The Effects of Passive Ankle-Foot Orthotic Devices’ Stiffness – Application and Limitation of 2D Inverted Pendulum Gait Model

Abstract

This paper presents a pilot study for the development of a lumped parameter model that can facilitate the interpretation of gait data and design AFOs. A 2-D kinematic link model was constructed first and then adapted into a lumped parameter model with inverted pendulum approach. A patient with ankle disability was recruited and performed three walks with different ankle stiffness support: no AFO, medium-stiff (3.6 N·m/deg) AFOs, and stiff (4.5 N·m/deg) AFOs. An inertia measurement unit (IMU) system was used to measure the sagittal kinematics of the impaired and unimpaired limbs, and the data collected was used as inputs for the proposed gait model. Good agreement between observed and predicted swing time of the unimpaired side based on given AFO stiffness was achieved.