Alterations in Amputee Gait Mechanics Produced by Varied Stiffness and Damping in a Shock Absorbing Prosthetic Pylon

Open Access
Author:
Ligouri, Anthony Thomas
Graduate Program:
Mechanical Engineering
Degree:
Master of Science
Document Type:
Master Thesis
Date of Defense:
July 13, 2015
Committee Members:
  • Stephen Jacob Piazza, Thesis Advisor
Keywords:
  • prosthetics
  • energy harvesting
  • amputee
  • gait
  • energy scavenging
Abstract:
Advanced electrically powered prostheses have become increasingly common in recent years for use by amputees. Their power requirements are of considerable concern due to their need for frequent charging and potential to cause problems if they lose power. Energy harvesting from human locomotion has been studied by many researchers as a potential means to meet these power requirements. The main purpose of this thesis is to investigate the effects of varied stiffness and damping of a shock absorbing prosthetic pylon on unilateral, transtibial amputee gait in an attempt to characterize the effects of a real energy harvesting prosthetic pylon. We investigated the variations in intact side ankle moment and power and intact side hip moment and power of five unilateral, transtibial amputees walking with a shock absorbing pylon across five different stiffness and damping combinations. We also conducted a computational modeling study in which we simulated a unilateral, transtibial amputee walking with a shock absorbing pylon with 30 different combinations of stiffness and damping and investigated the differences in intact side ankle moment and power, knee moment and power, hip moment and power, and center of mass acceleration. Variation of both stiffness and damping had significant effects on intact side joint kinetics, but not all subjects reacted in the same way to increasing stiffness and damping. In general, a more compliant pylon allowed amputees to walk with reduced joint moments and powers. Modeling results suggested that some combinations of stiffness and damping can minimize user effort while still effectively harvesting energy. This thesis is the first study to investigate the effects of a shock absorbing prosthetic pylon containing both a spring and damper on amputee gait.