Surgically Implanted Electrodes Enable Real-Time Finger and Grasp Pattern Recognition for Prosthetic Hands

Abstract

Currently available prosthetic hands are capable of actuating anywhere from five to 30 degrees of freedom (DOF). However, grasp control of these devices remains unintuitive and cumbersome. To address this issue, we propose directly extracting finger commands from the neuromuscular system via electrodes implanted in residual innervated muscles and regenerative peripheral nerve interfaces (RPNIs). Two persons with transradial amputations had RPNIs created by suturing autologous free muscle grafts to their transected median, ulnar, and dorsal radial sensory nerves. Bipolar electrodes were surgically implanted into their ulnar and median RPNIs and into their residual innervated muscles. The implanted electrodes recorded local electromyography (EMG) with Signal-to-Noise Ratios ranging from 23 to 350 measured across various movements. In a series of single-day experiments, participants used a high speed pattern recognition system to control a virtual prosthetic hand in real-time. Both participants were able to transition between 10 pseudo-randomly cued individual finger and wrist postures in the virtual environment with an average online accuracy of 86.5% and latency of 255 ms. When the set was reduced to five grasp postures, average metrics improved to 97.9% online accuracy and 135 ms latency. Virtual task performance remained stable across untrained static arm positions while supporting the weight of the prosthesis. Participants also used the high speed classifier to switch between robotic prosthetic grips and complete a functional performance assessment. These results demonstrate that pattern recognition systems can use the high-quality EMG afforded by intramuscular electrodes and RPNIs to provide users with fast and accurate grasp control.

Regenerative Peripheral Nerve Interface Surgery: Anatomic and Technical Guide

“…This distinct feature of RPNI surgery to harness discrete motor and sensory signals through reinnervation of multiple individual RPNIs is advantageous when using it as an interface for advanced prosthetic limb rehabilitation. [38][39][40][41][42][43][44][45][46][47]86 There are some limitations with RPNI. Long-term follow-up is still pending.…”

“…RPNI surgery has demonstrated its reliability and durability in harnessing neural signals for neuroprosthetic control. [35][36][37][38][39][40][41][42][43][44] Additionally, RPNI surgery is effective for treatment and prevention of postamputation pain, including both symptomatic neuroma pain and phantom limb pain. 59,[64][65][66][67][68] In the authors' practice, RPNI surgery has also been successful in management of neuromas of superficial sensory nerves particularly in cases of nerve autograft harvest.…”

“…This distinct feature of RPNI surgery to harness discrete motor and sensory signals through reinnervation of multiple individual RPNIs is advantageous when using it as an interface for advanced prosthetic limb rehabilitation. 38–47,86…”

“…RPNI was originally designed as an interface for advanced neural control of prosthetic devices and to overcome the limitations of current control strategies. [33][34][35][36][37][38][39][40][41][42][43][44] RPNI surgery was developed in response to the limitations of existing peripheral nerve electrodes that directly interface with fascicles but yield well-documented adverse sequelae. 35,45,46 Similarly, the use of surface electromyographic signals to drive a prosthetic limb has been associated with poor prosthetic performance.…”

Upper limb prostheses: bridging the sensory gap

“…The regenerative peripheral nerve interface (RPNI) is one novel approach that has the potential to provide both efferent control and afferent feedback from prosthetic devices. The RPNI has been shown in extensive animal studies and human trials to provide high fidelity motor control of prostheses (Irwin et al., 2016; Kung et al., 2014; Urbanchek et al., 2016; Vaskov et al., 2022; Vu et al., 2020). RPNIs are created by wrapping a free skeletal muscle graft around the end of divided peripheral nerves.…”