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Despite decades of research, the development of prosthetic limbs has not moved forward significantly in the last 40 years. Current devices do not provide sensory feedback to the user and are not easy to control, which can leave amputees struggling to cope with everyday tasks.
Now a consortium of engineers, neuroscientists and clinicians have come together in the EU-funded DETOP project to provide upper-limb amputees with a significant step change – a sophisticated prosthesis that can be directly controlled by their thoughts.
The human ‘touch’
A range of complementary technologies has been developed through DETOP. Key to the new system is the project’s innovative ‘osseointegrated human-machine gateway’ (OHMG) which physically links a person to their prosthesis.
The OHMG – developed by one of DETOP’s key partners Integrum SA – is directly fitted to bones in the user’s arms during a surgical procedure. It forms a stable base for the prosthetic limb and enables electrical communication between the prosthesis and electrodes which are also implanted in the person’s body. A patient in Sweden had the first OHMG implanted in an operation that took place in December 2018.
The project has also developed a mechatronic coupler which will allow a patient to move his or her prosthetic hand to a natural position. Furthermore, DETOP has built a new lightweight prosthetic hand, complete with an embedded controller and tactile sensors. The goal is to provide the user with feedback from their new hand that provides close to natural sensations of touch and movement.
‘Over the coming months, the patient who received the OHMG will start to use a training prosthesis before being fitted with our new artificial hand,’ explains DETOP consortium member Francesco Clemente from Prensilia Srl, Italy. ‘We will then assess the entire system – including the implanted interface, electronics, wrist and hand controls – as the patient goes about his or her daily activities.’
The assessment will include standard occupational therapy tests to check hand functions as well as specific tests designed by the project team to measure motor coordination and grip strength.
Natural control and movement
‘The implant gives us a unique opportunity to study how the brain communicates with the new hand. Control should be very natural – for example, the patient should be able to think of moving the index finger and the index finger should move on that command,’ adds project coordinator Christian Cipriani from Scuola Superiore Sant'Anna, Italy. ‘There are still many steps to be taken, but for sure this implant represents the first clinically viable, brain controlled – and felt – prosthetic hand. Reality is quickly moving towards science fiction!’
DETOP plans to follow up this first surgery with more OHMG implants for patients with different types of arm amputations to ensure the system is sufficiently flexible to suit a wide range of potential users.
Work is also continuing on developing integrated circuits capable of collecting bio-signals from users. These circuits are implanted into a person with the aim of making the human-to-machine link even more efficient and responsive.