GEAR Laboratory, Department of Mechanical Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139.
Department of Integrated Health Sciences, University of Nevada, Las Vegas, NV 89154.
J Biomech Eng. 2023 Apr 1;145(4). doi: 10.1115/1.4056137.
Advances in understanding the effects the mechanical characteristics of prosthetic feet on user biomechanics have enabled passive prostheses to improve the walking pattern of people with lower limb amputation. However, there is no consensus on the design methodology and criteria required to maximize specific user outcomes and fully restore their mobility. The Lower Leg Trajectory Error (LLTE) framework is a novel design methodology based on the replication of lower leg dynamics. The LLTE value evaluates how closely a prosthetic foot replicates a target walking pattern. Designing a prosthesis that minimizes the LLTE value, optimizes its mechanical function to enable users to best replicate the target lower leg trajectory. Here, we conducted a systematic sensitivity investigation of LLTE-optimized prostheses. Five people with unilateral transtibial amputation walked overground at self-selected speeds using five prototype energy storage and return feet with varying LLTE values. The prototypes' LLTE values were varied by changing the stiffness of the participant's LLTE-optimized design by 60%, 80%, 120%, and 167%. Users most closely replicated the target able-bodied walking pattern with the LLTE-optimized stiffness, experimentally demonstrating that the predicted optimum was a true optimum. Additionally, the predicted LLTE values were correlated to the user's ability to replicate the target walking pattern, user preferences, and clinical outcomes including roll-over geometries, trunk sway, prosthetic energy return, and peak push-off power. This study further validates the use of the LLTE framework as a predictive and quantitative tool for designing and evaluating prosthetic feet.
对假肢脚的机械特性对用户生物力学影响的深入了解，使被动假肢能够改善下肢截肢者的行走模式。然而，对于最大化特定用户结果并充分恢复其活动能力所需的设计方法和标准，还没有达成共识。小腿轨迹误差（LLTE）框架是一种基于复制小腿动力学的新型设计方法。LLTE 值评估假肢脚复制目标行走模式的紧密程度。设计使 LLTE 值最小化的假肢，优化其机械功能，使使用者能够最佳地复制目标小腿轨迹。在这里，我们对经过 LLTE 优化的假肢进行了系统的灵敏度研究。五名单侧胫骨截肢者以自我选择的速度在地面上行走，使用了五个具有不同 LLTE 值的原型储能和返回脚。通过将参与者的经过 LLTE 优化的设计的刚度改变 60%、80%、120%和 167%，来改变原型的 LLTE 值。使用者最接近地复制了目标健全人行走模式，实验证明预测的最佳值是真实的最佳值。此外，预测的 LLTE 值与使用者复制目标行走模式的能力、使用者偏好以及包括滚过几何形状、躯干摆动、假肢能量返回和峰值推离功率在内的临床结果相关。这项研究进一步验证了使用 LLTE 框架作为设计和评估假肢脚的预测性和定量工具。
