Effects of Dynamic Alignment on the Transtibial Prosthetic Gait in the Sagittal Plane of a Kinematic Model Using OpenSim

Abstract

A sensitivity analysis of the kinematics of the transtibial amputee gait has been performed in the sagittal plane in relation to the dynamic alignment (position of the prosthesis components): flexion/extension and abduction/adduction of the socket, as well as plantar flexion/dorsiflexion and eversion/inversion of the prosthetic foot. The analysis has led to the determination of the effects on the flexion and extension in the sagittal planes of the hips, knees, and ankles of the amputated leg and the non-amputated leg. The estimation has been performed for all gait phases through a model developed in OpenSim® and Matlab®, by using the measurements of a patient with Technaid® inertial sensors and by varying the socket position in the sagittal and frontal planes between 2, 6, and 10 degrees. These measurements have been processed in Matlab® in order to deliver a motion vector. A script has been developed in order to generate the modified structural model of OpenSim® based on the static position of the vector in each case. Once the model has been obtained, the inverse kinematics of the hip, knee, and ankle have been calculated. By considering that it is not possible to perform variations on the prosthetic foot without compromising the stability of the user while taking measurements, a model variant in which a neural network is trained to estimate the kinematics of the hip, knee, and ankle has been developed. Regarding the prosthetic foot, the changes derived from modifications in dorsiflexion, plantar flexion, eversion, and inversion positions significantly alter the kinematics of the hip and knee.