Plastic Surgery Research Council
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PSRC 60th Annual Meeting
Program and Abstracts

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Reliability and Validity of RPNI Signaling of Gait Phases during Voluntary Walking
Andrej Nedic, MSE1; Daniel C. Ursu, MS2; Jana Moon, BS1; Cheryl Hassett, BS1; R. Brent Gillespie, PhD2; Nicholas B. Langhals, PhD1; Paul Cederna, MD1; Melanie Urbanchek, PhD1
1University of Michigan, Plastic and Reconstructive Surgery, Ann Arbor, MI, 2University of Michigan, Mechanical Engineering, Ann Arbor, MI

Introduction: Regenerative Peripheral Nerve Interfaces (RPNIs) are neurotized muscle grafts that control prostheses through electromyography (EMG). RPNI signals have not been quantified during phases of voluntary movements. This study: a) characterizes active RPNI signaling compared to background activity and b) defines the reliability and validity of RPNI function during gait phases of rat walking.
Material and Methods: Rat groups were: Control (n=3), RPNI (n=3), Denervated (n=3). Bipolar electrodes were implanted onto the soleus muscles in each group. The Control group was left intact. The Denervated group had the tibial nerve transected. For RPNIs, the soleus muscle was freely grafted to the ipsilateral thigh and neurotized by the transected tibial nerve. While walking on a treadmill, rats were videographed and raw EMG signals were simultaneously recorded. Outcome measurements were integrated EMG (iEMG) and iEMG normalized (NiEMG) to stance, swing, or sit gait phase.
Results: Majority of EMG activity was observed within the stance phase—70% for Control and 79% for RPNI—as expected for active soleus postural muscles. Stance NiEMG signals were greater than swing NiEMG averages for Control and RPNI groups (Fig 1). The Denervated group stance and swing NiEMG signals were not different without peripheral nerve control. Fidelity of RPNI stance activity (NiEMG signal to background signal) was 5.6 to 1, or double the Control signal fidelity. Correlations between iEMG and stance time for the Control (r=0.74) and RPNI (r=0.76) indicate strong signal reliability (Fig. 2).
Conclusion: Measurements of fidelity, reliability, and validity for RPNI signal detection all exceeded normal probability (p<0.05) during voluntary movement.


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