Model establishment and stress analysis on the different types of sagittal lumbar-pelvic alignment

English Keywords:The sagittal lumbar-pelvic alignment  Finite element analysis  Biomechanics

English Abstract:

  【Abstract】 Objectives: To establish 4 cases of lumbar finite element model, according to the classification of sagittal lumbar-pelvic alignment, and to compare the stress distribution in the intervertebral disc and the vertebral arch isthmus. Methods: On the basis of the sagittal lumbar-pelvic alignment, 4 young healthy volunteers were selected, 1 volunteer for each type (type Ⅰ, female, 20 years old; type Ⅱ, male, 21 years old; type Ⅲ, male, 26 years old; type Ⅳ, female, 19 years old). 4 volunteers underwent lumbar CT examination, and were built L1-L5 lumbar finite element models of 4 cases by using Mimics, Geomagic, Hypermesh, ABAQUS. After applying the 400N vertical compression load and the torque load of 10N·m along the X, Y and Z axes, the average stiffness of the models was calculated under the conditions of flexion, extension, lateral bending and axial rotation, and the validity of models was verified. Under the condition of only applying 400N vertical compression load, the stress distributions of the annulus fibrosus and the vertebral arch isthmus were analyzed. Results: Under the conditions of flexion, extension, lateral bending and axial rotation, the average stiffness of 4 cases was similar to that of previous vitro experiment. After applying 400N vertical compression load, the stress of annulus fibrosus from L1/2 to L4/5 increased gradually, and the stress was mostly concentrated in the posterior part of annulus fibrosus. In type Ⅰ and Ⅱ, the stress of isthmus was mainly focused on L4, however, in type Ⅲ and Ⅳ, the stress of isthmus was mainly focused on L3. From type Ⅰ to type Ⅳ, the mean stress of the posterior part of annulus fibrosus from L4/5 to L1/2 decreased gradually(203.69%, 197.58%，167.74%, 139.85%). However, the mean stress of bilateral vertebral arch isthmus from L5 to L1 increased gradually(204.38%, 212.59%, 271.43%, 292.98%). Conclusions: In the different types of sagittal lumbar-pelvic alignment, there are different types of stress distribution of the annulus fibrosus and the vertebral arch isthmus.