Research On Biomechanical Properties And Endplate Cutting For Robot-assisted Artificial Cervical Disc Replacement Surgery

Compared to traditional anterior cervical decompression and fusion, the artificial cervical disc replacement surgery has many advantages in the treatment of cervical disc degeneration and cervical spondylosis. But it is not widespread, mainly because the requirement of the doctor’s surgical experience is high, while the stand or fall of surgery is relative to the recovery of the degree of freedom of the patients’spine, and to make the artificial cervical maintain long-term effective play. Based on the System of Robot-assisted Artificial Cervical Disc Replacement Surgery (863Program), the research of cervical biomechanical characteristics by using the finite element method, can help the doctor understand the cervical biomechanical information, and reduce dependence on the operation experience. The research of the mechanical and temperature characteristics when the cervical endplate is cutting, can improve the operability and accuracy of robot-assisted artificial cervical disc replacement surgery for the clinical application.On the basis of analysis of the anatomical structure and biomechanical characteristics of the cervical spine, Through the CT data the three-dimensional cervical model is reconstructed, the triangular patch model is smoothed, the contour and zoning are meshed, the grille is constructed and surface is fitted, to get the cervical C5-C6segment vertebrae entity model and the assessment of physical reconstruction carries out by Gilad method. The finite element model of the facet joints included vertebrae, ligaments and intervertebral discs is established to research the contact analysis, and use the method of the load-displacement curve to validate the finite element model. In order to research the biomechanical characteristics by comparison, revise three-dimensional finite element model by reference to fusion and artificial cervical disc replacement operation, impose the same constraints and external load, observed and compared the normal group, changes in the cervical range of motion, ligament force of the fusion group, and the replacement group, vertebral stress distribution and disc stress distribution characteristics of the cervical spine biomechanics.In order to achieve the cutting simulation of end plate, physical process of the cervical end plate cutting is simplified, using plane orthogonal cutting model to simulate cervical end plate cutting. In the cutting simulation the large deformation simulation is solved by the ALE algorithm. Based on the anatomical structure and biomechanical characteristics of the cervical spine, the Johnson-Cook material constitutive model is built, the contact friction between the end plate and tool replaced by automatic single plane contact and using the formal definition of effective strain as the chip separation criterion. After the cutting parameters are set up for finite element dynamic simulation, the stress distribution, cutting force, surface residual stress and cutting temperature distribution in the end plate of the plane orthogonal cutting, and the change of cutting parameters are shown on the finite element model.Finally, the end-plate cutting experiments are carried out with the pig spine as experimental subjects, using parallel robot grinding platform, the ball screw platform, the six-axis force/torque sensors and other equipment. In the process of the experiments, the results of experiments are different when the sets of cutting parameters are different. Finally use the cutting force changing at any time to verify the simulation model and analysis the reasons to error.