Biomechanical Study Of Rabbit Vertebral Body Injury

Since the beginning of the 21 st century,China's economy has developed rapidly,people's lives have undergone qualitative changes,people's travel speed has become faster and faster,and urban buildings have become more and more high,but the human damage caused by people has also increased year by year.According to incomplete statistics,traffic injuries and fall injuries have become the main form of injury,and spinal injuries caused by traffic accidents and falls have become the main cause of spinal injuries.From the database of spinal cord injury in China,it can be found that the proportion of spinal injury caused by falling is 24%,and the spinal injury caused by traffic accident is 44%.Therefore,it is important to study the damage characteristics of the spine under impact load,and it can also provide a biomechanical basis for damage protection and repair of the spine.Therefore,the research work of this paper is carried out.The main research content is to obtain the damage characteristics and regularity of rabbit spine single vertebral body under impact load by finite element analysis and experimental measurement.The specific research contents of this paper are as follows:(1)CT scan images based on rabbit spine were established by three-dimensional reconstruction method and reverse engineering principle using medical image modeling,geometric modeling and finite element modeling and analysis software(Mimics,Geomagic Design,HyperMesh and Abaqus).The geometric and finite element model of the rabbit single vertebral body T12.(2)The validity of the established single-vertebral finite element model of T12 was validated by the same fixation and loading method as the previous single-vertebral static compression experiment.By comparing and analyzing the load-time curve obtained by static compression finite element simulation and the load-time curve obtained by static compression experiment,it was found that the finite element simulation results were in good agreement with the experimental results,thus verifying the validity of the finite element model.(3)A finite element model of a single vertebral body T12 was established.First,the sensitivity of the mesh quality was analyzed by Abaqus and the appropriate number of meshes was selected.Then,the effects of different impact rates and material property changes(to characterize patients with different degrees of osteoporosis)on the stress distribution of the vertebral body were simulated and analyzed.(4)A finite element model of another single vertebral body L1 of the same spine was established to analyze the difference in mechanical properties of different single vertebral bodies T12 and L1 under the same working conditions.(5)A single vertebral body of T12 and L1 was obtained by dissecting three New Zealand white rabbits of 191-day rabbit age.The single vertebral body was subjected to an impact test on an Instron CEAST 9350 test machine to obtain the mechanical damage characteristics of the single vertebral body under impact.Through finite element simulation and analysis and experimental data processing and analysis,the following conclusions can be obtained:(1)Through finite element analysis,it could be found that different numbers of meshes have certain influence on the calculation results of stress and other parameters of single vertebral body,especially the displacement.When the number of grids was 74224,the results of finite element analysis were much more reasonable than those of other grids.(2)At different impact rates,by analyzing the overall displacement-time curve of a single vertebral body,it could be concluded that the vertebral material was the same as most brittle materials,and when subjected to a vertical load,a 45 degree angle of failure could occur.And the maximum stress value was mainly concentrated at the two ends of the single vertebral body,and the direction of stress transmission was consistent with the trend of the trabecular bone.(3)By assigning five different material properties to the finite element model to simulate the mechanical properties of five different degrees of osteoporosis,it was found that the lower the bone density,the worse the mechanical properties,and the fractures were also prone to damage.The determination of material properties was also an important part of finite element analysis.It was best to have corresponding experiments to determine the material parameters.The reference material parameters could only be used as a method to learn,but could not guarantee the accuracy of finite element analysis results.(4)The load-time curve of a single vertebral body was obtained by the drop impact dynamic impact test of a single vertebral body.It could be found that the curve consists of multiple peaks,mainly because the structure of the vertebrae is extremely complex,and the material of the vertebrae is heterogeneous,anisotropic,and porous.The process of single vertebral destruction was mainly divided into two stages,the first stage was the destruction of the lower articular process and the vertebral arch,and the second stage was the destruction of the vertebral body.The results of this study are of great significance for understanding the damage mechanism of the burst fracture caused by the impact load and the mechanical properties of the single vertebral body.It also has certain reference value for the evaluation,treatment and protection of spinal injury in clinical medicine.