title: Intraoperative three-dimensional correction during rod rotation technique.
abstract: METHODS
  A numerical study was conducted by simulating the Cotrel-Dubousset (CD) surgery.
  
  
  OBJECTIVE
  To quantify intraoperative correction during CD surgery.
  
  
  BACKGROUND
  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.
authors.affiliation: Laboratoire de Biomécanique, Ecole Nationale Supérieure des Arts et Métiers (ENSAM), UMR CNRS 8005, Paris, France. yoann.lafon@gmail.com
authors.forename: Yoann
authors.initials: Y
authors.lastname: Lafon
authors.forename: Virginie
authors.initials: V
authors.lastname: Lafage
authors.forename: Jean
authors.initials: J
authors.lastname: Dubousset
authors.forename: Wafa
authors.initials: W
authors.lastname: Skalli
mesh_terms: D000293:Adolescent; D000465:Algorithms; D001696:Biomechanical Phenomena; D001858:Bone Nails; D003198:Computer Simulation; D005260:Female; D020342:Finite Element Analysis; D006801:Humans; D007738:Kyphosis / Q000000981:diagnostic imaging / Q000503:physiopathology / Q000601:surgery; D008141:Lordosis / Q000000981:diagnostic imaging / Q000503:physiopathology / Q000601:surgery; D008159:Lumbar Vertebrae / Q000000981:diagnostic imaging / Q000502:physiology / Q000601:surgery; D008297:Male; D011300:Preoperative Care; D011859:Radiography; D012399:Rotation; D012600:Scoliosis / Q000000981:diagnostic imaging* / Q000503:physiopathology / Q000601:surgery*; D013123:Spinal Fusion / Q000295:instrumentation / Q000379:methods*; D013904:Thoracic Vertebrae / Q000000981:diagnostic imaging / Q000502:physiology / Q000601:surgery; D014143:Traction; D055815:Young Adult