X-ray imaging and finite element analysis of the L6-S1 intervertebral disc in rats under abnormal forward-flexed posture

doi:10.12307/2026.359

Abstract

Abstract: BACKGROUND: Our group developed a rat lumbar spine model inducing L6-S1 segmental degeneration by prolonged fixation in an abnormal forward-bending posture through a specific device. However, biomechanical evaluation of this model remains lacking.
OBJECTIVE: To evaluate the biomechanical properties of L6-S1 motion segment in rats with abnormal forward bending posture through X-ray verification and finite element analysis.
METHODS: This study utilized a previously established SD rat model of abnormal forward-flexed posture. Lateral X-ray images of three healthy female SD rats were taken in both restrained (unanesthetized) and relaxed (anesthetized) states to measure the L6-S1 disc angle and analyze its changes under different postures. Micro-CT data from one healthy female SD rat were used to reconstruct a 3D L6-S1 model with Mimics, Geomagic Wrap, and SolidWorks. The model was then meshed, assigned material properties, and subjected to forward flexion loading simulation in ANSYS Workbench to calculate stress distribution in L6-S1 disc structures.
RESULTS AND CONCLUSION: (1) The mean L6-S1 intervertebral disc angle was (12.16±0.57)° in the relaxed posture and (1.26±0.26)° in the restrained posture. (2) Under a 10° forward-flexed posture, the maximum von-Mises stress in the superior endplate, inferior endplate, annulus fibrosus, and nucleus pulposus of the L6-S1 intervertebral disc was 10.398, 19.928, 6.819, and 0.104 MPa, respectively. The maximum von-Mises stress in the superior and inferior endplates was significantly higher than in the annulus fibrosus and nucleus pulposus. (3) These findings suggest that in the 10° flexion modeling posture of the L6-S1 intervertebral disc, the reduction of the L6-S1 intervertebral disc angle leads to significant changes in disc morphology and load distribution. The constructed finite element model successfully simulated the biomechanical environment of the L6-S1 intervertebral disc under abnormal forward-flexed posture in rats. The superior and inferior endplates bear higher equivalent stress in this posture, making them the structures most likely to undergo early degenerative changes.

Key words: ">rat, intervertebral disc, flexion, posture, biomechanics, finite element, X-ray, intervertebral angle

CLC Number:

He Miao, Wu Gang, Zhang Xuxing. X-ray imaging and finite element analysis of the L6-S1 intervertebral disc in rats under abnormal forward-flexed posture[J]. Chinese Journal of Tissue Engineering Research, 2026, 30(21): 5556-5564.

Figures/Tables 5

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