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Assistive Technology Sensor Platform


OBJECTIVE: Develop advanced sensor technologies that allow for the prosthesis socket and/or prosthetic components to respond to signals from the residual limb based on sensing from within the socket at the residual limb interface. Develop the ability to place sensors comfortably, safely and unobtrusively within the intimate confines of the socket-limb interface. Design and build ruggedized, low-cost, lightweight, non-invasive, unobtrusive sensors and a nonproprietary (open) platform-based system architecture for component-based, device-agnostic sensing that will eventually collect and share data to any number of current and future prosthetic devices. While this topic may appear technology-centric, the ultimate objective is to facilitate a comfortable, high-definition, high-fidelity, high-capability socket that will allow the user the user a more comfortable socket which also enables a much higher level of functionality and responsiveness from the prosthetic system. DESCRIPTION: Major limb amputations are among the most debilitating wounds sustained by those who survive a combat injury [1]. Recent military operations in Iraq and Afghanistan have resulted in a significant increase in the number of traumatic amputees receiving care in the military medical system [2,3]. Additionally, based on current population estimates for the United States (US), there are over 1.5 million people living with limb loss [4] with an incidence of 1 in 200 persons. Given our ageing population and increases in lifestyle diseases, it has been projected that the number of people living with limb loss will more than double by the year 2050 to 3.6 million primarily as a result of amputation secondary to dysvascular disease [5]. People with limb loss or limb deficiency use prosthetic and orthotic devices to regain function and mobility and restore appearance. Prostheses and Orthoses are externally applied devices used to replace wholly, or in part, an absent or deficient limb segment (ISO 8549-1, 1989). Prosthetic sockets form the interface between the residual limb and the prosthesis and are important for the transmission of forces and distribution of pressure in persons with amputation [6]. Conformity of the socket to the residual limb is extremely important, leaving negligible room for sensors to be inserted [6]. Existing sensor technologies are often too bulky and rigid to be accommodated comfortably and safely within the intimate fit of the prosthetic socket. Additionally, they are often limited to sensing only one variable. The challenge is to develop a sensor platform that is flexible, unobtrusive, and can be configured with almost any existing sensor. Advanced prosthetic technologies that respond to physiologic information from the residual limb require improved sensor platforms to become realistic, everyday solutions for the functional restoration of persons with amputation. An improved sensor platform could also be used to create monitoring systems for improved residual limb health and increase knowledge of the interface environment that should spur further developments in prosthetic systems. An improved and unobtrusive sensor platform could also be used to provide exteroceptive data as well, enabling the device or system to respond accordingly to external conditions. The Assistive Technology Sensor Platform will apply existing and/or innovative sensing technology for measurement of modalities such as pressure, shear, temperature, moisture, electromyography (EMG), limb volume, etc. that would be required for extended daily usage. The prosthetic sensing platform will enable integration with new sensors and new prosthetic components without undue redesign of either. The envisioned prosthesis-agnostic nonproprietary (open) sensing platform should comprise at least the following components: Sensors. Development of sensors suitable for guiding operation of a prosthesis, such as pressure, strain and temperature sensors. Sensors must operate effectively in the hot, moist environment of a prosthetic socket, in close proximity to human tissue, for extended periods of time. Open Integration Platform. Development of nonproprietary (open) architecture for sensor and device integration, data processing and pattern recognition to prosthetic devices, in such a manner that third-party prosthesis and sensor developers can more easily integrate and test products for compliance with the platform. The continuous capture, storage and transmission of sensor data will be critical to the operation of advanced prosthetic technologies. Requirements of the sensor platform system include: Unobtrusiveness, comfort and durability for extended use in a prosthetic socket in close proximity to tissue; Ability to integrate component sensors to measure the properties of interest in prosthetic applications (pressure, shear, temperature, moisture, blood flow, tissue oxygenation, EMG, limb volume, etc.); Ability to model data input characteristics of sensors and sensor arrays; Fidelity, accuracy and spatial/temporal resolution; Durability (especially within the socket environment); Means of managing and delivering power to a sensor array. It may be assumed that the prosthesis will have its own power source that can be used by the sensor system (e.g. couple with scavenger technology, inductive charging through liners and sockets.); Means of buffering and communicating data with prosthesis at rates and bandwidths sufficient to support dynamic control algorithms; Evidence of a scalable path to affordability and reasonable replacement costs for long term use. PHASE I: Develop sensor prototype and overall platform-based system architecture design that includes specification of sensor- and prosthesis-agnostic data management, calibration, signal processing, data storage, monitoring, network connections and power management. Demonstrate operation and data communication from candidate sensors under field-relevant laboratory conditions in three or more independent sensing modalities (pressure, shear, temperature, moisture, EMG, limb volume, etc.) needed to supply data for prosthetic control system. PHASE II: Develop and demonstrate a prototype sensing system for human testing with prototype or commercially available test prostheses. Demonstrate operation closed-loop sensor management under field-relevant conditions in six or more independent sensing modalities (pressure, shear, temperature, moisture, blood flow, tissue oxygenation, EMG, limb volume, etc.) in a spatially-distributed array, needed to supply data for prosthetic control system. Demonstrate rapid integration of one or more third party or research sensors. Conduct testing to demonstrate feasibility over extended operating conditions. Demonstrate plan for FDA approval. Across similar capabilities, demonstrate that this technology offers a greater level of comfort then traditional intra-socket sensing technologies. PHASE III DUAL USE APPLICATIONS: Demonstrate a path toward scalability and transition of a nonproprietary platform-based sensing architecture for integration with current and future prosthetic devices. Propose a methodology for application, use, calibration, maintenance and replacement of sensing devices for continuous operation of prosthetic systems over long periods of time, with estimations of lifecycle costs. Develop hardware and software-based development kits suitable for customizing third party products, while maintaining and prioritizing patient comfort and functionality. REFERENCES: [1] L. Stansbury, et al.,"Amputations in U.S. Military Personnel in the Current Conflicts in Afghanistan and Iraq,"J Orthop Trauma, 22(1), 43-46 (2008). [2] P. Pasquina, K. Fitzpatrick,"The Walter Reed Experience: Current Issues in the Care of the Traumatic Amputee,"Journal of Prosthetics and Orthotics, 18(Proceedings 6), 119-122 (2006). [3] H. Fischer,"U.S. Military Casualty Statistics: Operation New Dawn, Operation Iraqi Freedom, and Operation Enduring Freedom,"Congressional Research Service Report for Congress, September 28, 2010. [4] P. Adams, G. Hendershot, and M. Marano,"Current estimates from the National Health Interview Survey", National Center for Health Statistics (1996 and 1999). [5] K. Ziegler-Graham, E.J. MacKenzie, P.L. Ephraim, T.G. Travison, R. Brookmeyer,"Estimating the prevalence of limb loss in the United States: 2005 to 2050,"Archives of Physical and Medical Rehabilitation, 89, 422-9 (2008). [6] A.F. Mak, M. Zhang, and D.A. Boone,"State-of-the-art research in lower-limb prosthetic biomechanics-socket interface: a review,"Journal of Rehabilitation Research and Development,"38(2), 161-74 (2001).
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