Modelagem computacional da coluna torácica em idade infantil : avaliação da contribuição da cifose retificada no possível desenvolvimento da escoliose idiopática do adolescente

Abstract

The spine is a complex structure that is fundamental to the movement and the stability of the human body. Adolescent Idiopathic Scoliosis is a spinal deformity that affects the population aged between 10 and 16 years with no fully known cause. However, some authors link the development and/or progression of the disease to hypokyphosis in the thoracic region. The Finite Element Method has been widely used to investigate the biomechanical behavior of the spine and there are many studies that try to understand the mechanics of Adolescent Idiopathic Scoliosis. In this context, the present study proposes to numerically investigate, through the Finite Element Method, the biomechanics of the thoracic spine with child geometry for normal and rectified kyphosis conditions, under several loading conditions. For a better understanding of the subject, a literature review was prepared on the human spine, Adolescent Idiopathic Scoliosis, Fundamentals of Continuum Mechanics, Finite Element Method, and state of the art. To define the finite element mesh, a preliminary study of the T7­T8 spine functional unit was developed to study mesh convergence and quality. Then, finite element meshes were developed for the kyphosis and rectified segments. The vertebrae of the models were simulated as linear elastic materials and the intervertebral discs as isotropic hyperelastic materials. Despite knowing that intervertebral discs are non­linear structures with anisotropic behavior due to collagen fibers, preliminary studies carried out here demonstrated that the hyperelastic isotropic properties more adequately represent the proposed problems in terms of deformation. In addition to the physiological axial loading, flexion and extension moments were applied at the top of T5. Finally, the results showed greater instability of the rectified segment, especially when exposed to extension loads, with greater displacements and deformations. Furthermore, a more expressive displacement in the frontal plane was observed in the rectified segment, which intensifies the hypothesis that kyphosis rectification may be linked to the development and/or progression of scoliosis. Finally, despite the limitations inherent to this study, the computer simulation presented here is consistent with the literature data and appears to be a suitable tool for biomechanical studies of the spine.