Incidence and Predictors of Growth Modulation and Overcorrection after Anterior Vertebral Body Tethering.

Abstract

Retrospective review of a prospectively collected single-center adolescent idiopathic scoliosis (AIS) database. To evaluate the incidence and predictors of growth modulation and overcorrection after vertebral body tethering (VBT) in AIS. Little data exists regarding which AIS patients will exhibit growth modulation and/or overcorrection after VBT compared to those whose curve correction will remain unchanged (no modulation). A total of 279 patients with AIS with a minimum 2-year follow-up (range 2-10 years) were included. There were 262 thoracic and 65 thoracolumbar VBT surgeries performed. Univariate and multivariate regression analyses were performed to identify the potential clinical/radiographic predictive factors for growth modulation and overcorrection. Patients with growth modulation and those with no modulation after thoracic VBT were significantly more immature (younger, premenarchal, lower Sanders score/Risser grade, open triradiate cartilage [TRC]) and physically smaller (lower height, weight, and body mass index [BMI]; P<0.02). Patients with growth modulation vs. no modulation after thoracolumbar VBT had lower preoperative Sanders score, weight, and BMI (P<0.04). Preoperative and first-erect thoracic and lumbar curve magnitudes did not affect growth modulation vs. no modulation. Patients with thoracic overcorrection were physically smaller (lower height/weight/BMI) and had lower preoperative and first-erect thoracic curves than patients with growth modulation without overcorrection (P<0.04). Patients with thoracolumbar overcorrection had open-TRC and lower first-erect lumbar curves than patients with growth modulation without overcorrection (P<0.04). Open-TRC (odds ratio: 6.8, P<0.001) and lower BMI (P<0.001) were the only significant predictive factors for thoracic growth modulation in multivariate analysis; none were identified for thoracolumbar growth modulation. Sixty-four percent of patients with overcorrection required revision surgery versus 18% of those with no modulation (P<0.001). AIS patients with open-TRC and lower BMI had a statistically higher rate of thoracic growth modulation and overcorrection after VBT in multivariate analysis. Preoperative and first-erect curve magnitudes did not affect the incidence of growth modulation.