Investigation of a tri-articular mechanism in reducing energy expenditure in passive transfemoral prostheses
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Date
2024-12
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University of New Brunswick
Abstract
Efficiency in human gait is dependent on coordination of muscle movements to provide a transfer of energy. Individuals with transfemoral amputations using a passive prosthesis lose efficiency in gait due to disruption of the flow of energy through the leg. By exploring joint coupling between the hip, knee, and ankle, transfemoral prostheses could be designed that improve user energy expenditure. This work investigated the hypothesis that by coupling joint motion through the leg, a passive transfemoral prosthesis can be designed that uses prosthetic joint motion to provide improved energy transfer; thus reducing user hip energy during gait.
The hypothesis was explored through three specific aims of design, optimization, and testing. A transfemoral prosthesis was designed that implemented a tri-articular mechanism linking the motion of the hip and ankle. A simple five link walking model was adapted to implement prosthesis parameters, based on the developed prototype and used for co-optimization of the tri-articular spring stiffness and intact joint torques. The function of the developed tri-articular mechanism was explored in a pilot study, where increasing spring stiffness provided increasing prosthetic assistive torque. The results of each phase contributed to knowledge in the field surrounding the passive implementation of tri-articular joint coupling and co-optimization of a tri-articular spring and user joint torque.
The findings of the three aims supported the hypothesis that joint coupling can be used as a means of energy transfer in a transfemoral prosthesis while demonstrating the need for future research. Optimization of the walking model showed the tri-articular spring parameter was weakly convex and could not be optimized in tandem with all four intact joints but could be optimized with one intact joint. In testing the developed tri-articular mechanism, the prosthesis motion allowed energy to be stored in the tri-articular spring, but the energy was not successfully transferred to the user. Results suggested that energy transfer to the user from work done by the assistive torque is dependent on the timing of energy release from the prosthesis spring. Future study is needed to evaluate the hypothesis and determine how to optimize a tri-articular mechanism to reduce user energy expenditure.