Eskandari A H, Arjmand N, Shirazi-Adl A, Farahmand F
Department of Mechanical Engineering, Sharif University of Technology, Tehran, Iran.
Department of Mechanical Engineering, Sharif University of Technology, Tehran, Iran.
J Biomech. 2017 May 24;57:18-26. doi: 10.1016/j.jbiomech.2017.03.011. Epub 2017 Mar 21.
An essential input to the musculoskeletal (MS) trunk models that estimate muscle and spine forces is kinematics of the thorax, pelvis, and lumbar vertebrae. While thorax and pelvis kinematics are usually measured via skin motion capture devices (with inherent errors on the proper identification of the underlying bony landmarks and the relative skin-sensor-bone movements), those of the intervening lumbar vertebrae are commonly approximated at fixed proportions based on the thorax-pelvis kinematics. This study proposes an image-based kinematics measurement approach to drive subject-specific (musculature, geometry, mass, and center of masses) MS models. Kinematics of the thorax, pelvis, and individual lumbar vertebrae as well as disc inclinations, gravity loading, and musculature were all measured via different imaging techniques. The model estimated muscle and lumbar forces in various upright and flexed postures in which kinematics were obtained using upright fluoroscopy via 2D/3D image registration. Predictions of this novel image-kinematics-driven model (Img-KD) were compared with those of the traditional kinematics-driven (T-KD) model in which individual lumbar vertebral rotations were assumed based on thorax-pelvis orientations. Results indicated that while differences between Img-KD and T-KD models remained small for the force in the global muscles (attached to the thoracic cage) (<15%), L4-S1 compression (<15%), and shear (<20%) forces in average for all the simulated tasks, they were relatively larger for the force in the local muscles (attached to the lumbar vertebrae). Assuming that the skin-based measurements of thorax and pelvis kinematics are accurate enough, the T-KD model predictions of spinal forces remain reliable.
用于估计肌肉和脊柱受力的肌肉骨骼（MS）躯干模型的一个重要输入是胸部、骨盆和腰椎的运动学数据。虽然胸部和骨盆的运动学通常通过皮肤运动捕捉设备进行测量（在正确识别潜在骨标志以及皮肤 - 传感器 - 骨的相对运动方面存在固有误差），但中间腰椎的运动学通常基于胸部 - 骨盆运动学按固定比例近似估算。本研究提出了一种基于图像的运动学测量方法，以驱动特定个体的（肌肉组织、几何形状、质量和质心）MS模型。胸部、骨盆和各个腰椎的运动学以及椎间盘倾斜度、重力负荷和肌肉组织均通过不同的成像技术进行测量。该模型估计了各种直立和弯曲姿势下的肌肉和腰部受力情况，其中运动学数据是通过二维/三维图像配准的直立荧光透视法获得的。将这种新型图像运动学驱动模型（Img - KD）的预测结果与传统运动学驱动（T - KD）模型的预测结果进行了比较，在传统模型中，个体腰椎旋转是基于胸部 - 骨盆方向假设的。结果表明，虽然在所有模拟任务中，Img - KD模型和T - KD模型在全局肌肉（附着于胸廓）受力方面的差异较小（<15%），L4 - S1压缩力方面差异较小（<15%），剪切力方面平均差异较小（<20%），但在局部肌肉（附着于腰椎）受力方面差异相对较大。假设基于皮肤的胸部和骨盆运动学测量足够准确，T - KD模型对脊柱受力的预测仍然可靠。
