| In contemporary society,with the continuous increase of professional labor tasks such as computer engineers and desk workers,the incidence of cervical spine diseases was on rise,and presents a trend of professionalism and younger age.Cervical spondylosis often caused by intervertebral disc degeneration and vertebral osteophyte compression on the nervous root,these lesions parts are closely related to cervical biomechanics.Medical researchers urgently need to know the influence of mechanical factors on the inducing mechanism of cervical spondylosis.In addition,the anterior fixation system was often used in anterior cervical discectomy and fusion,which has the advantages of preventing segmental kyphosis and maintaining immediate stability after surgery,and has been rapidly developed in surgery.However,due to the mechanical performance of the fixation system,some complications caused by screw loosening and fracture,failure of the cervical plate,and failure of bone graft bridging.There is still no consensus on the ideal fixation device design for increasing fusion rate and reducing complications.In this paper,we through the human neck in vitro experiment compared with literature to verify the finite element model.The objective of this paper is the mechanism of cervical spondylosis induced factors of mechanics,and explore the profile design and the number of screw internal fixation system change of equipment of the influence of the cervical spine biomechanics characteristics.This paper for clinical prevention of cervical disease,and anterior fixation system designed to provide basic data and important mechanics basis.Firstly,an in vitro experiment was designed.Capturing the reflective markers pasted on the volunteers’ necks of the dynamic response data of flexion,left/right bending and left/right rotation physiological motion patterns,were obtained by using a three-dimensional motion capture system.The result shows that the displacement of the upper cervical spine was significantly higher than that of the lower cervical spine.There was a certain symmetry in the flexion and rotation of the volunteers’ necks,and the experimental data showed a consistent trend of results.A cervical C1-C7 finite element model of was established based on the cervical CT data of volunteers who participated in vitro experiments.Through the simulation results of the model were compared with the motion data of cervical spinous process obtained from in vitro experiments and data from previous literatures,so as to verify the validation of this model.The results show that the simulation data in this paper are within the error of experimental data and literature data,and the validiation of the established model was verified.Therefore,the assumptions and simplifications considered in the modeling process of this paper are reasonable and the model can be used for the follow-up study of cervical biomechanics.The finite element model established by the above work was divided flexion angle20°,25°,30°,35°,40° and 45° by applying different torques.The micro-strain of vertebral and intervertebral disc stress under different flexion angles were analyzed to explore the potential mechanical influence of flexion angle on cervical spondylosis.The results showed that compared with 20°,the microstrain of cervical spondylosis prone site increased by 119% on average when flexion 45°,and the overall bone mass may have an increasing trend.The stress on the disc increases by an average of 70%.Excessive load may accelerate the process of degeneration.Based on the intact cervical finite element model,the triangle anterior cervical plate(TACP)and quadrilateral anterior cervical plate(QACP)implantation models were reconstructed.The expected biomechanical effects of the two internal fixation systems under different motion patterns were compared.The result shows that the maximum stress of the TACP screw and cervical plate during extension was 51% and12% higher than QACP,respectively.The stress of the endplate and the cage displacement were the highest in QACP,which were 81% and 12% higher than that of TACP,respectively.The stress of the endplate and the cage displacement were highest in QACP,which were 81% and 12% higher than that of TACP,respectively.In addition,the average stress ratio of TACP cage-graft to QACP was 11% higher.Compared with the intact model,the range of motion(ROM)of adjacent segments of TACP and QACP increased by 4.3% and 10.8%,respectively.The stress on the screw hole of TACP was40% less than that of QACP on average.Finite element analysis shows that compared with QACP,TACP had potential advantages in reducing the cage subsidence,reducing the degeneration of adjacent segments,reducing the risk of screw hole vertebral injury and improving the fusion effect.The results of the present study may help to explain the difference in mechanical behavior caused by the difference in the profile of the fixation plate and the number of screws,and provide a new idea and theoretical basis for the design of the anterior internal fixation system. |
