Biomechanical Effects Of Intersegmental Stability Due To Cervical Laminectomy And Facetectomy

Object: The coordinate data of the vertebras were obtained from the CT scan images of a Chinese healthy 50th percentile adult male volunteer's cervical spine to establish a three-dimensional finite element model.Method: The coordinate data were converted into point cloud data and stored as ASCII file by using Mimics software. CATIA software was used to do preprocess and Geomagic software was used to establish the geometry model of the C0-C7cervical spine. The geometry model was meshed by using Hypermesh software. Mapped mesh method was used to do the mesh of cortical bone, trabecular bone, intervertebral disk, and ligaments, etc. Some material parameters were educed from other available material parameters by using proportion and function scale method.Result: The model has 22,512 solid elements and 14,180 shell/membrane elements. The cervical spine drop test results were used to validate the model. Conclusion: The comparison between test results and simulation results indicate that the model has good biofidelity and can be used to study the dynamic response and injury mechanism of the cervical spine in the crash accidents. Object: To investigate the biomechanical effects of intersegmental stability due to laminectomy, a three-dimensional nonlinear intact C1- C7 FE modelwas developed.Method: the modified FE modelwas set up to simulate laminectomy for intersegmental stability analysis. The inferior surface of C7 vertebra was constrained in all directions asboundary condition. Pure moment of 1. 5 Nm was applied over the top surface of C2 vertebra to simulate the movements of cervical spine under flexion, extension, lateral bending and axial rotation respectively.Results : there are apparent effects on intersegmental stability of cervical spine models due to laminectomy. A conclusion can be drawn that the intersegmental stability under all loading models ( flexion and extension, later bending, axial rotation) due to surgical procedure must be considered to making a biomechanical evaluation on multilevel laminectomy.When the extent of bilateral facetectomy has been more than 50%, intersegmental ranges of motion significiantly increased.Conclusion: Through three-dimensional finite element analysis, overmuch facetectomy will lead to cervical destabilization. The intrafixation or spinal fusion should be considered. Object: To investigate the biomechanical effects of intersegmental stability due to laminectomy,Method: The effects graded facetectomy on 10 fresh human cervical spine specimens ,were investigated. The graded facetectomy comprised 25%,50%,75%,100%resection.Six pure movements of 1.5Nm were applied in flexion ,extension,bilateral lateral blend ,bilateral axial rotation, ranges of motion were determined by stereophotography.Results : When the extent of bilateral facetectomy has been more than 50%, intersegmental ranges of motion significiantly increased.Conclusion: When the extent of bilateral facetectomy has been more than 50%,the intrafixation or spinal fusion should be considered.