A study of the radiologic predictors of curve flexibility in adolescent idiopathic scoliosis

Study Design: A study of flexibility of 101 idiopathic scoliosis antero-posterior radiographs. Objective: To discover if there are any parameters on plain antero-posterior radiographs that can predict the flexibility of scoliosis curves. Summary of Background Data: Previously the flexibility index, generated from fulcrum bending x-rays, has been shown to be an accurate measure of curve stiffness. Methods: Five postulated predictors of flexibility, measured on 101 immediate preoperative scoliosis radiographs, were compared with the flexibility index generated from fulcrum bending radiographs. Correlation between the 5 parameters and flexibility index was studied. Further analysis was performed to assess the significance of curve location in prediction of flexibility. Linear regression analysis was used. Results: Linear regression including all 5 predictors showed Cobb angle and age to be the only significant predictors of flexibility. When Cobb angle and age were analyzed with location (thoracic, thoracolumbar) this was also found to be a significant factor. Conclusions: Cobb angle, age, and curve location are useful predictors of flexibility on antero-posterior radiographs. This may aid preoperative planning in the out-patients department.