A somatotopic bidirectional hand prosthesis with transcutaneous electrical nerve stimulation based sensory feedback

According to amputees, sensory feedback is amongst the most important features lacking from commercial prostheses. Although restoration of touch by means of implantable neural interfaces has been achieved, these approaches require surgical interventions, and their long-term usability still needs to be fully investigated. Here, we developed a non-invasive alternative which maintains some of the advantages of invasive approaches, such as a somatotopic sensory restitution scheme. We used transcutaneous electrical nerve stimulation (TENS) to induce referred sensations to the phantom hand of amputees. These sensations were characterized in four amputees over two weeks. Although the induced sensation was often paresthesia, the location corresponded to parts of the innervation regions of the median and ulnar nerves, and electroencephalographic (EEG) recordings confirmed the presence of appropriate responses in relevant cortical areas. Using these sensations as feedback during bidirectional prosthesis control, the patients were able to perform several functional tasks that would not be possible otherwise, such as applying one of three levels of force on an external sensor. Performance during these tasks was high, suggesting that this approach could be a viable alternative to the more invasive solutions, offering a trade-off between the quality of the sensation, and the invasiveness of the intervention

Hand Control With Invasive Feedback Is Not Impaired by Increased Cognitive Load

Recent experiments have shown that neural stimulation can successfully restore sensory feedback in upper-limb amputees improving their ability to control the prosthesis. However, the potential advantages of invasive sensory feedback with respect to non-invasive solutions have not been yet identified. Our hypothesis was that a difference would appear when the subject cannot focus all the attention to the use of the prosthesis, but some additional activities require his/her cognitive attention, which is a quite common situation in real-life conditions. To verify this hypothesis, we asked a trans-radial amputee, equipped with a bidirectional hand prosthesis, to perform motor tasks also in combination with a cognitive task. Sensory feedback was provided via intraneural (invasive) or electro-tactile (non-invasive) stimulation. We collected also data related to self-confidence. While both approaches were able to significantly improve the motor performance of the subject when no additional cognitive effort was asked, the manual accuracy was not affected by the cognitive task only when intraneural feedback was provided. The highest self-confidence was obtained when intraneural sensory feedback was provided. Our findings show that intraneural sensory feedback is more robust to dual tasks than non-invasive feedback. This is the first direct comparison between invasive and non-invasive approaches for restoring sensory feedback and it could suggest an advantage of using invasive solutions.ISSN:2296-418

A novel artificial magnetic sphincter to prevent fecal incontinence (preliminary study).

In this research we propose an original magnetic device to strengthen the hypo-atonic anal sphincter and prevent fecal incontinence. METHODS: The device consists in a couple of small magnetic plaques to be surgically inserted in the wall of the anal canal between the external and internal anal sphincters with the opposite polarities face to face, so that, attracting themselves, close the anal lumen. Three couples of magnets made of materials of different magnetic force (neodymium>ferrite>plastoferrite) were evaluated in each of three swine anatomical preparations by measuring the endoanal pressure with a manometric catheter, both before and after magnet implantation. The mean pressures obtained before and after magnet insertion were statistically compared with Student t test. RESULTS: The endoanal pressure after the insertion of neodymium magnets was 79.7+/-13.1 (mean+/-SD), after ferrite magnets was 42.1+/-5.6 mmHg and after plastoferrite magnets was 21.6+/-4.6 mmHg, all of them significantly higher than the pressure recorded in basal conditions (1.72+/-0.71 mmHg). CONCLUSION: This research demonstrated that the implantation of a couple of magnets in the wall of the anal canal is able to create a high pressure zone of a value sufficient to prevent fecal incontinence and that the strength of this "dynamic closure" can be modulated by using magnets of various attraction force, so allowing a "tailored correction" of the anal sphincter hypotension

Shared human–robot proportional control of a dexterous myoelectric prosthesis

Myoelectric prostheses allow users to recover lost functionality by controlling a robotic device with their remaining muscle activity. Such commercial devices can give users a high level of autonomy, but still do not approach the dexterity of the intact human hand. Here we present a method to control a robotic hand, shared between user intention and robotic automation. The algorithm allows user-controlled movements when high dexterity is desired, but also assisted grasping when robustness is paramount. This combination of features is currently lacking in commercial prostheses and can greatly improve prosthesis usability. First, we design and test a myoelectric proportional controller that can predict multiple joint angles simultaneously and with high accuracy. We then implement online control with both able-bodied and amputee subjects. Finally, we present a shared control scheme in which robotic automation aids in object grasping by maximizing the contact area between the hand and the object, greatly increasing grasp success and object hold times in both a virtual and a physical environment. Our results present a viable method of prosthesis control implemented in real time, for reliable articulation of multiple simultaneous degrees of freedom

A closed-loop hand prosthesis with simultaneous intraneural tactile and position feedback

Current myoelectric prostheses allow transradial amputees to regain voluntary motor control of their artificial limbby exploiting residual muscle function in the forearm. However, the overreliance on visual cues resulting from alack of sensory feedback is a common complaint. Recently, several groups have provided tactile feedback in upperlimb amputees using implanted electrodes, surface nerve stimulation, or sensory substitution. These approacheshave led to improved function and prosthesis embodiment. Nevertheless, the provided information remainslimited to a subset of the rich sensory cues available to healthy individuals. More specifically, proprioception,the sense of limb position and movement, is predominantly absent from current systems. Here, we show that sen-sory substitution based on intraneural stimulation can deliver position feedback in real time and in conjunctionwith somatotopic tactile feedback. This approach allowed two transradial amputees to regain high and close-to-natural remapped proprioceptive acuity, with a median joint angle reproduction precision of 9.1° and a medianthreshold to detection of passive movements of 9.5°, which was comparable with results obtained in healthy par-ticipants. The simultaneous delivery of position information and somatotopic tactile feedback allowed both am-putees to discriminate the size and compliance of four objects with high levels of performance (75.5%). Theseresults demonstrate that tactile information delivered via somatotopic neural stimulation and position informationdelivered via sensory substitution can be exploited simultaneously and efficiently by transradial amputees. Thisstudy paves a way to more sophisticated bidirectional bionic limbs conveying richer, multimodal sensation