Finite Element Modeling And Biomechanical Analysis Of Lumbar Vertebral Fractures

Lumbar spine is one of the most common sites of cancer metastasis.Fracture is a serious complication of cancer metastasis of lumbar spine,which can easily lead to the damage of biomechanical structure of lumbar spine and spine,and consequently shorten the survival time of patients.At present,most clinical cases rely on experience to judge the occurrence of fracture,and there is no consistent standard or controversy about the choice of operation timing or scheme.Therefore,this paper combines bio-kinetics with finite element method,establishes a three-dimensional finite element model of lumbar spine with fine cancer metastasis based on the mechanical calculation of lumbar spine skeletal muscle system in vivo physiological movement mode,and carries out multivariate numerical simulation study of lumbar spine fracture with cancer metastasis,in order to effectively reveal the effects of tumor parameters,skeletal parameters and physiological movement parameters on lumbar spine fracture.Influencing mechanism has important scientific significance and clinical value for innovating diagnosis and treatment means and technology and improving patients’quality of life.Based on the kinematics test of human lumbar spine,the whole body motion marking system was developed,and 11 kinds of physiological exercise tests were carried out on 5 subjects using infrared motion capture system.Based on the results of kinematics test,11 kinds of physiological exercises were simulated on Opensim platform,and the time history curves of interaction force and moment between lumbar joints were obtained.The results of comparative analysis show that the joint forces and moments between L2-L3 lumbar joints calculated in this paper are similar to the literature data.Therefore,they can be used in subsequent finite element simulation.Load driven.Based on magnetic resonance imaging（MRI）,a finite element model of L3-L5lumbar spine was established,which included the third lumbar spine,the fourth lumbar spine,the fifth lumbar spine,two intervertebral discs（considering annular tissue）and seven ligaments（72 ligaments）.The comparative simulation analysis of joint freedom of motion of forward bending,backward extension,lateral bending and axial rotation was carried out,and the model was further modified.Finally,the simulation results show that the three-dimensional finite element model of the lumbar spine established in this paper is in good agreement with the literature data.The model is reasonable and effective,and can be used in the biomechanical study of lumbar vertebral fracture with cancer metastasis.Based on the established three-dimensional finite element model of lumbar spine,the fourth lumbar spine was selected and implanted into the tumor model.Orthogonal regression experiments were designed for three factors:tumor size,tumor shape and bone mineral density.The simulation experiments were carried out.The effects of tumor size,tumor shape and bone mineral density on the risk of lumbar spine fracture were analyzed.Finally,in vivo physiological movement based on lumbar spine fracture was obtained.Multivariate numerical model and mathematical regression equation of lumbar vertebral fracture with cancer metastasis under state.The regression equation and analysis results under the corresponding motion state are as follows.（1）Under the forward bending motion mode,the regression equation is as follows:^?y（28）496.876-12.163Z₁（10）0.118Z₁²-.3058Z₂（10）.0009Z₂²（10）0.141Z₁Z₂The results showed that the size of tumors was the most important factor affecting vertebral fracture,followed by the location of tumors,while bone mineral density had less influence on vertebral fracture.（2）Under the extended motion mode,the regression equation is as follows:^?y（28）111.277（10）.0006Z₁²-.0071Z₂-.0206Z₃The results showed that the stress near the conical foramen of vertebral bone was the greatest under the mode of awaiting extension,and the location of tumors was the most important factor affecting vertebral fracture,while the bone mineral density was also the most important factor,while the size of tumors had less influence.（3）Under the lateral bending motion mode,the regression equation is as follows:^?y（28）219.038-.3488Z₁（10）.004Z₁²-.1301Z₂（10）.0004Z₂²（10）.0042Z₁Z₂The results show that the stress distribution of cortical bone is more uniform and the stress of cancellous bone is larger in lateral bending motion mode.The size of tumors has a greater impact on vertebral fracture,followed by the location of tumors,while the influence of bone mineral density is smaller.（4）Under the mode of axially rotating motion,the regression equation is as follows:^?y（28）-10.373-.0349Z₁-.0009Z₁²（10）.0374Z₂-.0001Z₂²（10）.0084Z₃-.0015Z₁Z₂-.0003Z₁Z₃The results showed that the location of the tumors in the axial rotation mode had a greater impact on the vertebral fracture,followed by the size of the tumors,and finally the bone mineral density.