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

Abstract

Study design: Retrospective review of a prospectively collected single-center adolescent idiopathic scoliosis (AIS) database.

Objective: To evaluate the incidence and predictors of growth modulation and overcorrection after vertebral body tethering (VBT) in AIS.

Background: 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).

Materials and methods: 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.

Results: 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).

Conclusion: 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.