Jana D. Moon

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

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 Interface for Prostheses Control: Electrode Comparison.

BACKGROUND This study compared epimysial patch electrodes with intramuscular hook electrodes using monopolar and bipolar recording configurations. The purpose was to determine which strategy transduced muscle signals with better fidelity for control of myoelectric prostheses. METHODS One of the two electrode styles, patch (n = 4) or hook (n = 6) was applied to the left extensor digitorum longus muscle in rats. Electrodes were evaluated at the time of placement and at monthly intervals for 4 months. Evaluations consisted of evoked electromyography signals from stimulation pulses applied to the peroneal and tibial nerves in both monopolar and bipolar recording configurations. RESULTS Compared with hook electrodes, patch electrodes recorded larger signals of interest and minimized muscle tissue injury. A bipolar electrode configuration significantly reduced signal noise when compared with a monopolar configuration. CONCLUSION Epimysial patch electrodes outperform intramuscular hook electrodes during chronic skeletal muscle implantation.

Abstract 17: prototype sensory regenerative peripheral nerve interface for artificial limb somatosensory feedback.

total of 85 patients completed the primary outcome assessments, 47/49 patients in the study group and 38/44 in the control group. Seventy-one patients had DIEP flaps and 14 patients had free muscle-sparing TRAM flaps. There were 11 postoperative complications (13%), 7 in the treatment group, 4 in the control group, and none was related to TAP catheter, and there were no flap failures. Randomization resulted in a balanced distribution of patients, and there were no differences in age, BMI, clinical or demographic characteristics between the two groups. For the primary outcome, the reduction in parenteral morphine consumption was only significantly different between the two groups on POD 1. In the Bupivacaine group, the mean parenteral morphine consumption was 20.7 (SD=20.1) mg compared to 30.0(SD=19.1) mg in the placebo group (p=0.02) on POD 1. There were no differences between the two groups in any of the secondary outcomes measures.

Quantification of muscle-derived signal interference during monopolar needle electromyography of a peripheral nerve interface in the rat hind limb

High-fidelity signal acquisition is critical for the fundamental control of a neuroprosthesis. Our group has developed a bio-artificial interface consisting of a muscle graft neurotized by a severed nerve in a rat hind limb model. This regenerative peripheral nerve interface (RPNI) permits nerve signal transmission, amplification, and detection via in situ electromyography (EMG). Our study examined the magnitude of signal interference from simultaneously contracting muscles adjacent to our muscle of interest. In eighteen F344 rats, the extensor digitorum longus (EDL) muscle was used to fabricate simulated RPNI constructs of various sizes in which the neurovascular pedicle was preserved, obviating the need for reinnervation or revascularization. After 3 weeks of recovery, in situ EMG testing was performed using electrical stimulation of the common peroneal nerve. A recording needle was placed in the EDL muscle with a reference/ground electrode in the contralateral toe webspace, comprising a monopolar recording configuration. The superficial peroneal nerve was transected to further isolate stimulation of the anterior compartment. Recordings from the EDL were performed before and after excision of the tibialis anterior (TA) and extensor hallucis longus (EHL) muscles. After TA/EHL excision, EDL compound muscle action potential (CMAP) peak-to-peak amplitudes were significantly lower by an average of 7.4±5.6(SD) mV, or 32±18%, (paired t(17)=-5.7, p<;0.0001). A significant positive linear correlation was seen between CMAP amplitude and EDL mass both before TA/EHL excision (r=0.68, n=18, p<;0.01) and after TA/EHL excision (r=0.79, n=18, p<;0.0001). EDL mass did not correlate with differences in CMAP amplitude or area caused by TA/EHL excision. Monopolar needle EMG recordings from the EDL muscle are significantly, but predictively, contaminated by concomitant muscular contractions in the anterior compartment of the rat hind limb. Further investigation of strategies to reduce this signal interference, including electrode choice or configuration, use of bioelectrical insulators, and filtering methods, is warranted to promote high-fidelity signal acquisition for prosthetic control.

Abstract 61: Characterization of Regenerative Peripheral Nerve Device Signaling during Evoked Maximal and Submaximal Fatiguing Conditions.

PurPose: Regenerative peripheral nerve interface devices (RPNI devices) transduce signals between remaining peripheral nerves of a residual limb and motorized prostheses. RPNI devices consist of a transferred muscle neurotized by a transected peripheral nerve with electrodes secured to the muscle for RPNI signal transduction. RPNI device maximal twitch signaling has been characterized; however, device function during repetitive signaling has not been studied. Our purpose was to characterize RPNI device continuous submaximal signaling including fatigability with respect to measures of maximal signal.

Abstract 60: Signal Strength, Reliability, and Validity of Active Regenerative Peripheral Nerve Interface Device Operation during Voluntary Movement

PurPose: Regenerative Peripheral Nerve Interface (RPNI) devices successfully transduce peripheral nerve action potentials to electrical signals suitable for prosthesis control. Voltage changes are the controlling mechanism and can be observed during electromyography (EMG). However, RPNI device signaling has not been characterized during voluntary movements. This study: a) characterizes active RPNI signal strength compared to background activity and b) defines the reliability and validity of RPNI signal function during purposeful movements.

Von Frey monofilament testing successfully discriminates between sensory function of mixed nerve and sensory nerve regenerative peripheral nerve interfaces

Regenerative peripheral nerve interfaces (RPNIs) transfer motor and sensory signals between amputee and prosthesis. Von Frey (VF) monofilaments are used clinically to evaluate sensory feedback but have not been validated at locations used in our rodent studies. Our purposes were to determine VF sensory test reliability at the ankle and thigh, and to evaluate sensory function of Mixed Nerve (MN) and Sensory Nerve (SN) RPNIs. For reliability testing, VF monofilaments were applied to Normal rats at the ankle and thigh in an up-down pattern. Paw Withdraw Thresholds were determined by alternately exceeding and reducing filament pressure. VF tests were then administered to experimental MN-RPNIs or SN-RPNIs. Reliability results at the ankle showed sensation did not vary over six weeks. At the thigh, reliability was similar during week 0 and 1, but with further testing sensation increased. Comparison between location found at weeks 0 and 1, the ankle was significantly more sensitive than the thigh (p<;0.05). VF administration to experimental animals revealed that the MN-PRNI group was significantly less sensitive than both the SN-RPNI and Normal groups (p<;0.05); while the SN-RPNI and Normal groups did not differ. VF monofilament testing was reliable and successful at distinguishing between sensations of normal skin with dense sensory endings (ankle) and disperse sensory endings (thigh). VF testing successfully discriminated between mixed and sensory nerve RPNI groups.

Complete regenerative peripheral nerve interfaces, fatigue and recovery

Modern technology has taken great strides to restore motion to amputees with prostheses. A key limitation in many cases is lack of a reliable controlling interface to the prosthetic devices. To address this issue, our lab has developed the Regenerative Peripheral Nerve Interface (RPNI). RPNIs transduce signals between residual peripheral nerves, muscle grafts, and prosthetic devices. Prior to this study, RPNIs signal production was primarily evaluated during single evoked maximal action potential. The purpose of this study was to characterize RPNI function during and after repeated submaximal use. RPNIs (n=5) were constructed in a rat model by transferring the EDL muscle from the lower hind limb to the hip region and implanting the transected peroneal nerve into the muscle. Control EDL muscles (n=8) were left in the native location. The muscles were evaluated at least five months postoperatively in terms of maximum evoked compound muscle action potentials, force production, force production during repeated use, and post-fatigue force production. There was a strong correlation between maximum compound muscle action potential amplitude and maximum contractile force (r=0.83 p <; 0.01); thus, force was an indication of signaling. RPNI and Control muscles both fatigued as exponential regressions. Percent post fatigue force production did not differ significantly between the groups, with Controls recovering to 85% of initial maximum force and RPNIs recovering to 60%. RPNIs produce and recover signals in the same relative manner as Controls indicating RPNIs are prime candidates as controlling interfaces for myoelectric prosthetic devices.

Abstract 49: Neuroprosthetic Hand Real-Time Proportional Control by Rodent Regenerative Peripheral Nerve Interfaces

patients experiencing DSWI requiring flap stayed significantly longer in the hospital (28.4 versus 13.3 days, p < 0.001), more often experienced subsequent unplanned readmission (46.5% versus 6.5%, p < 0.001), were more likely to experience 90-day mortality (18.2% versus 5.0%, p < 0.001), and accrued significantly greater healthcare costs (

Abstract 18: real-time proportional control of a neuroprosthetic hand by a rodent regenerative peripheral nerve interface.

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