*Purpose: Despite advancements in understanding and treating peripheral nerve injuries (PNIs), restoration of lost motor and sensory functions remain poor using current methods of clinical repair and management, especially for segmental loss PNIs. In this study, we sought to further optimize current treatment guidelines based on previous success using polyethylene glycol (PEG) to repair segmental-loss PNIs in smaller animal models. Demonstration of successful PEG-fusion repair of segmental-loss PNIs using median peripheral nerve allografts (PNAs) in a porcine model system should enhance transition to clinical trials.

*Methods: Operations for procurement of 15 donor median PNAs (from 8 pre-surgically euthanized Yucatan miniature swine) were performed per IACUC and ACURO approved protocols. Donor PNAs were preserved in a calcium free, hypotonic (260 mM) Normosol solution for 24 or 72-hours before transplantation. Fifteen other Yucatan miniature swine underwent 4-5 cm median nerve (13/15) or ulnar nerve (2/15) segmental resection, followed by prompt epineural neurorrhaphy with the preserved viable PNAs. Animals were randomly divided into 4 treatment groups. Group 1 (n=3): Control; Group 2 (n=4): PEG + methylene blue (MB); Group 3 (n=4): PEG + MB + methylprednisolone; and Group 4 (n=4): PEG + MB. MB was added to nerve ends, sutured, and covered with PEG for 2 minutes (± local steroid administration over surgical site). Animals in Groups 1-3 used a 24-hour preserved viable median PNA for reconstruction while PNAs in group 4 were preserved for 72-hours. Each recipient animal received electrodiagnostic evaluations and routine assessment of porcine gait with videography before and after nerve reconstruction. Animals were followed up for 14 days after nerve transplantation and then sacrificed. PNAs were removed at this time while preserving the sutured sites by transecting 1-2 cm proximal and 1-2 cm distal of the donor PNA. The procured nerves were sent for histological analysis.

*Results: Electrodiagnostic and morphometric evaluations were performed. Initial analyses show: (1) flexor carpi radialis muscle activation upon electrical stimulation correlating with positive compound muscle action potential (CMAP) waveforms, and (2) axonal survival in PEG-treated donor PNAs and distal host median nerves in PEG treated swine compared to control swine not PEG-treated.

*Conclusions: Preliminary data indicates the potential success of PEG-fusion protocols to enhance recovery from segmental-loss PNIs.

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