American Society for Peripheral Nerve
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Promoting Acute Nerve Electrophysiological Recovery Using a 3D Printed Nerve Coupler for Polyethylene-mediated Peripheral Nerve Repair
Chen Shen, MD, MS1; Theodore S. Bronk, BE2; Basile B. Montagnese, BE2; Yutong Xia, BA2; Joshua De La Cruz, BA2; Gracyn J. Campbell, BA2; Justin C. Burrell, PhD3; D. Kacy Cullen, PhD3; Michael K. Matthew, MD1; Jennifer Hong, MD4; Joseph M. Rosen, MD5
1Dartmouth-Hitchcock Medical Center, Lebanon, NH; 2Dartmouth College, Hanover, NH; 3University of Pennsylvania, Philadelphia, PA; 4Dartmouth-Medical Health Center, Lebanon, NH; 5Plastic Surgery, Dartmouth-Hitchcock Medical Center, Lebanon, NH

Introduction Peripheral nerve injury can lead to severe loss of motor control and sensory feedback, resulting in a significant decrease in quality of life for patients. Using traditional approaches for nerve repair, maximal recovery can take up to 2-3 years with fewer than 50% of patients recovering acceptable nerve function. There remains a clear need to improve nerve repair techniques. A major obstacle, especially in proximal nerve injuries, is the natural process of Wallerian degeneration and subsequent nerve regeneration rate of only 1mm/day. We designed and tested a prototype 3D printed nerve coupler device to facilitate nerve repair with polyethylene glycol (PEG), enabling primary nerve fusion at the repair site and restoring electrical functionality in a transected sciatic nerve rat model.
Materials & Methods Device stability and strength were analyzed using finite-element analysis and mechanical testing. Five printed samples underwent maximum force and friction fit testing. The optimal candidate was chosen for in vivo testing. Nine Sprague-Dawley rats were anesthetized, and sciatic nerves were exposed via a split-gluteal muscle approach. Nerves were transected and repaired either using end-to-end epineural suture-only repair (n=3), suture repair with PEG application (n=3), or nerve coupler with PEG application (n=3). Compound nerve action potentials (CNAPs) were measured before and immediately after repair.
Results Finite element analysis revealed maximum stress along friction fit connection points and the center of the coupler. Maximum force the coupler withstood was 45.811.8N, well above mean force applied from surgical tools (8.52.8N). Maximum force required to split each friction fit component was 5.21.7N. Electrophysiology demonstrated normal CNAPs in all animals preinjury. An injury effect was observed in the suture-only repair (106.569.6?V post-repair with 1.90.9% amplitude recovery). CNAP amplitude recovery significantly improved in nerve coupler with PEG application (5047472?V post-repair with 93.720.0% amplitude recovery) when compared to suture repair with PEG application (23511863?V post-repair with 31.415.2% amplitude recovery, p<0.05).
Conclusions The application of tissue engineering principles, especially using fusogens to stimulate cell membrane fusion in axonal discontinuities, can significantly contribute to advancing outcomes in peripheral nerve repair. This proof-of-concept study demonstrates the feasibility of our nerve coupler model for fusogen delivery and rapidly restoring nerve conduction as evidenced by markedly improved CNAP amplitude recovery when compared to standard peripheral nerve epineural coaptation and PEG-assisted fusion alone. Design refinement and long-term physiologic studies are required, but our novel device and methodology is a promising novel approach to surgical repair of peripheral nerve injuries.


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