Comparison of Standing Side Bending Using Biplanar Stereography and Fulcrum Bending for Flexibility Assessment of Adolescent Idiopathic Scoliosis

Background: The surgical treatment of adolescent idiopathic scoliosis (AIS) is influenced by factors such as skeletal maturity, curve magnitude, progression, and spinal flexibility. The assessment of spinal flexibility is crucial for surgical planning; supine bending radiographs are commonly used but there is no consensus on the optimal technique. Fulcrum bending radiographs (FBRs) have shown better prediction of post-surgery correction compared to supine bending radiographs. New radiological techniques allow a significant reduction in radiation exposure. This study aims to compare spinal flexibility assessment and radiation exposure between FBRs and standing side-bending radiographs (SSRs) using biplanar stereoradiography. Materials and Methods: Twenty-five consecutive AIS patients scheduled for surgery were included in this prospective cohort study. Exclusion criteria were non-idiopathic etiology, age younger than 12 years, and older than 18 years. Pre-surgery FBRs and SSRs were performed, and the Cobb angles were measured. Flexibility and correction rates were calculated. Dose-area products (DAPs) were recorded. Statistical analysis was conducted using the Wilcoxon signed-rank test and Spearman correlation. Results: The mean pre-surgery Cobb angle of the thoracic curve was 66.3°. The FBR was superior to SSR for assessing flexibility for thoracic curves and provided a better prediction for post-surgery correction. There was no significant difference in lumbar curves between FBR and SSR. The mean DAP for SSRs was 0.81 Gy*cm² compared to 3.42 Gy*cm² for FBR, indicating a lower radiation exposure using SSRs. Conclusions: FBRs are superior for flexibility assessment of thoracic curves in AIS and offers a better prediction of post-surgery correction compared to SSRs. However, FBR is associated with a higher radiation exposure.