title: Analysis of idiopathic scoliosis progression by using numerical simulation.
abstract: METHODS
  The mechanisms of idiopathic scoliosis progression were investigated through a patient-specific numerical model.
  
  
  OBJECTIVE
  To explore the combined effect of gravity, the decrease of intervertebral discs' stiffness and the anterior spinal growth on scoliosis progression, by using a numerical simulation, to better understand mechanisms of scoliosis progression.
  
  
  BACKGROUND
  Eighteen adolescents (12 girls, 6 boys) with an average age of 10.5 years (range, 7-13) were divided into 2 groups: 12 mild scoliotic patients with thoracolumbar curves and 6 asymptomatic subjects.
  
  
  METHODS
  Accurate 3-dimensional reconstructions of the spine were performed from biplanar radiographs. A patient-specific validated finite element model was used. Four configurations were simulated for each patient: the first configuration with the spine under gravity, the second one under gravity with a decrease of disc's mechanical stiffness, the third one under gravity with anterior vertebral growth, and the last one with combination of the 3 previous configurations.
  
  
  RESULTS
  Gravity loads resulted mainly in a vertebral lateral deviation of the curve without axial rotation for all patients with mild scoliosis. Anterior vertebral growth with gravity induced both lateral deviation and axial rotation. This phenomenon was amplified when the mechanical properties of discs were decreased. None of these simulations initiated a scoliosis-like deformity for asymptomatic subjects.
  
  
  CONCLUSIONS
  For preexisting spinal curvature, an anterior spinal growth combined with gravity and a decrease of disc's mechanical stiffness could lead to a progression of scoliosis. Biomechanical factors could be secondary after initial deformation.
authors.affiliation: Arts et Metiers ParisTech, CNRS, LBM, 151 Boulevard de l'Hôpital, Paris, France. xavier.drevelle@gmail.com
authors.forename: X
authors.initials: X
authors.lastname: Drevelle
authors.forename: Y
authors.initials: Y
authors.lastname: Lafon
authors.forename: E
authors.initials: E
authors.lastname: Ebermeyer
authors.forename: I
authors.initials: I
authors.lastname: Courtois
authors.forename: J
authors.initials: J
authors.lastname: Dubousset
authors.forename: W
authors.initials: W
authors.lastname: Skalli
mesh_terms: D000293:Adolescent; D001696:Biomechanical Phenomena / Q000502:physiology; D002648:Child; D005260:Female; D020342:Finite Element Analysis; D006112:Gravitation; D006801:Humans; D021621:Imaging, Three-Dimensional / Q000379:methods*; D007403:Intervertebral Disc / Q000000981:diagnostic imaging / Q000254:growth & development / Q000503:physiopathology; D008297:Male; D008953:Models, Anatomic; D011859:Radiography / Q000379:methods*; D016059:Range of Motion, Articular / Q000502:physiology; D012399:Rotation; D012600:Scoliosis / Q000000981:diagnostic imaging* / Q000473:pathology / Q000503:physiopathology; D013131:Spine / Q000000981:diagnostic imaging* / Q000254:growth & development* / Q000503:physiopathology; D013314:Stress, Mechanical; D016474:Weight-Bearing / Q000502:physiology