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Natural Integration of Bionic Limbs via Spinal Interfacing

Periodic Reporting for period 1 - Natural BionicS (Natural Integration of Bionic Limbs via Spinal Interfacing)

Reporting period: 2019-06-01 to 2020-11-30

Loss of a limb is a devastating experience that substantially affect the quality of life, social integration, and capacity to work. Current solutions for replacing missing limbs with artificial counterparts are not satisfactory for patients with amputations, as demonstrated by the fact that amputees often decide to abandon the use of advanced prosthetics. The main weaknesses in the current technological solutions are related to a poor regain of function, to the lack of any sensations from the artificial limbs, and to the rigid design of robotic limbs which limit natural interaction with the environment. These problems have remained the same for decades.

In this situation of high technological challenges and translational stagnation, Natural BionicS aims at creating a fully integrated, symbiotic replacement of missing or damaged parts of the human body with artificial limbs that the user will feel and command as a true part of her/his body. This aim will be achieved by a breakthrough concept of bidirectional interfacing with the spinal cord and integration with soft robotics, based on the combined expertise in surgical probing (Medical University of Vienna), interfacing (Imperial College London), and soft robotics (Italian Institute of Technology). The novel concept consists of surgically creating bio-connectors (bio-hub) to access the spinal cord circuitries by using biological pathways of encoding (sensation) and decoding (motor commands) neural information. The surgical bio-hub will allow bidirectional information flow from and to the spinal cord with direct interface with revolutionary robotic limbs that are designed for soft and natural mechanical interaction with the environment.

The final aim of Natural BionicS will be reached through the achievement of four sub-objectives (SOs):
SO1 (Surgery): Surgical creation of a bio-hub that provides access to the sensory-motor representation of the missing limb;
SO2 (Interfacing): Establishment of a high-information transfer input-output flow by accessing the bio-hub;
SO3 (Robotics): Design of soft robotic arms/hands/legs that embed kinematic synergies and variable stiffness joints;
SO4 (Integration): Establishment of a full correspondence of the sensory-motor image of the limb at the bio-hub with the robotic limb.

The technology developed during Natural BionicS will also have a broader impact into other medical and non-medical areas, such as in interfacing for stroke rehabilitation, monitoring development in neonates, and wearable large-scale interfaces.
The workplan has been followed closely and the activities are on time with respect to the plan (see Annex). The work progresses in the different areas are briefly summarised in the following while details are provided in the scientific publications:

- Surgery. An animal model of multiple nerve transfers into a single muscle has been developed and validated with extensive electrophysiological measurements. Multi-channel implanted EMG systems have been used in this animal model to decode the activity of motor neurons from the multiple innervating nerves (see progress in Interfacing below). Moreover, an animal model of skin graft and sensory reinnervation has also been developed and tested.
- Interfacing. A simulator of intramuscular electrical activity has been designed to generate synthetic signals modelling motor neuron activity as generated by multiple innervating nerves. Thin-film electrodes consisting of linear arrays of 40 electrodes have been designed and tested in the animal models described above. A two-dimensional array grid electrode has been designed and manufactured by the company Cortec for animal use. Real-time decomposition methods for high-density EMG have been developed, tested, and validated.
- Robotics. The main progress has been on the design, manufacturing and test of a soft robotic hand actuated by two kinematic synergies, which constitutes an important step forward in the development of limbs with natural interaction with the environment and requiring advanced control signals. Progresses have also been done in the design of robotic wrists and elbows and in variable stiffness actuators. Soft foot prostheses have also been finalised and preliminary tested in patients.
- Integration. A clinical bionic board has been established at the beginning of the project to initiate the integration of the activities and patient recruitment. The board consists of the project PIs and senior members of the three research teams. The clinical bionic board has met regularly at the Medical University of Vienna from the beginning of the project until March 2020, when personal meetings had to be interrupted due to the pandemic. Nonetheless, meetings continued to be held regularly in a remote setting. Interaction of the three teams has been extensive and has already determined the publication of 4 joint articles between PIs. Measures on patients by the three teams with integration of the technologies developed so far have been performed since the beginning of the project.

In addition to the progresses described above, all teams have further exploited the developed technologies in additional application areas. For example, the robotic hands have been applied in pioneering studies on stroke rehabilitation, the EMG decoding systems in the study of neonatal development and in spinal cord injury patients, and the surgical nerve transfer methods have been translated into a new paradigm for treating spasticity.
In the first 18 months of the project, important scientific achievements have already been reached. This is documented in detail in the list of publications. The quality of the research and the substantial advance of the state of the art is clearly testified by the quality of the published research (which include papers in the New England Journal of Medicine, Nature Biomedical Engineering, Science Robotics, Science Advances, as well as core engineering Journals, such as Transactions of the IEEE). The research highlights are: the development of breakthrough methods for multiple nerve transfer into a single muscle to establish a high information transfer from the spinal cord to the target muscle (here used as bioscreen); the design of AI-based decoding algorithms that process muscle signals and extract the activity of the innervating nerve fibres; and the design of multi-synergy soft robotics. These developments have already been published in top Journals in the respective fields. It is expected that the next period of the project will see a much greater integration of the individual advances into highly innovative systems that combines the breakthroughs in the three disciplines.
Project goal - a bidirectional prosthetic interface for revolutionary robotic limbs