Torso flexion loads and the fatigue failure of human lumbosacral motion segments
Torso flexion loads and the fatigue failure of human lumbosacral motion segments
复制标题
DOI：
10.1097/01.brs.0000182086.33984.b3
复制
发表时间：
2005-10-15
期刊：
影响因子：
3
通讯作者：
Burr, D
中科院分区：
文献类型：
--
作者：
Gallagher, S;Marras, WS;Burr, D
研究设计。在三个躯干弯曲角度（0 度、22.5 度和 45 度）下估计与举起 9 公斤重物相关的脊柱负荷，并使用这些负荷对腰骶运动节段进行循环加载，直至失效或最多 10,020 个循环。 目标。模拟不同躯干屈曲姿势下重复举起中等重量时腰椎所经历的姿势和载荷，分析腰骶运动节段的疲劳失效反应。背景数据摘要。先前的腰椎运动节段疲劳失效研究并未再现职业环境中的举重任务期间不同躯干弯曲姿势中预期的脊柱姿势、负载和负载率的组合。方法。将 12 个新鲜的人腰骶棘解剖成三个运动节段（L1-L2、L3-L4 和 L5-S1）。使用部分平衡的不完整块实验设计，将每个脊柱内的运动节段随机分配给模拟的躯干弯曲角度（0 度、22.5 度或 45 度）。使用先前从肌电图辅助生物力学模型收集的数据确定每个躯干弯曲角度的脊柱负荷和负荷率。运动段蠕变加载 15 分钟，然后以 0.33 Hz 循环加载。疲劳寿命被视为失效的循环次数（蠕变载荷后位移 10 毫米）。检查样本以确定失效机制。结果。躯干弯曲程度对衰竭周期有巨大影响。经历 0 躯干屈曲条件的运动节段平均持续 8,253 个周期（+/- 2,895），而 22.5 度躯干屈曲角度平均 3,257（+/-4,443）个周期失效，而 45 度躯干屈曲角度的运动节段平均仅持续 263 个周期（+/-646）。差异显着，P < 0.0001，躯干屈曲占失效周期总方差的 50%。结论。当躯干在职业举重任务中完全弯曲时，脊柱组织会迅速发生疲劳衰竭；然而，在中立姿势下可以容忍数千次循环。未来的举重建议应该对躯干屈曲疲劳失效的快速发展敏感。
Study Design. Spine loads associated with lifting a 9-kg weight were estimated at three torso flexion angles (0 degrees, 22.5 degrees, and 45 degrees), and lumbosacral motion segments were cyclically loaded using these loads until failure or to a maximum of 10,020 cycles.Objectives. To simulate the postures and loads experienced by the lumbar spine during repetitive lifting of moderate weights in different torso flexion postures, and to analyze the fatigue failure response of lumbosacral motion segments.Summary of Background Data. Previous fatigue failure studies of lumbar motion segments have not reproduced the combination of spinal postures, loads, and load rates anticipated in different torso flexion postures during lifting tasks characteristic of those in occupational settings.Methods. Twelve fresh human lumbosacral spines were dissected into three motion segments each (L1-L2, L3-L4, and L5-S1). Motion segments within each spine were randomly assigned to a simulated torso flexion angle (0 degrees, 22.5 degrees, or 45 degrees) using a partially balanced incomplete block experimental design. Spinal load and load rate were determined for each torso flexion angle using previously collected data from an EMG-assisted biomechanical model. Motion segments were creep loaded for 15 minutes, then cyclically loaded at 0.33 Hz. Fatigue life was taken as the number of cycles to failure (10 mm displacement after creep loading). Specimens were inspected to determine failure mechanisms.Results. The degree of torso flexion had a dramatic impact on cycles to failure. Motion segments experiencing the 0 torso flexion condition averaged 8,253 cycles to failure (+/- 2,895), while the 22.5 degrees torso flexion angle averaged 3,257 (+/-4,443) cycles to failure, and motion segments at the 45 torso flexion angle lasted only 263 cycles (+/-646), on average. The difference was significant at P < 0.0001, and torso flexion accounted for 50% of the total variance in cycles to failure.Conclusions. Fatigue failure of spinal tissues can occur rapidly when the torso is fully flexed during occupational lifting tasks; however, many thousands of cycles can be tolerated in a neutral posture. Future lifting recommendations should be sensitive to rapid development of fatigue failure in torso flexion.