Lightweight Powered Prosthesis for Above-knee Amputees

Project summary State-of-the-art passive knee and ankle prostheses require unnatural and often strenuous compensatory movements from the residual limb, upper body, and contralateral (intact) leg. Many amputees lack the strength and balance to perform these movements, so they cannot walk freely in the community. Even among younger and stronger amputees, performing these compensatory movements can result in secondary health issues like back pain and osteoarthritis that ultimately limit their mobility and quality of life. Emerging powered prostheses have the potential to address this problem by better replicating the function of the missing biological leg. However, existing powered devices are much heavier than passive prostheses, resulting in increased effort and reduced balance and socket stability. Moreover, their controllers require users to perform unnatural, cumbersome, and frustrating movements. Addressing these limitations is essential to realize the promise of powered prostheses. Our long-term goal is to accelerate the development of prosthesis technologies that provide individuals with lower-limb amputations with unrestricted mobility. The objective of this proposal is to determine the efficacy of a novel lightweight powered knee prosthesis combined with different ankle prosthesis technologies and volitional controllers. Our central hypothesis is that a lightweight powered knee combined with a semi-active ankle powered only for stairs and sit-to-stand will significantly enhance mobility, and electromyographic control will amplify these improvements. To test this hypothesis, our specific aims will assess whether (1) a semi-active ankle that is powered during sit-to-stand and stair climbing and passive during walking is more effective than a powered ankle that is powered during all activities and more effective than a conventional ankle that is passive during all activities, (2) electromyographic control improves mobility by giving users direct voluntary control of the powered prosthesis assistance, and (3) a lightweight powered prosthesis with volitional control can improve mobility in complex home and community environments. The rationale for our proposal is that understanding how different powered prosthesis knee/ankle configurations and control strategies impact mobility will enable the development of improved prostheses and support their clinical prescription and reimbursement, leading to better healthcare, mobility, and quality of life for above-knee amputees. The proposed work is significant because it is the next fundamental step in a continuum of research that is expected to provide clinically viable lightweight powered prostheses that can improve functional mobility and quality of life for above-knee amputees—a population projected to triple by 2050 due to the incidence of peripheral vascular disease. Furthermore, this project is innovative because it challenges clinical practice by proposing the most advanced technologies, in the form of lightweight powered prostheses, as a new standard of care for all above-knee amputees, including older individuals, who commonly undergo amputation due to dysvascular disease and are currently prescribed devices that are considered the least safe and efficient on the market.