青少年坐姿时腰部受力数值模拟

Numerical simulation on waist loads for the juvenile under sitting posture

为了定量研究青少年坐姿时腰部受力情况,根据静力学原理,结合人体测量学对青少年坐姿时腰椎各节段所承受的重力矩进行分析,探讨腰椎各节段竖脊肌的肌力大小以及腰椎各椎体所承受的剪切力和挤压力。对腰椎部位进行CT扫描,应用Mimics和Ansys软件对数据进行三维重建并分析。通过分析发现腰椎各节段承载的负荷与躯干前倾角度密切相关,在脊柱前曲逐渐增大时,上位体重对腰椎的压力在竖直方向的分量减小而在水平方向的分量增大,从而引起周围软组织水平方向负荷的增加。躯干前倾角度为30°时,各椎体最大应力自上而下依次分别为:4.01MPa、7.26 MPa、7.29 MPa、11.07 MPa、15.64 MPa,各椎间盘的最大应力自上而下依次分别为:1.3 MPa、1.81 MPa、1.83 MPa、2.19 MPa。有限元法分析结果表明:椎体是承载应力的主要结构,椎间盘起到传递载荷的作用,坐姿时椎体的前下方出现应力集中现象;在坐姿时应尽量减少脊柱的前倾角度,将脊柱的前倾角度控制在30°范围之内,以降低椎体及椎间盘所承受的负荷,从而减少腰椎及其椎间盘损伤的风险。

To establish the numerical model of lumbar and study quantitatively waist loads for the juvenile under sitting posture so as to provide a new method for adjusting sitting posture for the juvenile.Based on statics theory and anthropometry to analyze the gravity torque,erector spinae muscle strength as well as the extrusion pressure and shear stress acted on the lumbar segments for the juvenile under sitting posture,based on CT of healthy juvenile,the vertebra and intervertebral disc of lumbar are reconstructed by using softwares Mimics and ANSYS,respectively.The load acting on the lumbar segments is closely related to the spine forward tilt angle.When the tilt angle is gradually increased,the vertical component of the pressure on the lumbar segments produced by the upper body weight will reduce,but the horizontal component will increase,thereby,this will cause the load increase on the around soft tissue in the horizontal direction.When the spine forward tilt angle is 30°,the maximum stresses of vertebral bodies from up to down are respectively:4.01MPa,7.26MPa,7.29MPa,11.07MPa and 15.64MPa,the maximum equivalent stress on intervertebal discs are respectively:1.3MPa,1.81MPa,1.83MPa and 2.19MPa.The vertebra is the main structure of bearing stress,the intervertebal disc plays the role of transferring the loads,during sitting the equivalent stress concentrates on the anterior-lower location of vertebral body.To reduce the loads on the vertebral body and intervertebral disc and decrease the trauma risk of lumbar vertebra and interverteral discs,the spine forward angle should be reduced under sitting station,which should be controlled within range of 30°.