Currently, the most advanced prosthetics on the market use technology that is more than four decades old. The challenge for today’s scientists and engineers is to develop a more dextrous prosthetic limb that can help amputees carry out more of the tasks that others take for granted.
The EU-funded INPUT project focuses on improving the control of the complex upper limb prostheses – such as those for hands and arms – making it more effortless and intuitive. With everyday use in mind, the project team is transferring promising results obtained in laboratory settings into clinically and commercially viable products. To save development time and minimize costs, the researchers have married new technologies with existing prosthetics hardware.
INPUT’s consortium of academic, industrial and clinical partners has made advances in areas such as signal acquisition and processing to improve prosthetic movement. All activities are user focused and include training with amputees.
‘Our project is providing the electronics and software to measure and decode muscle activity,’ said INPUT project coordinator Sebastian Amsüss of Otto Bock Healthcare Products in Austria. ‘We have also come up with training methods to help amputees use the INPUT system, as well as a means to assess how individuals perform tasks when using their prosthetic.’
Although the project does not finish until 2020, solid results have already been achieved. In an important breakthrough, the team has designed an electrode liner.
‘The liner is like a sleeve that is put over the existing part of a limb – for example the forearm of someone who has lost a hand,’ explains Amsüss. ‘It contains all the electrodes and electronics necessary to measure muscle activity. We have managed to make a liner of reliable quality and consistent thickness – and we can make it in different sizes.’
INPUT has also developed a new pattern recognition algorithm and related software, which are used to decode muscle activity. These innovations allow muscle signals from the residual limb that are picked up by the electrode liner to be processed into movement commands. This artificial neural network vastly outperforms anything currently on the market.
Training is key to ensuring that INPUT produces technology that is practical, robust and meets the needs of users. To that end, the project has developed two games that allow prosthetic users to get used to their control devices.
One involves collecting boxes and controlling a ball on paths that become narrower as the user advances. The other tests the ability to grip and catch falling objects. In addition, a mobile body tracking application has been developed to quantify how someone using the INPUT devices performs a task compared to non-amputees.
INPUT is now running a large clinical study to compare its technologies to the state-of-the-art in arm prosthetics.
‘Clinical insight and use of the INPUT system with real amputees is a key factor for successful implementation, validation and ultimately commercial adoption of prosthetic devices,’ says Amsüss. ‘We have already enrolled seven people and are targeting a total of around 20 to 25. In the field of arm prosthetics this is a large study – 95 % of all research papers published have one to three people.’
The project team is preparing to commercialize some of the products emerging from INPUT, such as the electrode liner, the games and the recognition algorithm.