly for those who exhibit TL_P.