American Society for Peripheral Nerve

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Improving Outcome Following Delayed Peripheral Nerve Grafting: The Application of Photochemical Tissue Bonding and Crosslinked Amnion Nerve Wraps
Neil G. Fairbairn, MD1; Joanna Glazier1; Amanda Meppelink1; Mark Randolph1; Ian Valerio, MD, MS, MBA2; Mark Fleming, DO3; Robert W. Redmond, PhD4 ; Jonathan Winograd1
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 showed that, when applied to large gap injury and nerve grafts, PTB can result in superior outcomes in comparison to suture fixation. Up to now, the success of this technique has only been observed in repairs performed immediately following injury. This rarely occurs clinically and according to some, a delay of several weeks may actually improve regenerative outcome due to clearance of myelin and axonal debris from the distal stump. It was the aim of this study to assess the efficacy of PTB when applied to delayed nerve grafting, and to establish if any additive benefit is detectable in comparison to repairs performed immediately.

Methods: 40 inbred male Lewis rats were randomized into 4 groups (n=10). All 40 rats had 15mm gaps created in their left sciatic nerves. In groups 1 and 2, nerve gaps were repaired immediately with reversed isografts harvested from adjacent rats and fixed with either conventional epineurial suture or PTB, respectively. In groups 3 and 4, repair took place 30-days following injury using reversed isografts harvested from 10 additonal donor rats and fixed with either conventional epineurial suture or PTB, respectively. Outcomes were assessed using monthly walking track analysis and sciatic function index (SFI), gastrocnemius muscle mass retention and nerve histomorphometry. Statistical analysis was performed using ANOVA and the post hoc Bonferroni test.

Results: PTB resulted in greater recovery of SFI following immediate and delayed repair but these results were not statistically significant (-72.3+/-4.7 vs. -68.5+/-4.7; p=0.4 and -80.1+/-4.44 vs. -77.3+/-4.1; p=1). SFI following both suture and PTB was significantly greater when performed immediately rather than after a 30-day delay after injury (-72.3+/-4.7 vs. -80.1; p=0.003 and -68.5+/-4.7 vs. -77.3+/-4.1; p=0.002). Muscle mass retention was significantly greater following PTB fixation in both immediate and delayed repairs (65.1%+/-4.1 vs. 57.8%+/-2.5; p=0.03 and 60.2%+/-4.1 vs. 54.1%+/-5.3; p=0.04). There were no significant differences between immediate and delayed repairs. Histomorphometric analysis is in progress.

Conclusions: PTB results in non-significant improvements in SFI and significant improvements in muscle mass retention in comparison to conventional suture when performed immediately and after a delay of 30-days. Delaying repair for 30-days did not result in any significant additional improvement in outcome. We are hopeful that histomorphometric analysis will support these findings.

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