Experimental modeling of burst fractures of the thoracolumbar spine

V.A. Radchenko, K.A. Popsuyshapka, M.Yu. Karpinsky, E.D. Karpinska, S.A. Teslenko

Abstract


Background. According to various authors, burst fractures of lower thoracic and lumbar spine are the most common among the whole number of injuries and take 20–40 % of all spine traumas. The purpose of the study was to explore the biomechanical characteristics of kyphosis that develops under the influence of the axial compressive load along the entire spine, depending on the degree of damage to the spinal segment. Materials and methods. Physical model of burst fracture of Th12 vertebra was realized on anatomic preparations of blocks of vertebral segments of the animal (pig). In the first group, bone and ligamentous structures were saved. In the second group, up to 50 % of the vertebral body was destroyed. In the third group — all the body and two adjacent spinal disks. In the forth group — 100 % of the body, disks, archs, ligaments and joints. Results. Depending on the degree of destruction of the functional spinal unit Th12, general elastic modulus of the model is reduced. It happens due to the loss of the support function of the elements of the segment. The biomechanical model with nondestructive structures for all kinds of loads has the maximum elastic modulus. With destruction of the anatomical structures and with increasing stresses, the elastic modulus decreases progressively. Reduction of the elastic modulus to the limit values was achieved by samples with destroyed vertebral body, disks, posterior structures at medium and maximum loads. This type of model is the most unstable, with no elastic modulus. Samples with damage to the vertebral body by 50 % and the disk and samples with 100 % damage of the vertebral body and 2 disks have a certain level of elastic modulus that depends on the load and degree of destruction, i.e. they are stable samples with regard to the value of the primary deformation. Conclusions. By increasing the amount of destruction of the spinal motion segment Th12, the value of axial compression of the model under compressive load was significantly increased for all values of the compressive force. Depending on the degree of destruction of the spinal motion segment Th12, the modulus of total deformation of the model is reduced due to loss of the support function of the segment elements. Depending on the degree of damage and the applied load values, there are both elastic and plastic deformation types. Violation of the strength of the model was at the stage of 50% destruction of the vertebral body and superjacent intervertebral disc, at loading intensity of 100 N. With increasing degree of destruction, the sample loses its ability to withstand the increasing loads, as evidence by a decrease of the overall deformation modulus of the samples.

Keywords


spine; intervertebral disc; elastic modulus

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DOI: https://doi.org/10.22141/1608-1706.2.18.2017.102558

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