The restoration of neural sensory feedback in patients with transfemoral amputations was found to improve phantom limb pain, confidence, walking speed, and mental and physical fatigue, according to a proof-of-concept study published in Nature Medicine.

Two patients with transfemoral amputations were implanted with 4 transversal intrafascicular multichannel electrodes designed to signal knee motion and foot placement from the neuroprosthetic device to the residual tibial nerve. Sensations were mimicked from the central metatarsus, lateral metatarsus, and heel to simulate foot placement, and from the calf to stimulate knee flexion. Clinical benefits were assessed by using an outdoor walking test to rank confidence in the prosthetic device, speed of task completion, and mental effort expended. Physical fatigue was assessed by measuring metabolic consumption while walking on a treadmill and outside on grass. Phantom limb pain reduction was assessed by using both frequency-invariant and frequency-variant neural stimulation. All assessments were conducted with and without sensory feedback.

In both participants, self-assessed confidence in prosthetic use and walking speeds during the outdoor walking test were found to increase with sensory feedback (P <.05 for all). A higher mental expenditure during the outdoor walking test was found to be required for walking without vs with sensory feedback. Both participants were able to walk 0.5 km/h faster on the treadmill when sensory feedback was present, with a lower rate of oxygen consumption (P <.05 for both participants). When walking outdoors, one participant had a lower oxygen consumption and the other had a faster pace when sensory feedback was provided, indicating an overall increase in gait efficiency. Reductions in phantom limb pain occurred in both participants during frequency-invariant and frequency-variant 10-minute stimulation sessions (P <.05 for both participants).

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”An investigation longer than 3 months, with a larger cohort of participants, and with in-home assessments, should be executed to provide more robust data to draw clinically significant conclusions about an improvement in the health and quality of life of patients. Fully implantable devices (without transcutaneous cables) need to be developed to allow such investigation. Overall, this work paves the way for the development of a clinical tool that will significantly improve amputees’ health and quality of life,” concluded the investigators.

Disclosure: Several study authors declared affiliations with the pharmaceutical industry. Please see the original reference for a full list of authors’ disclosures.

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Reference

Petrini FM, Bumbasirevic M, Valle G, et al. Sensory feedback restoration in leg amputees improves walking speed, metabolic cost and phantom pain. Nat Med. 2019;25(9):1356-1363.