Characterizing intersection variability of butterfly diagram in post-stroke gait using Kernel Density Estimation
Characterizing intersection variability of butterfly diagram in post-stroke gait using Kernel Density Estimation
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DOI：
10.1016/j.gaitpost.2019.12.005
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发表时间：
2020-02-01
期刊：
影响因子：
2.4
通讯作者：
Liang, Jing Nong
中科院分区：
文献类型：
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作者：
Lee, Yun-Ju;Liang, Jing Nong
背景：跑步机行走时的压力中心 (COP) 轨迹通常使用蝴蝶图来描述神经完好和受损个体的步态特征。然而，由于显示的信息量很大，蝴蝶图并不是可视化运动变异性的有效解决方案。目的：本研究的目的是通过在蝴蝶图的交点上应用核密度估计（KDE）来评估中风后运动变异性，并将 KDE 导出的指标与步态对称性和变异性的传统指标进行比较。方法：确定蝴蝶图的双侧脚趾离地（TO）和初始接触（IC）点以计算 COP 对称性索引和双边 TO-IC 的交集。随后，通过核密度估计，使用行走窗口期间的交叉点来评估其密度和变异性。比较各组之间步宽和步长的标准差。结果：使用 KDE 曲面图，我们观察到中风后个体的 4 种特征不同的模式，这些模式与使用步行速度和下肢 Fugl-Meyer 评分量化的功能状态相关。然而，使用步宽和长度的标准偏差量化的运动变异性在各组之间没有差异。 意义和新颖性：本文提出了一种新方法，与步态对称性和变异性的传统指标相比，使用 KDE 分析作为一种更好、更灵敏的方法来表征中风后偏瘫个体的运动 COP 变异性。
Background: Center of pressure (COP) trajectory during treadmill walking have been commonly presented using the butterfly diagram to describe gait characteristics in neurologically intact and impaired individuals. However, due to the large amount of displayed information, the butterfly diagram is not an efficient solution to visualize locomotor variability.Purpose: The purpose of this study was to evaluate post-stroke locomotor variability by applying Kernel density estimation (KDE) on the intersections of the butterfly diagram, and to compare KDE derived metrics with conventional metrics of gait symmetry and variability.Methods: Bilateral toe-off (TO) and initial contact (IC) points of the butterfly diagram were determined to calculate the COP symmetry index and the intersections of bilateral TO-IC. Subsequently, the intersections during the walking window were used to evaluate its density and variability by Kernel density estimation. Standard deviations of step width and step length were compared between groups.Results: Using the KDE surface plots we observed 4 characteristically different patterns with individuals poststroke, which were associated with functional status quantified using walking speed and lower extremity Fugl-Meyer scores. However, locomotor variability quantified using standard deviations of step width and lengths did not differ between groups.Significance & Novelty: This paper presents a novel approach of using KDE analysis as a better and more sensitive method to characterize locomotor COP variability in individuals with post-stroke hemiparesis, compared to conventional metrics of gait symmetry and variability.