Hybrid Electrical-Mechanical Pump for Vacuum Suspension of Prosthetic Sockets

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Prosthetic sockets are secured to the residual limb by a variety of suspension techniques, including mechanical (straps, pin locking liners) and suction (sealing sleeves, one-way valves, vacuum pumps) systems. Evidence strongly suggests the benefit of vacuum-assisted suspension (VAS) over other suspension techniques, including: reducing residual limb volume fluctuations that compromise socket fit, improving gait symmetry, reducing relative motion between the residual limb and socket, facilitating healing of residual limb wounds, and application to prosthesis users with short residual limbs. Commercial pump designs are either mechanical or electrical, each having unique advantages and disadvantages. The Hybrid Integrated Pump Project Initiative (HIPPI) began in 2010 as part of a Department of Defense funded project and resulted in the design of pump technology that incorporates electrical and mechanical systems to achieve VAS irrespective of the state of the user while maximizing battery life and minimizing noise. The HIPPI technology underwent preliminary evaluation demonstrating feasibility but highlighting the need for additional enhancements. The purpose of this project is to further design and evaluate the HIPPI system and enhance commercial-viability to attract industry partners with whom to generate a market-ready device through future collaborative efforts. This device would have considerable value for the Veterans Health Administration by offering technology that would apply to active patients who desire rapid generation of VAS with minimal battery recharging, and older patients who rely on sustained VAS without the need to continuously load their prosthesis. While our design has attracted interest from multiple prosthetics manufacturers, design improvements must be made to enhance commercial-viability and ensure efficacy of use in persons with amputation. These needs will be addressed through the development activities of this work including stage-gate design processes, bench and human subject testing, and input from stakeholders. We plan to refine the hybrid electrical-mechanical vacuum pump design by: 1) optimizing the mechanical pump system to ensure generation of a maximum level of vacuum comparable to existing vacuum pumps, and 2) seamlessly integrating a microprocessor-controlled electrical pump system to monitor vacuum level and reengage the system when pressure falls below a set minimum. During the design process, industrial design and user-centered market research will be conducted through stakeholder focus groups and consultation with an industrial designer and our industry partner to enhance commercial viability. Each iterative prototype of the HIPPI system will undergo bench and human subject testing. The electrical system will be bench tested to quantify the time and rate by which the system achieves the minimum-required vacuum level in a sealed volume, and verify that the microprocessor recognizes when the level falls below a predefined value and activates to reestablish that level. The mechanical system will be bench tested to quantify the number of cycles to achieve sufficient vacuum level and verify that the device satisfies structural ISO 10328 standards (static strength and durability). A prototype will also be assessed on individuals with below-knee and above-knee limb loss in the laboratory to verify that the pump can achieve and sustain sufficient vacuum level between the prosthetic liner and socket during walking but does not considerably alter socket reaction moments. The deliverable from this project will be a refined and working HIPPI prototype that will be applicable to Veteran users of VAS irrespective of their age, gender, or activity level. The results of this work will position us well to transfer this technology to a commercial partner and engage with them in competitive research proposals to continue commercialization efforts and evaluate clinical efficacy in large-scale VA clinical studies.