Design of modular self contained knee and ankle prostheses

Abstract

Losing a lower limb and specifically the power that it generates, has a major impact on ambulation including having to expend more metabolic energy and exert more hip power and torque on the affected side. There are currently a small number of commercially available powered prostheses but they are not capable of providing the full range of motion and power of the lost limb. Additionally there are no prostheses which have both a powered knee and ankle joint. It is the hypothesis of this work that lower limb prosthetic devices can be designed which provide biomechanically normal levels of torque, speed, and range of motion in self-contained, reliable, quiet, and anatomical packages. Described herein is the mechanical design, development and testing of several such devices. Initial work focused on the development of several key components including a ground contact sensing load cell, a biasing spring foot, and a robust and compact transmission design. Subsequent work incorporated these components into a transfemoral prosthesis with powered knee and ankle joints. In addition, a transtibial version was fabricated with a powered ankle joint. Both of these designs conform closely to the anatomical envelope of an average sized male limb. Experiments with amputee subjects validate the design through the demonstration of kinematics and kinetics that closely match those of the lost limb.