The Construction Of The FEM Of L2-L4 And Finite Element Analysis About Lumbar Spine Of Postmenopause Women

Objective:(1) To establish the finite element model (FEM) of L2-L4 of vertebra for further biomechanical investigation. (2) To investigate the stress and strain distributions of postmenopausal women's lumbar spine in two kinds of positions in the normal bone, the osteoporosis and the osteoporosis with fracture models. (3) To investigate the stress distribution and displacement of annulous fibrosus in normal or degenerative intervertebral disc.Materials and methods: In this study, a detailed L2-L4 three-dimensional nonlinear finite element model (FEM) of a normal woman aged 26 was established with the aid of two software MATLAB and ANSYS which can derive a nonlinear FEM from CT images. The model was validated in contrast to the date of literature. Based on the normal model, the normal bone, the osteoporosis and the osteoporosis with fracture models were built up. After loadings was employed on all models, we simulated forward and backward conditions, then recorded the Von Mises stress and the strain, the maximum stress and the ratio about trabecular bone whose strain over 5000μof intermedial vertebral body, the maximum stress and maximum displacement of annular fibrosus.Results: (1) The FEM of L2-L4 was established and validated. (2) Under forward bending condition, the ratio about trabecular bone whose strain over 5000μof intermedial vertebral body in three kinds of bone mineral density was different when the disc was normal. Under both positions, the ratio about trabecular bone whose strain over 5000μof intermedial vertebral body in each kind of bone mineral density was different between the normal and degenerative intervertebral disc. (3) The maximum stress of cortical bone of L2 and L3 in three kinds of bone mineral density was different when the intervertebral disc was normal. (4) The maximum stress and maximum displacement of annular fibrosus of normal and degenerative intervertebral disc were different in the osteoporosis, especially under forward bending condition.Conclusion: (1) The FEM of L2-L4 was built up and validated. (2) Under each bending condition, the opportunities of fracture about the three kinds of bone mineral density was different, the opportunities increased as the bone mineral density decreased. (3) Whether normal or degenerative intervertebral disc, the distribution of the Von Mises stress about the three kinds of bone mineral density was identical. (4) In degenerative intervertebral disc, the ratio of fracture of the vertebral edge increased, annular fibrosus was more easy to be destroyed under forward bending condition.