Intraoperative Three-Dimensional Correction During Rod Rotation Technique

Study Design. A numerical study was conducted by simulating the Cotrel-Dubousset (CD) surgery. Objective. To quantify intraoperative correction during CD surgery. Summary of Background Data. Very few methods have been reported in literature to analyze the effect of intraoperative surgical gestures, and none considers the three-dimensional correction of the entire spine during the main surgical gestures. Intraoperative frontal radiographs limit analysis to two-dimensional correction, and movement tracking devices focus the kinematics study of specific vertebrae in the instrumented area only. Methods. This study included 20 patients, mean age 15 years, with severe idiopathic scoliosis treated by CD surgery. A patient-specific finite-element model (T1-L5 and pelvis), based on preoperative stereo-radiography and flexibility test radiographs, was constructed for each patient. An automated algorithm simulated all the main steps of the CD surgery. For each step, vertebral kinematics was exported to compute the evolution of various clinical parameters. Coherence of the simulations was evaluated by comparing the virtual postoperative spinal configuration with postoperative in vivo data. Results. The CD surgery affected the vertebral levels inside but also outside the fused spinal area, in a three-dimensional complex kinematics. Every intraoperative maneuver contributes to scoliosis correction. The second rod insertion, focused on the apical vertebra, leading to a global modification of all the curves. Conclusions. The automated patient-specific simulation of CD surgery may improve our understanding of surgical biomechanics. Therefore, it could increase the relevance of preoperative surgery planning.