Restoring Natural Sensory Feedback in Real-Time Bidirectional Hand Prostheses

TLDR

Hand loss severely impairs quality of life, and although ideal bidirectional prostheses require reliable intention decoding and near‑natural sensory feedback in real time, current devices lack such feedback. The study aims to provide amputees with rich, natural‑like sensations during grasping to achieve a close replacement of the lost hand. By stimulating median and ulnar nerve fascicles with transversal multichannel intrafascicular electrodes guided by prosthetic sensor data, the authors deliver physiologically appropriate sensory information in real time while decoding grasp tasks to control a dexterous hand. The feedback enabled the participant to modulate grasp force without visual or auditory cues, distinguish three force levels, identify stiffness and shape of three objects, and suggests a keystone strategy for near‑natural hand prostheses.

Abstract

Hand loss is a highly disabling event that markedly affects the quality of life. To achieve a close to natural replacement for the lost hand, the user should be provided with the rich sensations that we naturally perceive when grasping or manipulating an object. Ideal bidirectional hand prostheses should involve both a reliable decoding of the user’s intentions and the delivery of nearly “natural” sensory feedback through remnant afferent pathways, simultaneously and in real time. However, current hand prostheses fail to achieve these requirements, particularly because they lack any sensory feedback. We show that by stimulating the median and ulnar nerve fascicles using transversal multichannel intrafascicular electrodes, according to the information provided by the artificial sensors from a hand prosthesis, physiologically appropriate (near-natural) sensory information can be provided to an amputee during the real-time decoding of different grasping tasks to control a dexterous hand prosthesis. This feedback enabled the participant to effectively modulate the grasping force of the prosthesis with no visual or auditory feedback. Three different force levels were distinguished and consistently used by the subject. The results also demonstrate that a high complexity of perception can be obtained, allowing the subject to identify the stiffness and shape of three different objects by exploiting different characteristics of the elicited sensations. This approach could improve the efficacy and “life-like” quality of hand prostheses, resulting in a keystone strategy for the near-natural replacement of missing hands.