Six‐Month Assessment of a Hand Prosthesis with Intraneural Tactile Feedback

Abstract

Objective: Hand amputation is a highly disabling event, which significantly affects quality of life. An effective hand replacement can be achieved if the user, in addition to motor functions, is provided with the sensations that are naturally perceived while grasping and moving. Intraneural peripheral electrodes have shown promising results toward the restoration of the sense of touch. However, the long-term usability and clinical relevance of intraneural sensory feedback have not yet been clearly demonstrated. Methods: To this aim, we performed a six months clinical study with three trans-radial amputees who received implants of transverse intrafascicular multichannel electrodes (TIMEs) in their median and ulnar nerves. After calibration, electrical stimulation was delivered through the TIMEs connected to artificial sensors in the digits of a prosthesis to generate sensory feedback, which was then used by the subjects while performing different grasping tasks. Results: All the subjects, notwithstanding their important clinical differences, reported stimulationinduced sensations from the phantom hand for the whole duration of the trial. They also successfully integrated the sensory feedback into their motor control strategies while performing experimental tests simulating tasks of real life (with and without the support of vision). Finally, they reported a decrement of their phantom limb pain and a general improvement in mood state. Interpretation: The promising results achieved with all subjects show the feasibility of the use of intraneural stimulation in clinical settings.

Sensory feedback restoration in leg amputees improves walking speed, metabolic cost and phantom pain

“…2a-c). Other less physiologically plausible percepts such as tingling, pulsation and electricity were evoked, similarly to previous reports with the same technology 13 , which were not used for the neuroprosthesis and pain tests. The extent of the sensations was localized and did not change (or changed only slightly) when the injected charge in the tibial nerve was varied (Extended Data Fig.…”

“…Location and extent could be drawn on an illustration of the foot and leg. Intensity was reported on a scale from 0 to 10 (as in Petrini et al 13 ). Participants could also freely make a description of the elicited sensation, if needed.…”

“…Most surgery techniques 9 and noninvasive methods 10-12 to restore sensory feedback have been tested only in transtibial amputations, which produce a less disabling clinical condition than transfemoral amputation 1,3 . Direct neural stimulation through transversal intrafascicular multichannel electrodes (TIMEs) 7 has enabled upper-limb amputees to feel touch sensations from the missing hand and to exploit them for long-term prosthesis control 13,14 . Only F.M.P.…”

“…a few trials 15,16 with direct nerve stimulation that did not show clear benefits for the leg amputees have been conducted. Restoring sensory feedback from the phantom hand of upper-limb amputees through neural stimulation has been shown to decrease phantom limb pain (PLP) 13,17,18 . However, the efficacy of low-frequency nerve stimulation 19 has never been investigated for treating PLP in leg amputees.…”

Implantable Neural Interfaces and Wearable Tactile Systems for Bidirectional Neuroprosthetics Systems

“…Petrini et al successfully performed long‐term clinical studies over 6 months in three transradial amputees where four intraneural TIME (14 active site each) were implanted in median and ulnar nerves. Electrode placement, impedance and stimulation threshold charge remained steady over 25 weeks; in particular impedance for two patients remained stable at ≈80 and ≈70 kΩ over time without any notable statistically significant change, while for the third patient it stabilized after 3 weeks at 40 kΩ.…”