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Objective To investigate cervical biomechanics and secondary pathological changes of the calcific posterior longitudinal ligament by 3D finite element analysis.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 the 3D reconstruction with MIMICS (Version 12) and mesh with HYPERMESH 10.0 software and post-processing software for the calculation of LS-DYNA3D 971 (LSTC, USA) .Model development andsimulation were performed on the Dell Power Edge 12G M420 blade servers, which C7 was fixed, and the loading moment were 3 N·m in flexion, extension and axial rotation motions respectively.Compared with the normal by changing the parameters of the posterior longitudinal ligament material properties in lateral bending, flexion, axial rotation motion.Results After changing the parameters of the posterior longitudinal ligament material properties, in flexion, the maximum stress of the intervertebral disc decreased by 6%.In extension the maximum stress of the nucleus decreased by 11%, the maximum stress of facet joints increased by 15.7%.In rotation, respectively, the maximum stress of intervertebral disc reduced by 24%, the maximum stress concentrated at the direction of rotation in C4/5 fiber ring;the maximum stress of the nucleus reduced by 25%, and the position transferred from C2/3 to C6/7, the maximum stress of the facet joints decreased by 10%.Conclusions We can know that after the PLL harden the distribution of the mechanical system will be changed by using FEM.In flexion and rotation movement the PLL will carry more power after hardening, which may exacerbate existing disease or cause secondary injury.Moreover, the maximum stress position in extension is transferred to vertebral small joints, which increases the possibility of secondary injury to vertebra small joint.