Finite Element Analysis Of The Cervical Biomechanics:in Material Properties Of Posterior Longitudinal Ligament

Objectives:1. To develop3-D finite element models of normal and material properties changed of posterior longitudinal ligament cervical spine (C1～C7) with detailed anatomical structure, which can be used to biomechanical investigation of cervical spine.2.Investigate the induration posterior longitudinal ligament effect of cervical biomechanics and secondary pathological changes. Materials and Methods: Sectional images of cervical spine (C1～C7) were obtained from CT scans of a healthy adult male. The FEM of cervical spine(C1～C7) was developed with the cervical spine CT images by the3D reconstruction with MIMICS (Version12)software and mesh with HYPERMESH10.0,and post-processing software for the calculation of LS-DYNA3D971. Model development and simulation performed on Dell Power Edge12G M420blade servers. Validate the model by calculating the flexion and extension, lateral bending, axial rotation range of motion under loaded conditions (ROM) and disc displacement, and results were compared with experimental model analysis of past scholars and finite element model(FEM) to analyze its compliance with the degree. By changing the parameters of the posterior longitudinal ligament material properties, the establishment of appropriate cervical C1～C73-dimensional finite element model. In lateral bending, flexion, axial rotation movement, biomech-anical comparison of normal and posterior longitudinal ligament after changing the material properties of FEM. Results:1.A3D finite element model of normal cervical spine (C1～C7) has been constructed and validated successfully. The range of motion (ROM)tested in flexion and extension, lateral bending, and axial rotation correlated well agree with the results by other scholars. The FEM of cervical spine (C1～C7) can be used to biomechanical investigation of cervical spine. In this basis, the FEM of the induration posterior longitudinal ligament was established.2.In flateral movement, compared with the IPLL, the intervertebral disc maximum stress, the nucleus pulposus maximum stress, maximum stress on the vertebral, vertebral endplate maximum stress, small joints of maximum stress and range of motion, no significant difference.3.In extension movement, the nucleus maximum stress decreased by11%, the facet joints maximum stress by15.7%of IPLL.4. In flexion movement the Cervical FEM shows intervertebral disc maximum stress is reduced by6%after the PLL hardened, no change in location.5.In rotation, repectively,intervertebral disc maximum stress is reduced by24%, the maximum stress concentration at the C4/5rotate side; nucleus maximum stress is reduced by25%, and the position from C2/3to C6/7; vertebral maximum stress decreased by5%; facet joints maximum stress decreased by10%. No significant change in endplate stress. Conclusions:1. After induration of the posterior longitudinal ligament, flexion motion, intervertebral disc maximum stress is reduced and in rotation, the intervertebral disc maximum stress, the nucleus maximum stress, the vertebral maximum stress,the facet joints maximum stress are also reduced. From the biomechanical aspects proved hardened after posterior longitudinal ligament in flexion and rotation movement, will bear more force, aggravated existing disease or cause secondary damage.2.In Extention movement, intervertebral disc maximum stress is reduced in IPLL, no significant changes in the nucleus maximum stress,yet the facet jointsmaximum stress increased.From the biomechanical aspects it is indicated IPLL will change the site of the occurrence of the maximum force and will consiquently cause facet joint osteoarthritis in the future.