Correlation between age, coronal and sagittal parameters and spine flexibility in patients with adolescent idiopathic scoliosis

To investigate the correlation between spine flexibility and age, skeletal maturity, coronal and sagittal parameters for adolescent idiopathic scoliosis (AIS). All AIS patients evaluated for surgery were included. Following parameters were obtained: age, gender, skeletal maturity (Risser and Sanders), Cobb angle at high thoracic (HT), mean thoracic (MT) and thoracolumbar/lumbar (TL/L) level, flexibility of HT, MT and TL/L curves, coronal and sagittal parameters. A multivariate diagnostic through the Pearson Product–Moment Correlation Coefficient ( $$r$$ ) was performed. Data from 200 patients were obtained (30 males, age 15 ± 1.9 years). No significant correlation was found between curve flexibility and age or gender. A negative correlation was observed between flexibility of MT curves and magnitude of HT ( $$r$$ = − 0.4) and MT curves ( $$r$$ = − 0.4). A weak correlation among curve flexibility at different levels was observed: the flexibility of HT curves correlated with the flexibility of MT and TL/L curves, and the flexibility of MT curves correlated with flexibility TL/L curves. A negative correlation between flexibility of MT curves and AVT-T (thoracic apical vertebral translation) ( $$r$$ = − 0.2) was evidenced. No correlations between flexibility and sagittal parameters were observed. No strong correlation were observed between curve flexibility and age or skeletal maturity. A negative correlation between curve magnitude and flexibility at thoracic level was demonstrated. Furthermore, a weak positive correlation between flexibility of PT, MT and TL/L curves was observed.