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Analysis of Idiopathic Scoliosis Progression by Using Numerical Simulation

Drevelle, X., MSc*; Lafon, Y., PhD*; Ebermeyer, E., MD; Courtois, I., MD; Dubousset, J., MD*; Skalli, W., PhD*

doi: 10.1097/BRS.0b013e3181cb46d6
Deformity
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Study Design. 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.

Summary of Background Data. 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.

Conclusion. 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.

Mechanisms of idiopathic scoliosis progression were investigated by using a patient-specific numerical model. For 12 scoliotic patients and 6 asymptomatic subjects, the combined effect of gravity, anterior spinal growth, and a decrease of disc’s stiffness were simulated. Scoliosis-like deformity progression was obtained only for some preexisting curvatures.

From the *Arts et Metiers ParisTech, CNRS, LBM, Paris, France; and †Unite Rachis, CHU - Hopital Bellevue, Saint-Etienne, France.

Acknowledgment date May 26, 2009. Revision date: October 14, 2009. Acceptance date: October 15, 2009.

The device(s)/drug(s) is/are FDA-approved or approved by corresponding national agency for this indication.

Foundation funds were received in support of this work. No benefits in any form have been or will be received from a commercial party related directly or indirectly to the subject of this manuscript.

Address correspondence and reprint requests to Xavier Drevelle, MSc, Arts et Metiers ParisTech, CNRS, LBM, 151, Boulevard de l’Hôpital 75013 Paris, France; E-mail: xavier.drevelle@gmail.com or wafa.skalli@paris.ensam.fr

© 2010 Lippincott Williams & Wilkins, Inc.