Objectives

One of the enabling technology of DeTOP is the development of the OHMG for transradial amputees (OHMG-TR). Indeed the previous OHMG design was specific to the transhumeral level where there is a single large bone (humerus), as opposed to two smaller bones at the transradial level (radius and ulna). The OHMG-TR must preserve the successful skin-to-bone sealing interface which has been proven bacteriologically safe.

First man treated with the OHMG System by University of Gothenburg and Integrum in 2013;  DeTOP will build on such interfacing technology.

As opposed to conventional socket attachment, the OHMG-TR does not impair natural (anatomical) wrist rotation. This is one of the great advantages of osseointegration over conventional systems. In turn, long-stump amputees with the OHMG-TR implanted can use their remaining pronator and supinator muscles in order to rotate the wrist whereas short-stump amputees would require a robotic wrist rotator.
The coupling must accommodate different orbit and translational ranges, implant angulations, and share loads equally between the two implants to prevent mechanical failures.

The robotic prosthesis with controllable digit and wrist movements and with embedded sensors is a key enabling technology for the OHMG-TR. Scuola Superiore Sant’Anna has gained significant experience in developing, exploiting and clinically assessing such sensory-equipped robotic hands with a number of interfaces. The prosthesis will include an appropriate number of motorized DoFs for testing the performance of the control interface, as well as tactile and proprioceptive sensors for assessing the feedback part.

The research robotic hand IH2 Azzurra developed by Scuola Sant’Anna and Prensilia; DeTOP will exploit such technology in order to develop a new clinically viable hand prosthesis.

Commercial prostheses are controlled using surface EMG. This type of control can be slow and unintuitive especially in the case of multi degrees of freedom arms and hands. In fact an individual with a transradial amputation with an electric wrist and hand can only control one of them at a time. DeTOP will overcome these limits by accessing the muscles directly and individually through epymisial electrodes through the OHMG-TR. The direct interfacing will allow the holy grail of prosthetic control to be achieved: proportional, simultaneous and physiologically appropriate control could be possible.

Normally limbed subject – wearing an orthopedic splint on the experimental hand – controlling the Azzurra hand using intramuscular EMG signals from physiologically appropriate muscles (Cipriani et al., IEEE TNSRE 2014).

At the perceptual level, the sense of touch is the least understood of the human senses. In DeTOP we will study patterns of neural stimulation that can reliably elicit sensations of varying intensity and character by using a combination of basic research on tactile physiology in volunteers, and directly applying these results to stimulation in chronically implanted electrodes in amputees. Thus, the goal in DeTOP is to go beyond the current, preliminary observations, in order to fundamentally increase our understanding of human tactile sensations in relation to neural coding, and implement functional and natural neural feedback in amputees.

The transhumeral amputee treated with the OHMG undergoing afferent stimulation of mechanoreceptors through microneurography.

DeTOP will develop a miniature node which will be used both for the control of the prosthesis and for sensory feedback. The nodes will be connected to one or several sensors and/or actuators and will be endowed with wireless communication capabilities. A real-time, high-throughput protocol will be designed and tailored to provide the quality of service required by the application, in terms of time constraints, throughput, transfer guarantee.

Miniature PCB developed using technologies from the Centre Suisse d’Electronique et de Microtechnique.

DeTOP aims to carry out three surgical implantations of the OHMG-TR in three selected patients with different levels of transradial amputation, at UGOT clinical centre in Gothenburg, Sweden. The OHMG-TR is a novel device, which requires the development of ad-hoc surgical methods and instruments to secure a safe and successful implantation. Custom designed surgical tools are necessary for guiding the leads safely through the bone without compromising their mechanical integrity, as well as secure mating of the connectors in an expected environment with low maneuverability.