2022, Vol. 26 ›› Issue (33): 5249-5253

Mechanics analysis of sacral lumbarization based on finite element method

Li Jian1, 2, Guan Tianmin1, Zhu Ye1   

Abstract: BACKGROUND: Sacral lumbarization will lead to changes in spinal segments, so that mechanical structure of spine is going to change, more likely to cause spinal lesions.
OBJECTIVE: To analyze statics difference between the sacral lumbarization model and the normal model.
METHODS: According to principle of reverse engineering and data based on CT, lumbosacral geometric models were set up. The sacral lumbarization model was in the experimental group and normal model was in the control group. Gradient was attributed to the material based on gray value of CT data and ligament model was set up. A concentrated force of 200 N was applied to the L4 vertebral body surface to simulate gravity. Simultaneously, a moment of 2 N·m was applied to the positive and negative directions of the X axis, Y axis and Z axis to simulate six conditions of sports: anteflexion and posterior extension, right and left lateral flexion and rotation. The stress distribution of the model, the deflection angle of the vertebral body, and the stress distribution between the intervertebral disc L5 and the sacrum were analyzed.
RESULTS AND CONCLUSION: (1) Under six conditions, the stress concentration of sacral lumbarization model obviously occurred at the contact of the articular processes of S1 and S2 in the experimental group. Deflection angle was significantly larger in the experimental group than that in the control group. (2) From the stress nephogram of intervertebral disc distribution, the stress distribution area of experimental group and control group was close, which was fit for the stress characteristics of the spine. However, the stress of intervertebral disc in the experimental group was significantly higher than that in the control group. The max value of 2.480 MPa appeared in the experimental group under the anteflexion condition. The max intervertebral disc stress difference value between experimental group and control group was 1.722 5 MPa. (3) To sum up, the overall structure of sacral lumbarization is more unstable. Especially, the stress concentration is more obvious at the junction of transitional vertebra and sacral vertebra, thereby affects the stability of the whole spinal force line, and then leads to the occurrence of spinal diseases.
Key words: sacral lumbarization, lumbar homeostasis, gradient assignment, finite element, CT images, reverse engineering, biomechanics