Abstract：To study the effect of segmental curvature on the stress evolution of lumbar intervertebral disc when the lumbar motion segment is subjected to long-term axial vibration. Based on the CT scan data of human lumbar spine L4～5 segment, the finite element model of human lumbar spine L4～5 segment was constructed. Poroelastic property was assigned to the intervertebral disc and the finite element model was validated. Based on this finite element model, processes of L4～5 segment subjected to a 1000-s axial vibration with different segmental curvatures (neutral posture, 2° of extension, 2° of flexion) were simulated, and the stress evolution of the intervertebral disc in those cases were obtained. With each segmental curvature, the peak axial stress of the annulus fibrosus of the intervertebral disc existed in its posterolateral part. With each segmental curvature, the peak axial stress of the annulus fibrosus increased nonlinearly and the growth rate was decreased. In all cases, the peak axial stress of the annulus fibrosus was inclined to an equilibrium state at 1000 s. At 1000 s, the peak axial stress of the annulus fibrosus in the case with the L4～5 segment in 2° of extension was 39% greater than that in the case with the L4～5 segment in neutral posture and 109% greater than that in the case with the L4～5 segment in 2° of flexion. With each curvature, the axial stress of the nucleus pulposus also increased nonlinearly and the growth rate was decreased. At 1000s, the axial stress of the nucleus pulposus in the case with the L4～5 segment in 2° of extension was slightly less than those in the other two cases. The intervertebral disc was damaged most severely when the L4～5 segment was loaded in 2° of extension, while it suffered the slightest damage when the L4～5 segment was loaded in 2° of flexion. When exposed to the whole body vibration for a long time, an extended posture of lumbar spine should be avoided, and a slight flexed posture of lumbar spine can protect the intervertebral disc.
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