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

Abstract

Conventional leg prostheses do not convey sensory information about motion or interaction with the ground to aboveknee amputees, thereby reducing confidence and walking speed in the users that is associated with high mental and physical fatigue 1-4 . The lack of physiological feedback from the remaining extremity to the brain also contributes to the generation of phantom limb pain from the missing leg 5,6 . To determine whether neural sensory feedback restoration addresses these issues, we conducted a study with two transfemoral amputees, implanted with four intraneural stimulation electrodes 7 in the remaining tibial nerve (ClinicalTrials. gov identifier NCT03350061). Participants were evaluated while using a neuroprosthetic device consisting of a prosthetic leg equipped with foot and knee sensors. These sensors drive neural stimulation, which elicits sensations of knee motion and the sole of the foot touching the ground. We found that walking speed and self-reported confidence increased while mental and physical fatigue decreased for both participants during neural sensory feedback compared to the no stimulation trials. Furthermore, participants exhibited reduced phantom limb pain with neural sensory feedback. The results from these proof-of-concept cases provide the rationale for larger population studies investigating the clinical utility of neuroprostheses that restore sensory feedback.Despite advances in the development of lower-limb prosthetics 8 , the potential benefits of restoring sensory feedback from such devices to transfemoral (above-knee) or transtibial (below-knee) amputees has not been investigated. 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. designed the study, developed the software and the overall system integration, performed and supervised the experiments, analyzed the data and wrote and reviewed the paper. M.B. performed the surgeries, was responsible for all the clinical aspects of the study and reviewed the manuscript. G.V. developed the software and the overall system integration, performed the experiments, analyzed the data and reviewed the manuscript. V.I. and S. Mazic collected and analyzed the metabolic measurements. P.M. and B.M. collected and analyzed the EEG measurements. P.C. and T.S. developed the TIME electrodes and delivered technical assistance during the implantation and explanation procedures. F.B. and D.B. developed the software and the overall system integration and performed the experiments. N.K. analyzed the data. D.G. and D.A. designed the hardware and embedded software (real-time control) for STIMEP. K.L. and A.A. participated in the experimental design...

Biofeedback Systems for Gait Rehabilitation of Individuals with Lower-Limb Amputation: A Systematic Review

“…Only six studies presented detailed characteristics about the prosthetic components (i.e., prosthetic joint, foot, and socket) utilized to evaluate BFB [34,59,[78][79][80][81]. During BFB testing, most of the participants wore their prescribed prosthesis (i.e., passive mechanical or microprocessor- Table 4 depicts the results of the criteria applied to assess the quality of the reviewed articles.…”

“…During BFB testing, most of the participants wore their prescribed prosthesis (i.e., passive mechanical or microprocessor-controlled knee prostheses). In terms of BFB effectiveness and prosthetic components, the results showed that BFB systems were capable of improving the gait performance of individuals with LLA, regardless of the type of prosthetic components (i.e., passive mechanical knee or microprocessor-controlled knee or powered knee prostheses) [35,59,[79][80][81][82]. FSRs (force sensitive resistors) sensors that were attached to the plantar surface of the prosthetic foot were the most frequently used transducer for measuring the targeted gait parameters.…”

“…Most of the studies did not report any follow-up sessions with the BFB system to test for retention. In addition, few studies evaluated changes on metabolic consumption [34,59], physical fatigue [59], and cognitive load or mental effort [58,59]. Most studies presented positive gait outcomes that were related to one or more physical and physiological parameters.…”

“…It is manifested as sensations or pain from a body part that no longer exists [105]. Techniques, such as mirror therapy and BFB, have demonstrated the potential to reduce phantom limb pain in prosthetic users [59,86,105]. An important benefit of BFB systems when compared to mirror therapy approaches is that, in addition to reducing phantom pain, BFB systems can potentially improve the overall gait performance and prosthetic function of individuals with LLA [59,86].…”

“…BFB approaches in rehabilitation have been studied in a variety of patient populations including stroke [37,[40][41][42], Parkinson's disease [43][44][45], cerebral palsy [46], vestibular deficits [47,48], diabetes [49], and upper-limb [50,51] and lower-limb amputees [31,52,53]. As well as in a variety of applications, including static and dynamic postural balance [54][55][56], walking [57][58][59], stairs management [60], obstacle avoidance [61], floor conditions identification [62], and sensory perception [31,53,63], to mention a few. In 2018, a mapping review [64] was published regarding the use of BFB for gait retraining.…”