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Signals from Adjacent RPNIs are Independent during Voluntary Walking
Andrej Nedic, MBE, Ian C. Sando, MD, Daniel C. Ursu, MS, Jana D. Moon, BS, Cheryl A. Hassett, BS, Brent R. Gillespie, PhD, Nicholas B. Langhals, PhD, Paul S. Cederna, MD, Melanie G. Urbanchek, PhD.
University of Michigan, Ann Arbor, MI, USA.

PURPOSE
Regenerative Peripheral Nerve Interfaces (RPNIs) are neurotized muscle grafts that transduce peripheral nerve action potentials to electrical signals for prosthesis control. Each RPNI controls a single movement. The purpose of this study was to determine whether adjacent RPNIs controlling antagonistic activity provide independent signaling.
METHODS
In RPNI rats, tibialis anterior and extensor digitorum longus (EDL) muscles were grafted to the left thigh, implanted with bipolar electrodes, and neurotized with transected peroneal and partial tibial nerves, respectively. In Control rats, the left EDL and soleus muscles were implanted with permanent electrodes. Rats (n=4) were videographed during treadmill walking; electromyography (EMG) signals were simultaneously recorded. Gait phases were synchronized with EMG activity.
RESULTS
EMG activity for RPNI and Control rats displayed periodic patterns of activation alternating between antagonist muscles during left leg swing and stance phases (Fig 1). During swing phase, there was greater EMG activity from peroneal nerve-innervated muscles than tibial nerve-innervated muscles for both RPNI and Control groups (p<0.001); during stance phase, there was greater EMG activity from tibial nerve-innervated muscles than peroneal nerve-innervated muscles (p<0.001). Out of 32 stepping cycles, agonist and antagonist RPNIs were activated during the expected gait phase 97%.
CONCLUSIONS
Adjacent RPNIs demonstrated independent signal activation with high specificity during voluntary walking. These data support RPNI independence and RPNI use to provide agonist/antagonist control for myoelectric prostheses.
Acknowledgment: DARPA (N66001-11-C-4190).


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