Date of Award

Spring 1-1-2017

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Integrative Physiology

First Advisor

Alena M. Grabowski

Second Advisor

Alaa A. Ahmed

Third Advisor

Rodger Kram

Fourth Advisor

William Byrnes

Fifth Advisor

Justus D. Ortega

Abstract

People with a transtibial (below-knee) amputation walking on level ground with a passive-elastic prosthesis typically experience a 10-30% greater metabolic demand than non-amputees walking at the same speed. Battery-powered ankle-foot prostheses that provide push-off power to the user have been developed that normalize the metabolic demand and biomechanics for people with a leg amputation walking on level ground. Because ramps and slopes are encountered regularly, understanding how passive and powered prostheses affect walking energetics and biomechanics for individuals with a leg amputation on a variety of slopes is critical to designing robust ankle-foot prostheses. In this dissertation, I first sought to understand the role of the biological ankle during sloped walking at various speeds. To do this, I documented the correlation between metabolic power and individual leg mechanical power at slopes of 0°, ±3°, ±6°, and ±9° and walking speeds of 1.00, 1.25, and 1.50 m/s. Then, I determined the contribution of the ankle joint to individual leg positive and negative work. Next, I recruited 10 people with a unilateral transtibial amputation to walk 1.25 m/s on slopes of 0°, ±3°, ±6°, and ±9° with passive-elastic and powered ankle-foot prostheses. I collected metabolic energy expenditure, kinetic, and kinematic data. I tuned the powered prosthesis such that prosthetic ankle range of motion, peak moment, peak power, and net work matched biological ankle (or intact ankle of the subject) values at each slope. Use of the powered prosthesis significantly reduced net metabolic power required to walk up a +3° and +6° slope by 5% compared to a passive-elastic prosthesis. Using the powered prosthesis did not significantly alter affected or unaffected individual leg step-to-step transition, hip, or knee work compared to use of a passive-elastic prosthesis. However, prosthetic ankle positive work increased at all uphill slopes and prosthetic ankle net work was more positive at all slopes with use of the powered prosthesis compared to use of a passive-elastic prosthesis. My results indicate that use of powered ankle-foot prostheses can improve walking energetics and biomechanics at uphill slopes and thus quality of life for people with a leg amputation.

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