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The Application of Photochemical Tissue Bonding and Acellular Nerve Allograft for Large Gap Nerve Injury
Neil G. Fairbairn, MD1; Joanna Glazier, MD1; Amanda Meppelink1; Mark Randolph1; Ian Valerio, MD, MS, MBA2; Mark Fleming, DO3; Robert W. Redmond, PhD4; Jonathan Winograd, MD1
1Plastic and Reconstructive Surgery, Massachusetts General Hospital, Boston, MA; 2Division of Plastic and Reconstructive Surgery, University of Pittsburgh Medical Center, Pittsburgh, PA; 3Department of Orthopaedics and Rehabilitation, Walter Reed National Military Medical Center, Bethesda, MD; 4Wellman Centre for Photomedicine, Massachusetts General Hospital, Boston, MA
Introduction: Photochemical tissue bonding (PTB) creates sutureless, watertight bonds between two apposed tissue surfaces that have been stained with photoactive dye and illuminated with a 532nm laser. Building on previous success in end-to-end repair, we have recently shown that, when applied to large gap injury requiring nerve grafting, PTB can result in superior outcomes in comparison to conventional suture fixation. Following major multi-limb injury and amputation, demand for autogenous nerve graft may exceed that which can be supplied by the patient. Acellular nerve allograft (ANA) is an alternative option in these circumstances although outcomes are typically inferior to autograft. It is the aim of this study to assess the efficacy of PTB when used with ANA.
Methods: 20 sciatic nerves were harvested from Sprague Dawley rats and sent to AxoGen Inc for processing. An additional 20 male inbred Lewis rats were randomized into 2 groups (n=10). All rats had 15mm left sciatic nerve defects created and repaired with processed ANA. 1 group had nerves secured using conventional epineurial suture. The remaining group had ANA secured using PTB. Following surgery, walking track analysis was performed at monthly intervals and sciatic function index (SFI) calculated. Following sacrifice after 150-days, repaired nerves were excised for histomorphometric analysis. Left (experimental) and right (control) gastrocnemius muscles were excised for calculation of muscle mass retention. Statistical analysis between groups was performed using the unpaired t-test.
Results: Sciatic function index did not differ significantly between standard repair and PTB groups after 5-months follow up (-80.3+/-4.2 vs. -78.3+/-5.0 respectively; p=0.3). Following sacrifice, all nerves were in continuity and, on gross observation, showed evidence of regeneration. Those nerves repaired photochemically had less extraneural scar tissue formation in comparison to standard epineurial suture. Gastrocnemius muscle mass retention did not differ significantly between standard repair and PTB groups (53.3%+/-6.9 vs. 55.2%+/-5.5 respectively; p=0.5). Histomorphometric analysis is in progress.
Conclusion: Although PTB has proved superior to conventional suture when used for isograft fixation, this advantage appears to be lost when applied to ANA. The beneficial effects of PTB likely relate to its ability to create a water-tight seal, preventing the leakage of neurotrophic factors. The absence of schwann cells and other cellular components in ANA may reduce the impact of this effect and explain the observed loss of efficacy in this study. PTB remains an alternative, rapid method of fixation for end-to-end nerve repair and nerve graft reconstruction.
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