The Establishment And Appliment Of The Three-Dimensional Finite Element Model Of Cerical Spine

Objective (1) To establish the cervical three-dimensional finite element model(C4/5/6) and it will be used for clinical study. (2) To discuss the alternation of cervical biomechanics after the degeneration of cervical intervertebral disc and the influence of degeneration to cervical instability. (3) To discuss the biomechanics alternation of the adjacent Functional Spinal Unit (FSU) after the intervertebral fusion and the influence of fusion to cervical degeneration. (4) To discuss the cervcal range of motion(ROM) after the atificial intervertebral disc replacement and the application of FEM in design of artificial cervical intervertebral disc.Methods (1) We selected a heathy adult male volunteer. He was checked by radiative and clinical examination and was proved that he have no any spinal disease. Then his cervical vertebral was scaned by Siemens Somatom Sensation 16 with 0.75mm thickness. We could get the data of CT imaging and input the data with DICOM format. After the CT imaging was processed by Materialise Mimics we can achieve the superficial 3D imaging and its boundary coordination. The 3D imaging was processed by Unigraphics NX to become a 3D entity. And according to the measured data we made the the 3D entity of C₄/5, C₅/6 intervertebral disc. Then these 3D entities was meshed by the FEA software — ANSYS 8.1. Different material was assigned different mechanical parameter, and we created a cervical three-dimensional finite element model(C₄/5/6). After setting the boundary ,under the 45N preload the model is loaded the 2.0N moment to simulate the flexion/extension, left/right bending and rotating. The relationship of the movement and displacement will compare withthe results of experiment in vitro. In the same time, we measured the stress on the intervertebral disc. (2) In the base of the normal finite element model, we simulated the degenerational disc by modified the mechanical characters and height of the disc model. Then under the 45N preload the model is loaded the 2.0N moment to simulate the flexion/extension, left/right bending and rotating. We observe the ROM of FSU and the stress on the disc and compare them with the data of normal FEM. (3) By modified the material and mechanical characters of the disc(Cs/6) we simulated bone graft and fusion in the between C5 and Cs vertebral body. Under the 45N preload the model is loaded the 2.0N moment to simulate the flexion/extension, left/right bending and rotating. Then we observe the ROM of FSU(C4/s) and the stress on the C4/5 intervertabral disc and compare them with the data of normal FEM. ? In the FEM we replace the C4/5 intervertabral disc with the model of artificial cervical intervertebral disc. Under the 45N preload the model is loaded the 2.0N moment to simulate the flexion/extension, left/right bending and rotating. We observe the ROM of FSU(C4/s) and compare them with the data of normal FEM.Results (D The results of the finite element model are match to the results of the in vitro experiment of biomechanics(p<0.01). ?There are significant diffrence(p<0.01) in ROM and stress between degenerational cervical disc and normal disc. (3) After the fusion of C5/6, the ROM and stress of FSU(C4/s) is markedly increased (PO.05). (D There are no difference in ROM(flexion, left/right bending) of FSU(C4/5) between before and after the replacement of artificial cervical intervertebral disc.Conclusion ? The finite element modelof the cervical spine can simulate the characteristic of biomechanics. (2) Degeneration of cervical disc can cause the spinal instability and the spinal instability can aggravate degeneration. (D The bone graft and fusion of cervical intervertebral body can aggravate the spinal instability degeneration of disc in the adjacent FSU. ? A good artificial cervical intervertebral disc can simulate physiologic function of the normal intervertebral disc.