Learning Curve Associated With Thoracoscopic Anterior Vertebral Body Tether and Double Anterior Vertebral Body Tether for Idiopathic Scoliosis: Analysis of Three Independent Surgeons.

Background and objectives: Anterior vertebral body tether (VBT) is a fusionless approach to treat idiopathic scoliosis, and surgeons are beginning to implement the technique into current practice. This study aims to evaluate the learning curve for single and double VBT.

Methods: A retrospective review of 3 surgeons' first 40 single and 20 double VBT was performed. Skeletally immature patients with idiopathic scoliosis who underwent thoracic (single) or thoracolumbar (double) VBT were included. Thoracic VBT was done via video-assisted thoracoscopic surgery and lumbar VBT through a mini-open retroperitoneal approach. Primary outcomes of interest were operative time, radiation exposure, and radiographic correction. Pooled and individual-surgeon analyses were performed.

Results: A total of 180 patients were included: 120 single and 60 double. Mean age was 12.7 years, and 87.8% were female. Mean segments tethered was 7.8 in single and 11.0 in double. Mean preoperative thoracic scoliosis was 51.5: single 50.5° and double 53.3°. Mean lumbar scoliosis was 36.4°: single 30.0° and double 49.0°. Average operating time was 276.2 minutes; double VBT was significantly longer (217.3 vs 394.0 minutes, P < .001). Mean blood loss was 198.5 mL, and mean fluoroscopy dose was 73.0 mGy. For single VBT, there was a decrease in operative time (283.3-174.8 minutes, P < .001) and fluoroscopy dose (70.1-53.5 mGy, P = .047) over time. Every 10 cases resulted in a 31.4 minute decrease in operative time ( P < .001). There were no intraoperative complications. Single VBT resulted in 54.9% thoracic curve correction. Double VBT achieved 53.0% thoracic and 56.7% lumbar correction. There were no differences in curve correction across the learning curve.

Conclusion: VBT is viable fusionless surgical option for scoliosis. As expected, increased experience resulted in shorter operative time; the threshold for such improvement seems to be 10 cases. Importantly, adequate and consistent curve correction can be achieved at the start of the learning curve while mitigating complications.