Introduction Without meaningful and intuitive sensory feedback, even the most advanced myoelectric devices require significant cognitive demand to control. Critical to the design of an ideal bioprosthetic device is the development of a single interface between human and machine that allows for transmission of both afferent somatosensory information and efferent motor signals for device control. The Composite Regenerative Peripheral Nerve Interface (C-RPNI) is a novel biologic interface that demonstrates promise in this role. The C-RPNI is a surgical construct composed of a transected, mixed motor and sensory peripheral nerve implanted between a composite free graft consisting of de-epithelialized glaborous skin and skeletal muscle. The purpose of the present study was to investigate the viability and bidirectional signal transduction capabilities of the C-RPNI.
Materials & Methods: C-RPNIs were surgically implanted on the end of divided common peroneal nerves of twelve F344 rats using free skeletal muscle grafts obtained from the animal's contralateral limb, and de-epithelialized dermal grafts harvested from glaborous skin of donor rat hindpaws. At six months, electrophysiologic testing was performed to determine both the in vivo efferent and afferent signal transduction capabilities of C-RPNIs following electrical stimulation. At study endpoint, C-RPNI constructs were harvested for histologic evaluation.
Results: C-RPNI constructs remained viable over the study period with regeneration and revascularization evident on histologic analysis. Electrical stimulation of proximal peroneal nerve evoked efferent signals (CMAPs) and muscle contractions that were measured from the free muscle graft component of the C-RPNI. Average CMAP amplitude recorded from the muscle was 6.1 ± 1.6 mV with an average conduction velocity of 12.0 ± 2.0 m/sec. Electrical stimulation of the dermal side of the C-RPNI evoked afferent signals (CSNAPs) in the proximal peroneal nerve. Average peak-to-peak CSNAP amplitude was 267.1 ± 143.8 µV with an average conduction velocity of 9.6 ± 2.4 m/sec.
Conclusion: C-RPNI constructs remained viable with preserved innervation for 6 months following implantation. The C-RPNI facilitates bidirectional signal transduction of both efferent motor signals and afferent sensory signals. This confirmation of bidirectional signal transduction in the C-RPNI validates the potential role of the C-RPNI in human-machine interfacing.