Two to five years pulmonary functions after thoracic, thoracolumbar and bilateral vertebral body tethering surgery.

Purpose: Adolescent Idiopathic Scoliosis negatively impacts chest wall development. Bracing and fusion surgery have shown varied effects on pulmonary outcomes. Vertebral Body Tethering presents a growth-sparing alternative that might mitigate these effects by reducing biomechanical disruptions. Aim was to evaluate changes in pulmonary functions during the course of the follow-up after VBT surgery.

Methods: Retrospective cohort study including patients who underwent Thoracic, Thoracolumbar and Bilateral VBT surgery with a minimum 24 months follow-up. Forced Vital Capacity (FVC%), Forced Expiratory Volume in the first second (FEV1%) and FEV1/FVC ratio were evaluated at multiple time points. Four groups were formed using main curve location and surgical technique. Analyses of variance were used to assess changes over time.

Results: 81 consecutive patients (76F, 5 M; 12.5 ± 1.6 years) with a mean follow-up 53.4 (24-105) months were included. Preoperatively, the median Sanders was 3 (1-7) and the median Risser was 0 (- 1-5). The mean MT curve of 50.8º ± 11.0º was corrected to 26.0º ± 7.3º at 6 weeks, which was modulated to 22.4º ± 13.4º. FVC%, FEV1%, and FEV1/FVC showed significant improvements over time for the entire cohort up to 2-3 years (p < 0.0005) where the curve type and surgical technique influenced improvement patterns. For patients with longer follow-up, values at 4-6 years did not differ from those at 2-3 years (p > 0.05, for all comparisons).

Conclusions: Thoracoscopic VBT surgery led to consistent increases in FVC%, FEV1%, and FEV1/FVC values across the entire cohort, which were sustained at longer follow-up in a subset of patients. Surgeries on thoracic curves showed more pronounced improvements compared to thoracolumbar curves.

Key points: Pulmonary function test results (FVC%, FEV1% and FEV1/FVC) improved following VBT surgery for AIS patients. Thoracic and thoracolumbar surgery for thoracic curves, and bilateral surgery resulted in more pronounced FVC% and FEV1% improvements. Improvement in FVC% and FEV1% values started earlier after Thoracic VBT. Thoracolumbar surgery for thoracolumbar curves displayed significant improvement only in FEV1/FVC results, as they had better preoperative pulmonary functions. Observed improvements in FVC%, FEV1% and FEV1/FVC were preserved at 4-6 and 7-8 years follow-up in a subset of patients, averaging a mean duration of 48.7 months for the whole cohort.