Artificial referred sensation in upper and lower limb prosthesis users: a systematic review

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.