The DeTOP project targets people with reduced or absent hand sensorimotor capabilities, due to an amputation. The latter is known to cause severe physical and psychosocial dysfunction. Besides the obvious inability to grasp and manipulate objects, as well as to sense the environment through the sense of touch and proprioception, the hand may no longer be used for gestures that normally support speech and emotional expressions. Additionally, the physical differences compared to other people can result in severe psychological problems. DeTOP aims to develop the next-generation transradial prosthesis by clinically implementing robotic, sensing and long-term interfacing technologies.
Core of the system is an osseointegrated human-machine gateway (OHMG), able to create bidirectional links between a human and a robotic prosthesis. The OHMG is an enhancement of the OPRA Implant System (by Integrum AB, Sweden). The latter consists of two main components, the fixture and the abutment, mechanically secured by a screw so that the loads are directly transferred between the prosthesis and the skeleton. The OHMG also allows for bidirectional electrical communication, between the prosthesis and electrodes in the body (Fig. 1). Hence this system can provide direct electrical access with peripheral neuromuscular structures of the body, using suitable electrodes. For example, myoelectric signals recorded using epymisial electrodes can be collected and used for controlling a prosthesis; vice-versa cuff electrodes can convey sensory feedback to the brain, using an external stimulator connected to tactile sensors in the hand. Because of these unique features, today the OHMG is probably the most advanced technique for bidirectional neuromuscular interfacing, suited for the upper limb amputees, which was proven functional in the long term. Notably, the first recipient of the OHMG system is a patient with a trans-humeral amputation which was implanted in January 2013 – since then is using it. This successful case paved the way for DeTOP and now opens the door for the study and implementation of more natural and complete prostheses.
The goal of DeTOP is to push the boundaries of this technology –made in Europe– and to make it clinically available to the largest population of upper limb amputees, namely transradial amputees. This objective will be targeted by developing a novel prosthetic hand with improved functionality, smart mechatronic devices/features for safe implantable technology, and by studying and assessing paradigms for natural control (action) and sensory feedback (perception) of the prosthesis through the OHMG.
DeTOP will not only develop ready-to-use human-machine-interfaces and dexterous prostheses for the disabled; the interfaces and systems developed within the project will be chronically implanted in selected patients which will take the systems at home.
The overall concept underpinning the project is shown in Fig. 2. The 3 scenarios share the same modular design and are composed of six main blocks in order to handle parallel streams of efferent (control signals – dependent on user’s intent) and afferent (sensory feedback signals – based on artificial senses in the prostheses) information. Starting from the human body the six blocks are: (1) the implanted electrodes, (2) the OHMG-TR, (3) the recording/stimulation electronics, (4) the processing and communication nodes, (5) the mechatronic coupler and (6) the hand/wrist prosthesis with proprioception and tactile sensors.
