Background

Powered ankle-foot prostheses were developed to replicate the mechanics of the biological ankle by providing positive work during the push-off phase of gait. However, the benefits of powered prostheses on improving overall human gait efficiency (usually quantified by metabolic cost) have not been consistently shown. Here, we have focused on the mechanical work produced at the prosthetic ankle and its interaction with the amputee's movement.

Methods

Five unilateral transtibial amputees walked on a treadmill using 1) a powered ankle-foot prosthesis and 2) their daily passive device. We determined the net ankle work and ankle work loops on the prosthesis-side to quantify the efficiency of the human-prosthesis physical interaction. We further studied peak propulsion timing and the posture of the amputee's lower limb and prosthesis as indicators of the human-prosthesis coordination. Comparisons were made between the passive and powered prosthesis conditions for each participant.

Findings

The powered prosthesis did not consistently increase net ankle work compared to each participant's passive device. For participants that lacked efficiency in interacting with the powered prosthesis, we observed 1) early prosthesis-side peak propulsion timing (≥ 4% earlier) and 2) a more vertical residual shank at the time of peak propulsion (> 2° more vertical) indicating that the human's limb movement and the prosthesis control during push-off were not well coordinated.

Interpretation

Results from this preliminary study highlight the need for future work to systematically quantify the coordination between the human and powered prosthesis and understand how such coordination at the joint level influences overall gait efficiency.

中文翻译：

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人体-假肢协调：探索与动力踝足假肢协调的初步研究。

背景

电动踝足假肢的开发旨在通过在步态的推出阶段提供积极的工作来复制生物踝关节的力学。然而，动力假肢在提高整体人类步态效率（通常通过代谢成本量化）方面的好处尚未得到一致显示。在这里，我们专注于假肢踝关节产生的机械功及其与截肢者运动的相互作用。

方法

五名单侧胫骨截肢者使用 1) 电动踝足假肢和 2) 日常被动装置在跑步机上行走。我们确定了假肢侧的净脚踝功和脚踝功循环，以量化人与假肢物理交互的效率。我们进一步研究了峰值推进时间和截肢者下肢和假肢的姿势，作为人体与假肢协调的指标。对每位参与者的被动和动力假肢条件进行了比较。

发现

与每位参与者的被动装置相比，动力假肢并没有始终如一地增加净脚踝工作。对于与动力假肢互动缺乏效率的参与者，我们观察到 1) 早期假肢侧峰值推进时间（早 ≥ 4%）和 2）在峰值推进时更垂直的残余小腿（> 2° 更垂直）表明人体的肢体运动和假肢在推出过程中的控制没有很好地协调。

解释

这项初步研究的结果强调了未来工作的必要性，以系统地量化人类和动力假肢之间的协调，并了解这种关节水平的协调如何影响整体步态效率。