The Analysis and Comparison of Adjacent Segment Degeneration of the Finite Element Caused by Three Posterior Lumbar Fusion Style
|School||Zunyi Medical College,|
|Keywords||Dimensional finite element Adjacent segments Lumbar Fusion Degeneration Lumbar instability|
Objective:A three-dimensional finite element model of L3-L5 is developed, Simulation of three Posterior lumbar fusion, analysis and comparison of fusion after the stress adjacent segment changes, from the mechanics of three posterior lumbar spinal fusion on the interpretation of adjacent segment degeneration after the speed of different mechanisms.Methods:To develop such FEN,a set of CT images are gotten from clinic.Based on the CT images,the outline are extracted by Mimics and then these outline are transformed into FEM software Abaqus to establish the 3D-FEM of a Chinese L3-L5 lumbar motion segment.All solid components,including cortical and cancellous bone,endplates,anulus ground substance are meshed by 10-node tetrahedron elements.To appropriately model the changing areas of contact of fact articulating surface with increments in loading,fact articulation were simulated by frictionless surface contact. Seven different ligaments are used to simulate approximately the ligamentous structure in the motion segment,the attachment points of these ligaments to the bone prominence are chosen based on anatomy to mimics anatomic observations as closely as possible.The mechanical properties of ligaments are assumed to be nonlinear and derived from experimental study of literatures.In the normal model simulation of L4-5 segment of the three commonly used clinical laminectomy and fusion or posterior fusion and internal fixation type 1, total laminectomy plus posterior intertransverse process fusion.2, total laminectomy plus posterior intertransverse fusion with pedicle screw fixation.3, total laminectomy posterior interbody fusion Cage implantation of pedicle screw fixation.A compressive load of 500N is applied uniformly to all nodes of top surface of the L3 body. A pure moment of 15Nm is applied on top of the front、poster left and right of surface of L3 vertebral body to mimics loading conditions in the mechanical testing of motion segment,and compared with each other.Result:This study shows the importance of preserving ligaments to prevent rotational instabilities for motion segment after laminectomy. Compression and flexion induce disc bulging in anterior region,whereas extension and lateral bending induce disc bulging posteriorly and posterolaterally. In the three surgical model, the transverse process fusion and internal fixation of non-disc stress no significant change in posterolateral fusion and internal fixation, interbody fusion and internal fixation followed by intervertebral disc stress significantly increased.the virtual sampie of small jiont lateral bending and axial state, the interbody fusion and internal fixation and posterolateral fusion and internal fixation of small joints stress was significantly higher than non-intertransverse process fusion and internal fixation, in which internal fixation and interbody fusion and posterolateral fusion than fixation was significantly higher.Conclusin:A variety of lumbar fusion and internal fixation due to increased stiffness of fusion segments, or the applied load in the lumbar motion segment when the adjacent intervertebral disc, facet joint stress significantly increased, adjacent segment degeneration and the possibility of instability at the posterolateral fusion fixation, interbody fusion and internal fixation in order to increase. No significant changes between the transverse process fusion. So the line posterior lumbar fusion, such as adjacent segment degeneration has been the performance of the line as far as possible intertransverse fusion, to increase the fusion rate, followed by fixation with posterolateral fusion line to avoid line interbody fusion fixed. To improve surgery and reduce or avoid adjacent segment disease.Posterolateral lumbar interbody fusion and internal fixation in patients compared with pure intertransverse fusion, guide the activities of patients after exercise to reduce the extension, lateral bending and torsion of these three the number and intensity of active state, to reduce the incidence of adjacent segment disease.