Design and In Vivo Testing of an Anatomic 3D-Printed Peripheral Nerve Conduit in a Rat Sciatic Nerve Model

Peter S Chang; Tony Y Lee; David Kneiber; Christopher J Dy; Patrick M Ward; Greg Kazarian; John Apostolakos; David M Brogan

doi:10.1177/15563316241299368

Design and In Vivo Testing of an Anatomic 3D-Printed Peripheral Nerve Conduit in a Rat Sciatic Nerve Model

HSS J. 2024 Nov 22:15563316241299368. doi: 10.1177/15563316241299368. Online ahead of print.

Authors

Peter S Chang¹, Tony Y Lee², David Kneiber³, Christopher J Dy⁴, Patrick M Ward⁵, Greg Kazarian⁶, John Apostolakos⁷, David M Brogan⁴

Affiliations

¹ Department of Orthopaedic Surgery, Vanderbilt University Medical Center, Nashville, TN, USA.
² School of Medicine, Saint Louis University, St. Louis, MO, USA.
³ Department of Anesthesiology, Keck School of Medicine of USC, University of Southern California, Los Angeles, CA, USA.
⁴ Department of Orthopaedic Surgery, School of Medicine, Washington University, St. Louis, MO, USA.
⁵ Department of Orthopaedic Surgery, University of Chicago, Chicago, IL, USA.
⁶ Hospital for Special Surgery, New York, NY, USA.
⁷ Department of Orthopaedic Surgery, Case Western Reserve University, Cleveland, OH, USA.

Abstract

Background: Three-dimensional (3D) printer technology has seen a surge in use in medicine, particularly in orthopedics. A recent area of research is its use in peripheral nerve repair, which often requires a graft or conduit to bridge segmental defects. Currently, nerve gaps are bridged using autografts, allografts, or synthetic conduits. Purpose: We sought to improve upon the current design of simple hollow, cylindrical conduits that often result in poor nerve regeneration. Previous attempts were made at reducing axonal dispersion with the use of multichanneled conduits. To our knowledge, none has attempted to mimic and test the anatomical topography of the nerve. Methods: Using serial histology sections, 3D reconstruction software, and computer-aided design, a scaffold was created based on the fascicular topography of a rat sciatic nerve. A 3D printer produced both cylindrical conduits and topography-based scaffolds. These were implanted in 12 Lewis rats: 6 rats with the topographical scaffold and 6 rats with the cylindrical conduit. Each rodent's uninjured contralateral limb was used as a control for comparison of functional and histologic outcomes. Walking track analysis was performed, and the Sciatic Functional Index (SFI) was calculated with the Image J software. After 6 weeks, rats were sacrificed and analyses performed on the regenerated nerve tissue. Primary outcomes measured included nerve (fiber) density, nerve fiber width, total number of nerve fibers, G-ratio (ratio of axon width to total fiber width), and percent debris. Secondary outcomes measured included electrophysiology studies of electromyography (EMG) latency and EMG amplitude and isometric force output by the gastrocnemius and tibialis anterior. Results: There were no differences observed between the cylindrical conduit and topographical scaffold in terms of histological outcomes, muscle force, EMG, or SFI. Conclusion: This study of regeneration of the sciatic nerve in a rat model suggests the feasibility of 3D-printed topographical scaffolds. More research is required to quantify the functional outcomes of this technology for peripheral nerve regeneration.

Keywords: conduit; nerve conduit; nerve injury; nerve surgery; peripheral nerve conduit; peripheral nerve injury.