Abstract
Adolescent idiopathic scoliosis (AIS) is a three-dimensional (3D) deformity of the spinal column in pediatric population. The primary cause of scoliosis remains unknown. The lack of such understanding has hampered development of effective preventive methods for management of this disease. A long-held assumption in pathogenesis of AIS is that the upright spine in human plays an important role in induction of scoliosis. Here, the variations in the sagittal curve of the scoliotic and non-scoliotic pediatric spines were used to study whether specific sagittal curves, under physiological loadings, are prone to 3D deformation leading to scoliosis. To this end, finite element models of the S shaped elastic rods, which their curves were derived from the radiographs of 129 sagittal spinal curves of adolescents with and without scoliosis, were generated. Using the mechanics of deformation in elastic rods, this study showed that the 3D deformation patterns of the two-dimensional S shaped slender elastic rods mimics the 3D patterns of the spinal deformity in AIS patients with the same S shaped sagittal spinal curve. On the other hand, the rods representing the non-scoliotic sagittal spinal curves, under the same mechanical loading, did not twist thus did not lead to a 3D deformation. This study provided strong evidence that the shape of the sagittal profile in individuals can be a leading cause of the 3D spinal deformity as is observed in the AIS population.
Highlights
The mechanics of deformation in elastic rods are explored experimentally and analytically[26,27,28,29]
The study steps include: 1- classification of 126 scoliotic 3D spinal curves34,35, 2- developing the finite element models of the curved elastic rods using the S shaped sagittal spinal curve of the scoliotic cluster centers and the average of three non-scoliotic spines. 3- Comparing the patterns of deformation between the actual spinal deformity in the patient subtypes and the simulated curved rods deformations
Concepts in mechanics of elastic rods were used to show that the variations in the sagittal curve relate to the 3D deformation patterns of the spine in Adolescent idiopathic scoliosis (AIS)
Summary
The mechanics of deformation in elastic rods are explored experimentally and analytically[26,27,28,29] These concepts have been successfully explained the physics of various topological transformation in DNA and proteins (e.g., from a loop to a twisted loop)[30,31,32]. As these two axial projections (Fig. 1) were associated with different sagittal curves in the scoliotic classification[34], the question was raised that whether the variation in the sagittal curves of the pediatric spine dictates the patterns of spinal deformation and can be the leading cause of the 3D spinal deformity i.e. scoliosis. It was hypothesized that the patterns of 3D deformation of 2D S shaped elastic rods (spine sagittal profiles) relate to the 3D patterns of the spinal deformity in the AIS patients with the same sagittal curves
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