Comparing the Biomechanics of Powered and Passive Microprocessor Knees During Community Ambulation Tasks
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Kestur, Sujay
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Abstract
Many individuals undergo lower limb amputations as a result of various conditions such as diabetes, vascular diseases, cancer and trauma. The use of a lower limb prostheses is one of the most common solutions to return the ability to complete locomotion tasks of daily living to this population. As the number of amputees is predicted to grow, advances in prosthetic technology have been made to improve patient mobility and quality of life. One of the most significant of these developments has been the introduction of the Microprocessor Prosthetic Knee (MPK). This type of prosthesis is designed to better mimic the natural movement of the knee joint and improve stability, mobility and safety during locomotion.
However, there is a lack of consensus over how different types of MPKs affect performance in different ambulation modes. In this study, we investigated the biomechanical differences between how individuals with transfemoral amputation performed ramp and stair maneuvers wearing one of three commercial MPKs: the Ossur Power Knee, the Ossur Rheo Knee and the Ottobock C-Leg 4. The primary outcome variable for this study was the summed joint mechanical work of the remaining joints, inclusive of the sound leg and intact hip on the amputated leg. Overall, the Power Knee showed advantages with this metric for stair ascent compared to the passive devices with a net reduction compared to the Rheo of 14.1% (step-over-step gait) and a net reduction of 23.3% compared to the C-leg (step-by-step gait). Surprisingly, the C-Leg was found to have a lower biological energy (p<0.05) than the Power Knee during ramp ascent, as the Power Knee did not add significant mechanical energy to the gait during ramp ascent. There were no significant differences between the three knees during ramp and stair decent, indicating that choice of MPK is not important for descent activities. Our results did not find any significant differences between the Rheo or C-leg in terms of joint energies across ramps and stairs. For the Power Knee, apparent benefit was observed for stair ascent over the other MPKs, but it under-performed the C-leg for ramp ascent.
An additional aim of this thesis study was to provide an evaluation of the modeling of the Open Source Leg (OSL), a research-grade powered device. The model was validated for inverse kinematics and dynamics during ramp ascent and it was found to be more accurate than the previously used Able Body model. The validated results were then compared to the commercial MPKs to identify if the OSL provided an advantage during ramp ascent. An apparent benefit was observed as the OSL had a lower summed biological joint work than all three commercial MPKs and significantly lower than the Power Knee.
This thesis study covers the experimental procedures performed, an analysis of the results and a discussion of the findings in these two aims.
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2023-05-02
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