Assessing the Learning Curve of the Vertebral Body Tethering in Idiopathic Scoliosis: A Multicenter Analysis

Anterior vertebral body tethering (AVBT) is a promising fusionless alternative for treating idiopathic scoliosis; however, limited data exist on the learning curve for this procedure. Previous studies are limited by single-center and short-term complication data. This multicenter study assesses the learning curve by evaluating improvements in operative characteristics over time and radiographic measurements up to 2 years postoperatively.

As recorded from a multicenter registry, surgeons with ≥10 index AVBT procedures for patients with idiopathic scoliosis aged 16 years and below were included. Relationships between case number and multiple surgical variables were determined using Pearson correlation and linear regression testing. For identification of an inflection point, consecutive cases were plotted against operative time per level and fitted with a locally weighted scatterplot smoothing curve. Independent samples t test and χ 2 test were used to compare outcomes between cases before and after the inflection point. Outcomes of interest included demographic, surgical, and radiographic information at the baseline, immediate postoperative, and 2-year timepointswhere available.

Eight surgeons and 325 index AVBT patients met the inclusion criteria. Inverse relationships were identified between case number and estimated blood loss, operative time, anesthesia time, and fluoroscopic time per level ( P < 0.005). The inflection point was identified at 15 cases. Operative time, anesthesia time, and fluoroscopy time per level were greater in the first 15 cases compared with those after ( P < 0.05). There were no significant differences in demographic variables, intraoperative complications, or length of stay between the early and late cases. Greater correction in the major coronal curve, minor coronal curve, and coronal balance occurred in the cases performed after the inflection point ( P < 0.05).

AVBT is a safe alternative to posterior spinal fusion and demonstrates a predictable improvement in surgical performance over time. Large improvements can be expected during the first 15 AVBT cases performed with minimal differences in complications.

Level III.