Novel Bio-Inspired 'Smart' Joint for Prosthetics and Robotics Lower Limbs

At present there are over 90,000 new cases of knee replacements and leg amputations every year in the UK alone. This is equivalent to approximately one every six minutes. Currently between 5 - 6,000 major limb amputations are performed in the UK each year and trauma accounts for approximately 55% of them. Lower limb amputation has a profound effect on activities of daily living and not all amputees are able to tolerate or use a prosthesis. Therefore, it is essential that the prosthesis is comfortable and adapted to be used by patients in order to enhance their daily activities. Artificial knee joints are important medical devices that enable many people to maintain walking and running functions. In working towards this target, researchers have repeatedly missed the key role held by the correlation between the soft tissues (ligaments) and the structure (bones) in human-like locomotion. Biological joints demonstrate multi-functionality by integrating high conformity, compactness and low friction. These functions are crucial when designing a functional and robust joint by including this separation of functions at the conceptual stage.

Though there is still little known about the exact implications and mechanisms involved while performing human movement, recent engineering research into the mechanics of the ligaments and the analysis of the knee joint in compression has produced models and simulations that have shed light on some of the possible roles of the human knee features. Therefore, we believe that this separation of functions into the design process of prosthetic joint is essential to facilitate design optimisation.

Researchers are actively engaged in developing wearable devices including prosthetics that are increasingly embedding control and electronics sub-systems making them more autonomous and 'smarter'. On the other hand, limitations on space and power mean that artificial limb joints (for robots or prosthetics) must be highly optimised for mechanical performance in areas such as stiffness, strength, friction, mechanical advantage, backlash and endurance.

Current trends in the design of artificial lower limbs, ranging from robotic articulations to prostheses for lower limb amputees, favour the utilisation of engineered joints, which typically are composed of a pin joint containing a hinge-pin and ball bearings. Particular prosthetic knee joints (polycentric) contain four-bar mechanisms in order to produce a moving centre of rotation as is the case with the human knee. There are two main categories of control for prosthetic knee joints - microprocessor control (use of an electronic unit, evaluating and making internal adjustments to control the motion) and mechanical control (use of a mechanical hinge, automatically controlled by the mechanism).

The main purpose of this work is to further the state-of-the-art in prosthetics design and lower robotic limbs for transfemoral (above knee) amputees and humanoids robots in areas relevant to artificial devices and their uses for locomotion including walking, climbing stairs, squatting and also stability. This research will combine the relationship between three areas: the technological advancements of lower robotic limbs, knee implant design for total knee replacement, and the emergence of 'smart' prosthetics.

In this two-year programme, we will investigate the feasibility and development of a novel bio-inspired prosthetic joint that will exploit the key and beneficial features of human knee joint. This research will be achieved by featuring a progressive bottom up approach towards the design and test of the bio-inspired 'smart' joint. A comparative investigation with respect to human performance (energy consumption and gait efficiency) between the novel bio-inspired joint against current prosthetics provided by the industrial partners will be undertaken with the contribution of a para-triathlete gold medallist in the Rio Paralympics 2016.

The project PI will manage the dissemination/exploitation of the scientific and technical results from this project with the aid of the Co-Is and the resources available from their respective institutions including the Bristol Robotics Laboratory (BRL), University of the West of England (UWE), University of Bristol (UoBr), University of Bath (UoBa) and Imperial College London (ICL) that have very extensive media engagement and Science Communication Units. These will be fully engaged with the bio-inspired 'smart' joint research. Additionally, the two collaborative academic partners will each be responsible for the execution of dissemination/exploitation activities, with assistance and guidance from industrial partners Össur Ltd and Ottobock Ltd industries.

Each academic partner will aim to publish a number of refereed journal articles within the project duration. These articles will help raise awareness on new technology developments. As the project progresses into year two, consideration will be given to organising Special Sessions at leading Conferences and Special Issues in Journals.

The design of artificial limbs attracts a great deal of media attention. The BRL will draft several press releases and distribute them to media outlets, such as publishers of local and national newspapers. BRL will take responsibility for coordinating joint press release activities. Additionally, the PI plans to disseminate some of the work at the Science Fair in Bath and at two seminars on Novel Mechanical and Electrical Technology. Opportunities to be involved in outreach activities through the Science Communication units will be evaluated and taken further when appropriate. The BRL is also partner with At-Bristol which will be in regular contact to disseminate when possible. Additionally and prior to start this project, a para-triathlete gold medallist in the Rio Paralympics 2016 is already in contact through one of the industrial partners with the PI and he is willing to contribute to the research for WP2 (design process) and WP3 (testing and comparison of performances).

Towards the end of the project we plan to run a workshop at an internationally recognised event. Two examples of suitable events are: the Int Conf on Rehabilitation Robotics or Int Conf on Complex Medical Engineering. Moreover, the consortium will apply for a booth at the European Robotics Forum and at the Academy Annual Meeting and Scientific Symposium. These exhibitions will allow demonstration of the results of the project to a wide audience, and to closely interact with the best industrial and academic scientists in the world.

We have already undertaken a review of the potential range of applications of the device and gathered reactions from the two advanced industries that will be involved with the development of the bio-inspired 'smart' joint; direct skeletal prosthesis (Osseointegration) and lower limb exoskeleton research groups as fabrication sources and polycentric knee prosthetic manufacturers as end-users of the device. This list will be extended and utilised as the project proceeds, with guidance from industrial partners Össur Ltd and Ottobock Ltd industries.

The PI and partners expect some significant patentable inventions to arise during the course of the project. The industrial partners in the consortium intend to protect commercially significant inventions resulting from the project by further patent applications. Areas not patented, which the consortium wants to submit to the procedure for patenting, may be kept confidential for a period of time agreed by the PI in conjunction with Co-Is.
This programme is the beginning of a new research area to the BRL's portfolio. After completing this project, the PI plans to create an 'Artificial Lower Limb' group at the BRL wherein similar collaboration of experts to the one developed during this programme will be extended to other joints and applications.