Plastic Surgery Research Council
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CHARACTERIZATION OF SIGNAL ISOLATION IN BIOTIC AND ABIOTIC RPNI SCAFFOLDS
Presenter: John V Larson, MS
Co-Authors: Kung TA; Urbanchek MG; Cederna PS; Langhals NB
University of Michign

Intro: We have developed a Regenerative Peripheral Nerve Interface (RPNI) for volitional control of bioengineered neuroprostheses. Multiaxial control of individual prosthetic joints requires implantation of multiple proximate RPNIs. Differentiating independent RPNI signals relies on signal isolation techniques, which may require use of a biologically compatible insulating substrate. We investigated the in vivo insulating capacity of small intestinal submucosa (SIS) and silicone.

Methods: In a rat hindlimb model, four groups (N=4/group) were randomly tested using a repeated measures design. A medial gastrocnemius muscle flap was elevated, leaving the neurovascular pedicle intact. The flap was rotated into a chamber containing mineral oil and secured to a silicone base. A stainless steel electrode was affixed to the muscle, and encircled by 1-layer SIS, 4-layer SIS, silicone elastomer, or no covering (control). A superimposing electrode was attached, and an external silicone layer was wrapped around the construct and sutured in place. Electromyographic studies were performed to evaluate the degree of signal isolation between the two electrodes. Data were analyzed using ANOVA and Bonferroni post-test, with p<0.05 significance.

Results: Signal isolation of Compound Muscle Action Potential (CMAP) amplitude at stimulation threshold was significantly greater using silicone (66.728.7%) compared with 1-layer SIS (1.61.9%), 4-layer SIS (1.81.3%), or control (0.91.7%) (p=<0.001). Isolation of CMAP peak-to-peak amplitude at maximal stimulation was also greater with silicone (69.631.1%) versus 1-layer SIS (2.21.5%), 4-layer SIS (1.10.7%), or control (0.10.4%) (p=<0.001). There was no difference in stimulation threshold or muscle latency between groups.

Conclusion: While silicone provides superior signal isolation, it may inhibit revascularization and muscle viability when used as an insulating material for an RPNI. SIS provides minimal isolation acutely, yet provides a structural framework for the RPNI and may enhance tissue integration. Future directions will explore chronic implanted effects on signal isolation.


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