Evaluation of Curve Flexibility Using Scoliotic Spines Generated From a Generic Spine Model

Curve flexibility is critical for preoperative planning in adolescent idiopathic scoliosis (AIS) as it guides surgical strategy and selection of appropriate release manoeuvres. Although finite element (FE) modelling has been widely used to investigate spinal biomechanics, its application to spinal flexibility assessment remains underexplored. This study developed AIS FE models to evaluate the effects of sequential spinal release techniques on curve flexibility under fulcrum bending radiographs (FBR) and supine traction radiographs (STR). A validated generic adolescent spine model was deformed using a displacement-based shaping approach to generate three representative AIS spines. Curve flexibility was assessed computationally under simulated FBR and STR conditions. Five sequential surgical release manoeuvres were then simulated. To estimate the required traction force for STR, three cases of AIS patients were analysed to determine the traction force that reproduced the clinically reported flexibility. Three generic-derived scoliotic spines and three patient-based curves were successfully generated. The effective STR traction force was estimated as 376.6 N. For curve flexibility assessments, disc release produced the largest flexibility gain, while facetectomy produced the least improvement. Under STR, flexibility increased progressively with stepwise releases. Under FBR, flexibility responses were more curve-type dependent. This study provides a computational approach for developing AIS models, assessing AIS curve flexibility and comparing spinal release strategies. Generic-derived scoliosis models enabled controlled curve flexibility comparisons across various curve types and surgical manoeuvres; thus, they may assist in eliciting answers to common clinical questions and support preoperative planning.