School of Mechanical Engineering, Shanghai Jiao Tong University, Shanghai, China.
Department of Movement Sciences, KU Leuven, Leuven, Belgium.
Ann Biomed Eng. 2021 Sep;49(9):2311-2322. doi: 10.1007/s10439-021-02774-3. Epub 2021 Apr 13.
This study aims to propose a new optimization framework for solving spine kinematics based on skin-mounted markers and estimate subject-specific mechanical properties of the intervertebral joints. The approach enforces dynamic consistency in the entire skeletal system over the entire time-trajectory while personalizing spinal stiffness. 3D reflective markers mounted on ten vertebrae during spine motions were measured in ten healthy volunteers. Biplanar X-rays were taken during neutral stance of the subjects wearing the markers. Calculated spine kinematics were compared to those calculated using inverse kinematics (IK) and IK with imposed generic kinematic constraints. Calculated spine kinematics compared well with standing X-rays, with average root mean square differences of the vertebral body center positions below 10.1 mm and below [Formula: see text] for joint orientation angles. For flexion/extension and lateral bending, the lumbar rotation distribution patterns, as well as the ranges of rotations matched in vivo literature data. The approach outperforms state-of-art IK and IK with constraints methods. Calculated ratios reflect reduced spinal stiffness in low-resistance zone and increased stiffness in high-resistance zone. The patterns of calibrated stiffness were consistent with previously reported experimentally determined patterns. This approach will further our insight into spinal mechanics by increasing the physiological representativeness of spinal motion simulations.
本研究旨在提出一种新的基于皮肤贴标记的脊柱运动学优化框架，用于估计个体关节的机械特性。该方法在整个时间轨迹上强制整个骨骼系统的动态一致性，同时个性化脊柱刚度。在 10 名健康志愿者进行脊柱运动时，在 10 个椎体上安装了 3D 反光标记。在受试者佩戴标记物的中立站位拍摄双平面 X 光片。计算出的脊柱运动学与使用反向运动学（IK）和施加通用运动学约束的 IK 计算出的运动学进行了比较。计算出的脊柱运动学与站立 X 光片相比吻合良好，椎体中心位置的平均均方根差低于 10.1mm，关节方位角的平均均方根差低于 [公式：见文本]。对于屈伸和侧屈，腰椎旋转分布模式以及旋转范围与体内文献数据相匹配。该方法优于最先进的 IK 和带约束的 IK 方法。计算出的比值反映了低阻力区的脊柱刚度降低和高阻力区的刚度增加。校准的刚度模式与之前报道的实验确定的模式一致。该方法将通过增加脊柱运动模拟的生理代表性，进一步深入了解脊柱力学。
