Sensory feedback from body-powered and myoelectric prostheses are limited, but in different ways. Currently, there are no empirical studies on how incidental feedback differs between body-powered and myoelectric prostheses, or how these differences impact grasping. Thus, the purpose of this study was to quantify differences in grasping performance between body-powered and myoelectric prosthesis users when presented with different forms of feedback. Nine adults with upper limb loss and nine without (acting as controls) completed two tasks in a virtual environment. In the first task, participants used visual, vibration, or force feedback to assist in matching target grasp apertures. In the second task, participants used either visual or force feedback to identify the stiffness of a virtual object. Participants using either prosthesis type improved their accuracy and reduced their variability compared to the no feedback condition when provided with any form of feedback (p<0.001). However, participants using body-powered prostheses were significantly more accurate and less variable at matching grasp apertures than those using myoelectric prostheses across all feedback conditions. When identifying stiffness, body-powered prosthesis users were more accurate using force feedback (64% compared to myoelectric users' 39%) while myoelectric users were more accurate using visual feedback (65% compared to body-powered users' 53%). This study supports previous findings that body-powered prosthesis users receive limited force and proprioceptive feedback, while myoelectric prosthesis users receive almost no force or proprioceptive feedback from their device. This work can inform future supplemental feedback that enhances rather than reproduces existing incidental feedback.

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Extracting motor signals directly from the peripheral nervous system poses challenges in obtaining both high amplitude and sustainable signals for upper-limb neuroprosthetic control. To translate peripheral nerve interfaces into the clinical space, these interfaces must provide consistent signals and prosthetic performance. Previously, we have demonstrated that the Regenerative Peripheral Nerve Interface (RPNI) is a biologically stable, bioamplifier of efferent motor action potentials. Here, we assessed the reliability of the RPNI signals in humans for long-term prosthetic control. RPNI signal quality, measured as signal-to-noise ratio, remained greater than 15 for up to 276 and 1054 days in participant 1 (P1), and participant 2 (P2), respectively. Though signal amplitude varied between sessions, P2 maintained prosthetic performance above 94% accuracy for 604 days without recalibration. Additionally, P2 completed a real-world multi-sequence coffee task with 99% accuracy 611 days without recalibration, demonstrating the potential of RPNIs as a long-term interface for enhanced prosthetic control.

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bstract. Objective. Electrical stimulation can induce sensation in the phantom limb of individuals with amputation. It is difficult to generalize existing findings as there are many approaches to delivering stimulation and to assessing the characteristics and benefits of sensation. Therefore, the goal of this systematic review was to explore the stimulation parameters that effectively elicited referred sensation, the qualities of elicited sensation, and how the utility of referred sensation was assessed. Approach. We searched PubMed, Web of Science, and Engineering Village through January of 2022 to identify relevant papers. We included papers which electrically induced referred sensation in individuals with limb loss and excluded papers that did not contain stimulation parameters or outcome measures pertaining to stimulation. We extracted information on participant demographics, stimulation approaches, and participant outcomes. Main results. After applying exclusion criteria, 49 papers were included covering nine stimulation methods. Amplitude was the most commonly adjusted parameter (n = 25), followed by frequency (n = 22), and pulse width (n = 15). Of the 63 reports of sensation quality, most reported feelings of pressure (n = 52), paresthesia (n = 48), or vibration (n = 40) while less than half (n = 29) reported a sense of position or movement. Most papers evaluated the functional benefits of sensation (n = 33) using force matching or object identification tasks, while fewer papers quantified subjective measures (n = 16) such as pain or embodiment. Only 15 studies (36%) observed percept intensity, quality, or location over multiple sessions. Significance. Most studies that measured functional performance demonstrated some benefit to providing participants with sensory feedback. However, few studies could experimentally manipulate sensation location or quality. Direct comparisons between studies were limited by variability in methodologies and outcome measures. As such, we offer recommendations to aid in more standardized reporting for future research.