Department of Mechanical Engineering, University of Pittsburgh, Pittsburgh, PA, USA.
Mechanical Systems Engineering, EMPA-Swiss Federal Laboratories for Materials Science and Technology, Duebendorf, Switzerland; Department of Orthopaedic Surgery, University of Pittsburgh, Pittsburgh, PA, USA.
J Biomech. 2020 Mar 26;102:109659. doi: 10.1016/j.jbiomech.2020.109659. Epub 2020 Jan 31.
The study investigated the potential for obtaining more accurate spine joint reaction force (JRF) estimates from musculoskeletal models by incorporating dynamic stereo X-ray imaging (DSX)-based in vivo lumbar vertebral rotational and translational kinematics compared to generic, rhythm (RHY)-based kinematics, while also observing the influence of accompanying inputs: intervertebral segment stiffness and neutral state. A full-body OpenSim® musculoskeletal model, constructed by combining existing lower- and upper-body models, was driven based on one volunteer's (female; age 25; 60.8 kg; 176 cm) anthropometrics and kinematics from a series of upright standing and straight-legged dynamic lifting tasks. The lumbar spine portion was modified in a step-wise manner to observe effects of: (1) RHY vs. DSX lumbar kinematics; (2) No disc (bushing) stiffness (NBS); generic, linear bushing stiffness (LBS); subject-specific nonlinear bushing stiffness (NLBS); (3) Upright standing (UP) vs. Supine (SUP) neutral state; (4) Weight lifted: 4.5 kg vs. 13.6 kg. L4L5 JRF from 24 model variations based on combinations of aforementioned parameters were compared. Rhythm-based kinematics without translational components tends to over-predict JRF (31% and 39% for compression and shear, respectively) compared to DSX-based kinematics. Additionally, differences due to accompanying passive stiffness and neutral state choice combinations were even larger (>50%), indicating heightened demand on the quality of these accompanying inputs. The study not only highlights model sensitivity to choices made regarding the three primary inputs-kinematics, passive stiffness and neutral state- separately, but also how interactions between these choices can result in significant variability in joint loading estimates.
本研究通过将基于动态立体 X 射线成像（DSX）的体内腰椎旋转和平移运动学与通用的节律（RHY）运动学进行比较，研究了通过肌骨模型获得更准确的脊柱关节反作用力（JRF）估计的可能性，同时还观察了伴随输入的影响：椎间节段刚度和中性状态。一个完整的 OpenSim®肌骨模型，通过结合现有的下半身和上半身模型构建，根据一名志愿者（女性；年龄 25 岁；60.8kg；176cm）的人体测量学和一系列直立站立和直腿动态举重任务的运动学进行驱动。腰椎部分以逐步的方式进行修改，以观察以下因素的影响：（1）RHY 与 DSX 腰椎运动学；（2）无椎间盘（衬套）刚度（NBS）；通用线性衬套刚度（LBS）；个体非线性衬套刚度（NLBS）；（3）直立站立（UP）与仰卧（SUP）中性状态；（4）提升重量：4.5kg 与 13.6kg。对基于上述参数组合的 24 种模型变化的 L4L5 JRF 进行了比较。与基于 DSX 的运动学相比，没有平移分量的节律运动学往往会过高预测 JRF（压缩和剪切分别为 31%和 39%）。此外，由于伴随的被动刚度和中性状态选择组合的差异甚至更大（>50%），这表明这些伴随输入的质量要求更高。该研究不仅强调了模型对三个主要输入（运动学、被动刚度和中性状态）分别做出选择的敏感性，还强调了这些选择之间的相互作用如何导致关节载荷估计的显著变化。
