Aiyangar Ameet, Zheng Liying, Anderst William, Zhang Xudong
Empa, Swiss Federal Laboratories for Materials Science and Technology, Mechanical Systems Engineering, Ueberlandstrasse 129, 8600 Duebendorf, Switzerland.
Department of Mechanical Engineering and Materials Science, University of Pittsburgh, Pittsburgh, PA 15203, USA; Health Effects Lab Division, National Institute for Occupational Safety and Health, Morgantown, West Virginia, 26505, USA.
J Biomech. 2017 Feb 8;52:113-121. doi: 10.1016/j.jbiomech.2016.12.021. Epub 2016 Dec 29.
The study aimed to map instantaneous centers of rotation (ICRs) of lumbar motion segments during a functional lifting task and examine differences across segments and variations caused by magnitude of weight lifted. Eleven healthy participants lifted loads of three different magnitudes (4.5, 9, and 13.5kg) from a trunk-flexed (~75°) to an upright position, while being imaged by a dynamic stereo X-ray (DSX) system. Tracked lumbar vertebral (L2-S1) motion data were processed into highly accurate 6DOF intervertebral (L2L3, L3L4, L4L5, L5S1) kinematics. ICRs were computed using the finite helical axis method. Effects of segment level and load magnitude on the anterior-posterior (AP) and superior-inferior (SI) ICR migration ranges were assessed with a mixed-effects model. Further, ICRs were averaged to a single center of rotation (COR) to assess segment-specific differences in COR AP- and SI-coordinates. The AP range was found to be significantly larger for L2L3 compared to L3L4 (p=0.02), L4L5 and L5S1 (p<0.001). Average ICR SI location was relatively higher - near the superior endplate of the inferior vertebra - for L4L5 and L5SI compared to L2L3 and L3L4 (p≤0.001) - located between the mid-transverse plane and superior endplate of the inferior vertebra - but differences were not significant amongst themselves (p>0.9). Load magnitude had a significant effect only on the SI component of ICR migration range (13.5kg>9kg and 4.5kg; p=0.049 and 0.017 respectively). The reported segment-specific ICR data exemplify improved input parameters for lumbar spine biomechanical models and design of disc replacements, and base-line references for potential diagnostic applications.
该研究旨在绘制功能性提举任务期间腰椎运动节段的瞬时旋转中心（ICR），并检查各节段之间的差异以及由提举重量大小引起的变化。11名健康参与者从躯干屈曲（约75°）到直立位置提举三种不同大小（4.5、9和13.5千克）的负荷，同时由动态立体X射线（DSX）系统进行成像。跟踪的腰椎（L2-S1）运动数据被处理成高精度的6自由度椎间（L2L3、L3L4、L4L5、L5S1）运动学数据。使用有限螺旋轴方法计算ICR。采用混合效应模型评估节段水平和负荷大小对前后（AP）和上下（SI）ICR迁移范围的影响。此外，将ICR平均为单个旋转中心（COR），以评估COR的AP和SI坐标中的节段特异性差异。发现L2L3的AP范围比L3L4（p=0.02）、L4L5和L5S1（p<0.001）显著更大。与L2L3和L3L4相比，L4L5和L5SI的平均ICR SI位置相对较高——靠近下位椎体的上终板（p≤0.001）——位于下位椎体的中横平面和上终板之间——但它们之间的差异不显著（p>0.9）。负荷大小仅对ICR迁移范围的SI分量有显著影响（13.5千克>9千克和4.5千克；分别为p=0.049和0.017）。所报告的节段特异性ICR数据为例证，可为腰椎生物力学模型和椎间盘置换设计提供改进的输入参数，以及为潜在诊断应用提供基线参考。
