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

• The L6-S1 disc angle significantly decreased from (12.16±0.57)° in relaxed posture to (1.26±0.26)° in restrained posture, confirming morphological changes under abnormal forward flexion. • Finite element analysis revealed that under 10° forward flexion, the lower endplate experienced the highest von Mises stress (19.928 MPa), followed by the upper endplate (10.398 MPa), annulus fibrosus (6.819 MPa), and nucleus pulposus (0.104 MPa). • Endplates bore significantly greater stress than other disc structures, suggesting they may be the first to undergo degenerative changes in this model. • The study provides biomechanical validation for the novel rat model of abnormal forward-flexed posture, supporting its use in disc degeneration research.