Guzik D C, Keller T S, Szpalski M, Park J H, Spengler D M
Department of Mechanical Engineering, University of Vermont, Burlington, USA.
Spine (Phila Pa 1976). 1996 Feb 15;21(4):427-33. doi: 10.1097/00007632-199602150-00005.
Task-specific and subject-specific lumbar trunk muscle function, muscle geometry, and vertebral density data were collected from 16 men. A biomechanical model was used to determine muscle strength and the compressive forces acting on the lumbar spine.
To develop an anatomic biomechanical model of the low back that could be used to derive task-specific muscle function parameters and to predict compressive forces acting on the low back. Several model-specific constraints were examined, including the notion of bilateral trunk muscle anatomic symmetry, the influence of muscle lines of action, and the use of density-derived vertebral strength for model validation.
Clinical and basic science investigators are currently using a battery of diverse biomechanical techniques to evaluate trunk muscle strength. Noteworthy is the large variability in muscle function parameters reported for different subjects and for different tasks. This information is used to calculate forces and moments acting on the low back, but limited data exist concerning the assessment of subject-specific, multiaxis, isometric trunk muscle functions.
A trunk dynamometer was used to measure maximum upright, isometric trunk moments in the sagittal (extension, flexion) and coronal (lateral flexion) planes. Task- and subject-specific trunk muscle strength or "gain" was determined from the measured trunk moments and magnetic resonance image-based muscle cross-sectional geometry. Model-predicted compressive forces obtained using muscle force and body force equilibrium equations were compared with density-derived estimates of compressive strength.
Individual task-specific muscle gain values differed significantly between subjects and between each of the tasks they performed (extension > flexion > lateral flexion). Significant differences were found between left side and right side muscle areas, and the lines of action of the muscles deviated significantly from the vertical plane. Model-predicted lumbar compressive forces were 38% (lateral flexion) to 73% (extension) lower that the L3 vertebral compressive strength estimated from vertebral density.
The present study suggests that biomechanical models of the low back should be based on task-specific and subject-specific muscle function and precise geometry. Vertebral strength estimates based upon vertebral density appear to be useful for validation of model force predictions.
收集了16名男性特定任务和特定个体的腰椎躯干肌肉功能、肌肉几何形状及椎体密度数据。使用生物力学模型来确定肌肉力量以及作用于腰椎的压缩力。
建立一个下背部的解剖生物力学模型，该模型可用于推导特定任务的肌肉功能参数，并预测作用于下背部的压缩力。研究了几个特定于模型的约束条件，包括双侧躯干肌肉解剖对称性的概念、肌肉作用线的影响以及使用基于密度的椎体强度进行模型验证。
临床和基础科学研究人员目前正在使用一系列不同的生物力学技术来评估躯干肌肉力量。值得注意的是，针对不同受试者和不同任务报告的肌肉功能参数存在很大差异。这些信息用于计算作用于下背部的力和力矩，但关于特定个体、多轴、等长躯干肌肉功能评估的数据有限。
使用躯干测力计测量矢状面（伸展、屈曲）和冠状面（侧屈）内最大直立等长躯干力矩。根据测量的躯干力矩和基于磁共振图像的肌肉横截面几何形状确定特定任务和特定个体的躯干肌肉力量或“增益”。将使用肌肉力和体力平衡方程获得的模型预测压缩力与基于密度的压缩强度估计值进行比较。
个体特定任务的肌肉增益值在受试者之间以及他们执行的每个任务之间存在显著差异（伸展>屈曲>侧屈）。发现左侧和右侧肌肉面积之间存在显著差异，并且肌肉的作用线明显偏离垂直平面。模型预测的腰椎压缩力比根据椎体密度估计的L3椎体压缩强度低38%（侧屈）至73%（伸展）。
本研究表明，下背部的生物力学模型应基于特定任务和特定个体的肌肉功能及精确的几何形状。基于椎体密度的椎体强度估计似乎有助于验证模型力预测。
