Our aim in this prospective radiological study was to determine whether the flexibility rate calculated from radiographs obtained during forced traction under general anaesthesia, was better than that of fulcrum-bending radiographs before corrective surgery in predicting the extent of the available correction in patients with idiopathic scoliosis. We evaluated 33 patients with a Cobb angle >
60° on a standing posteroanterior radiograph, who had been treated by posterior correction. Pre-operative standing fulcrum-bending radiographs and those with forced-traction under general anaesthesia were obtained. Post-operative standing radiographs were taken after surgical correction. The mean forced-traction flexibility rate was 55% ( Radiographs obtained during forced traction under general anaesthesia were better at predicting the flexibility of the curve than fulcrum-bending radiographs in curves with a Cobb angle >
60° in the standing position and may identify those patients for whom supplementary anterior surgery can be avoided.