Establishment And Biomechanical Study Of Minimally Invasive Spinal(Lumbar Vertebra) Fusion System

Objective: to analyze the changes of intervertebral motion and the stress changes of lumbar vertebra and intervertebral disc in the lumbar minimally invasive fusion system and the lumbar pedicle screw rod system,and to study the biomechanical properties of this new minimally invasive fusion technology.Methods: using CT scanning data of a healthy adult male volunteer,the finite element model of l4-l5 was established using Mimics19.0 software,Geomagic Design X64,Hyper Mesh12.0 software,and CATIA V5 R20 software.The finite element models of lumbar minimally invasive fusion system and lumbar pedicle screw system were established by using CAD technology.Then,the activity degree of lumbar segmental flexion,extension,lateral flexion and rotation motion was measured when specific preload and torque were applied to the lumbar spine model,and the results were compared with those in the literature to determine whether the model was effective.The lumbar finite element model of lumbar fusion system and lumbar finite element model assembly and pedicle screw system were established,and the same specific preload and torque were applied to the two models,respectively,to calculate the motion degree of lumbar segment flexion,extension,rotation and lateral flexion,as well as the lumbar spine,internal plant and intervertebral disc stress.Results: 1.A three-dimensional finite element model of the normal lumbar spine(l4-l5)was established,and the shape was the same as the entity.2.After implantation and fixation of the lumbar minimally invasive fusion system,the anterior flexion of the l4/5 segment decreased by 84.0%,the posterior extension activity decreased by66.7%,the lateral flexion activity decreased by 70.3%,and the rotational activity decreased by 87.2% after the reconstruction of the lumbar minimally invasive fusion system.After pedicle screw fixation,anterior flexion activity decreased by 78.1%,posterior extension activity decreased by 75.0%,lateral flexion activity decreased by97.2%,and rotational activity decreased by 93.6%.3.The stress concentration of intervertebral disc in the posterior(compression side)of normal lumbar spine,minimally invasive fusion of lumbar spine and posterior extension of lumbar pedicle fusion was 4.1MPa,1.5 MPa and 1.6MPa,respectively.4.The contact stress between the lumbar vertebrae and the minimally invasive fusion system of the lumbar spine was as follows: the contact stress between the spinous process and the implant was the minimum at 8.85 mpa when the spine was extended;In lateral curvature,the contact stress of spinous process and endophyte was followed by 15.03 mpa.At torsion,the contact stress between the spinous process and the endophyte was the highest,which was 22.47 mpa.Conclusion: the three dimensional finite element model of lumbar spine(L4-L5)has been verified to be effective and can be used for biomechanical experiments.Changes in lumbar model activity,vertebral body and disc stress by the lumbar interbody fusion system and pedicle screw fixation system were the same.The maximum contact stress between the lumbar fusion system and the vertebral spinous process was significantly reduced compared with the inter-spinous process distraction device in the literature.The new minimally invasive fusion system of the lumbar spine has good biomechanical properties,providing new ideas and techniques for the optimization of minimally invasive treatment of degenerative diseases of the lumbar spine.