轴向振动时节段曲度对腰椎间盘应力演化的影响

Effect of Segmental Curvature on Stress Evolution of Lumbar Intervertebral Disc under Axial Vibration

研究人体腰椎运动节段承受长期轴向振动载荷时节段曲度对腰椎间盘应力演化的影响。基于人体腰椎L4~5节段CT扫描数据,建立人体腰椎L4~5节段的有限元模型。对腰椎间盘赋予多孔材料属性,并验证有限元模型的有效性。基于有限元模型,模拟L4~5节段以3种不同节段曲度(中立位、伸展2°、弯曲2°)承受时长为1000 s的轴向振动的过程,得到这3种节段曲度下腰椎间盘的应力演化情况。各个曲度下腰椎间盘纤维环部分的峰值轴向应力均出现在其后外侧。在受载过程中,各个曲度下纤维环峰值轴向应力均呈非线性增大,且增速不断减小,至1000 s时已趋于稳定。1000 s时,伸展2°下纤维环峰值轴向应力比中立位下大39%,比弯曲2°下大109%。在受载过程中,各个曲度下髓核轴向应力亦呈非线性增长,增速不断减小。1000 s时,伸展2°下髓核的轴向应力略小于其他两种情形。当L4~5节段以伸展2°的状态受载时,腰椎间盘受到的损伤最为严重;而当其以弯曲2°的状态受载时,腰椎间盘受到的损伤最小。当长时间处于全身振动条件下时,应尽量避免使腰椎处于向后伸展的姿态,而腰椎的小幅前屈可以保护腰椎间盘。

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 1000 s,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.