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

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.

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.

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).

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.

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.