MICA: Integrated interfacial sensors for assessments of lower limb prosthetics

The research proposed aims to address a technology shortfall that exists in lower limb prosthetics, that is stump-socket loading measurement which is also the single most important unmet need in the field. Without a solution which offers a practical means of dynamic load measurement of the stump-socket interface, determination of socket fit, the single biggest factor determining prosthetic outcomes will remain un-quantified and problematic. The impact of the solution cannot be overstated, as it is likely to yield a paradigm shift in prosthetics care and lead to new knowledge and understanding of the dynamics of stump-socket interface loading.

The aim of the proposed research is to produce a validated "intelligent liner" prototype which provides combined mechanical pressure and shear load measurements at this important loading interface. The intelligent liner will be built around a standard prosthetic liner solution and thus be in a form practical for normal everyday prosthetic use overcoming the practicality deficit of existing pressure only measurement solution. It is important to state in comparison with the proposed solution, existing measurement system exist in a form which are not practical for everyday normal use and are only suitable for short duration laboratory measurement. Furthermore no existing commercialised system has the combined capability of pressure and shear measurement. Shear loading is a fundamental and potentially damaging component of loading at the socket interface which can contribute significantly to tissue damage. This to date while widely known as a significant issue has remained largely un-quantified to the lack of suitable sensing technologies. To get to this prototype, the first objective is to develop a laboratory based stump-socket interface simulator and a system of "control" tests which can be used for liner design optimization. The simulated load tests will be validated from gait analysis measurement to ensure the simulator provides loading which is valid biomechanically and which have a high degree of repeatability and reliability. The next stage is to optimize the intelligent liner design into a form that is practical and can be reliably used in the short to-medium term for loading measurement. The final aims are is to further validate the prototype and combined measurement system taking into account clinical factors that may determine the repeatability of measurements for example such as don/doffing sensor positioning variations. The final outcome is a prototype liner design with combined instrumentation and data visualization which is ready for commercialization. The overall outcome of the project will have demonstrated the technical feasibility of the solution for production on a commercial scale Moreover the intelligent liner design will have been validated for viability through preliminary clinical testing towards commercial clinical product applications.

This 2-year project is designed to develop a practical sensor system that can measure pressure and shear stresses at loaded body-support interface. Such a system can be applied in many biomedical areas associated with the design of insoles, matresses, special seating, assitive rehabilitation robotics, orthotics and prosthetics. In lower limb prosthetics, at the human-machine interface, the socket represents the most critical component for an amputee yet to date its effectiveness is largely unknown due to current unavailability of such a monitoring system. Accordingly, poor socket fit is common and leads to stump pain, ulceration, and secondary amputations. We address this unmet need by exploiting a sensor invention with a filed patent application. We propose to integrate the sensors into intelligent lining/interface materials to deliver a practical system that can monitor loads at the critical stump/socket interface. This will be achieved with 3 proposed milestones, objectives and work packages to cover the development stages of simulator apparatus, sensor system validation, clinical validation and optimization towards user centred product profiles. Scientific and clinical rationale underpinning the proposal have been demonstrated by lab and clinical results. A practical rational is demonstrated by the low cost and integral manner of the proposed system. Such a monitoring system is not currently available on the market. Successful delivery will lead to a new generation of interface systems and a stream of by-products that can be used by prosthetists to assess socket fitting quality, which at present is a largely subjective and iterative process. Additional project delivery will enable advanced monitoring and care tools for amputees to timely adjust socket fit preventing stump tissue damage. The proposed technology represents the first step in delivery of the "holy grail" in prosthetics, namely, a fully automatic self-adjusting socket interface for amputees.

The single most important factor in amputee rehabilitation is comfort and pain reduction at the socket interface. Thus the most direct and immediate beneficiaries of this research socket stump interface sensing will be amputees who will enjoy improved healthcare outcome, quality of life and higher levels of satisfaction with their prosthesis due to improved socket fit. Thus 10s of thousands of amputees in the UK may benefit with millions worldwide. The knock on benefit will be passed to healthcare providers with significant cost reductions arising due to the less frequent occurrences of socket related issues that must resolved within the clinic. The impact of the research will enable down steam research and development towards the "holy-grail" of prosthetics that is a fully automatic and self-adjusting prosthetic socket which can adapt the fit and interface between the stump and socket.

Thus overall there will be a sustained benefit to health care economics in the field of prosthetics in short to medium term in particular. However the wider field of medical device technology will be benefit from of the research as there are countless applications wherever the body is mechanically loaded and where measurement of this loading would be useful to prevent injury. The technology and new knowledge generated by this research will be easily translatable to other applications such as special seating, bedding, and orthotic insoles to name just a few examples. Reduction in occurrences of tissue breakdown and damage due to excessive loading in these scenarios will again provide healthcare economic advantages.

Outside the medical device area, the research output is translatable to other areas, haptic feedback controls in robotics, sports science "the intelligent running track" for sports coaching and development. Instrumented sport wear and equipment. Design and engineering application of seating may benefit with improved comfort and ergonomics "the intelligent seat fit". The users of the research output generated in this project will biomechanists, clinical scientists, tissue engineers and scientists. Sports and ergonomics scientists and technologists.