Electrically stimulated signals from a long-term Regenerative Peripheral Nerve Interface

Abstract

Despite modern technological advances, the most widely available prostheses provide little functional recovery beyond basic grasping. Although sophisticated upper extremity prostheses are available, optimal prosthetic interfaces which give patients high-fidelity control of these artificial limbs are limited. We have developed a novel Regenerative Peripheral Nerve Interface (RPNI), which consists of a unit of free muscle that has been neurotized by a transected peripheral nerve. In conjunction with a biocompatible electrode on the muscle surface, the RPNI facilitates signal transduction from a residual peripheral nerve to a neuroprosthetic limb. The purpose of this study was to explore signal quality and reliability in an RPNI following an extended period of implantation. Following a 14-month maturation period, electromyographic signal generation was evaluated via electrical stimulation of the innervating nerve. The long-term RPNI was viable and healthy, as demonstrated by evoked compound muscle action potentials as well as histological tissue analysis. Signals exceeding 4 mV were successfully acquired and amplitudes were consistent across multiple repetitions of applied stimuli. There were no evident signs of muscle denervation, significant scar tissue, or muscle necrosis. This study provides further evidence that after a maturation period exceeding 1 year, reliable and consistent signals can still be acquired from an RPNI.

Regenerative Peripheral Nerve Interfaces for the Treatment of Postamputation Neuroma Pain: A Pilot Study

“…26,41 Indeed, RPNIs can conduct and amplify nerve signals 44 to support real-time intuitive control of advanced myoprostheses. 45,46 More recent studies have demonstrated muscle reinnervation by sensory nerves as well, which may prove useful in achieving bioprosthetic somatosensory feedback.…”

Regenerative Peripheral Nerve Interface for Prostheses Control: Electrode Comparison

“…The reinnervated muscle prevents neuroma and is a durable site for electrode implantation, thus avoiding iatrogenic axonal injury that can occur when electrodes are directly interfaced with peripheral nerve. 15 We have demonstrated long-term RPNI viability and EMG signal transduction 12,16 ; however, the most appropriate electrode type and recording configuration for high-fidelity signal transduction using RPNIs has not yet been determined. In this pilot study, we evaluated the performance of two of the most accepted electrode designs-an epimysial patch and an intramuscular hook electrode-for signal recording performance during chronic skeletal muscle implantation.…”

“…For purposes of the RPNI, a decrease in signal-of-interest amplitude is not desired; however, signal amplitudes in this study remained sufficiently large to control myoprostheses. 16 Furthermore, small losses of bioelectric signals are acceptable if the signal-to-noise ratio remains high enough such that EMGs responsible for independent functions are easily discriminated from each other.…”

The Evolution of Neuroprosthetic Interfaces

“…Another approach is the regenerative peripheral nerve interface (RPNI), developed by Paul Cederna et al, wherein nerve fascicles are implanted into muscle grafts, each with its own electrode. 179 Although it is still being optimized, RPNI has proven viable for more than a year in a rodent model, with muscle reinnervation and consistently detectable muscle activity during implantation. 179–182 …”

“…179 Although it is still being optimized, RPNI has proven viable for more than a year in a rodent model, with muscle reinnervation and consistently detectable muscle activity during implantation. 179–182 …”