The Effects of Porcine Extracellular Matrix Nerve Wrap as an Adjunct to Primary Epineurial Repair
Philip J Hanwright, MD1; Jennifer Rath, BS2; Nicholas von Guionneau, MBBS1; Sai Pinni, BS1; Benjamin Slavin, BS3; Dan A Zlotolow, MD4; W.P. Andrew Lee, MD1; Jaimie T Shores, MD5; A. Lee Dellon, MD1; Sami H. Tuffaha, MD5
1Johns Hopkins University School of Medicine, Baltimore, MD, 2University at Buffalo Jacobs School of Medicine and Biomedical Sciences, Buffalo, NY, 3University of Miami School of Medicine, Miami, FL, 4Shriners Hospital for Children, Philadelphia, PA, 5Department of Plastic and Reconstructive Surgery, Johns Hopkins University School of Medicine, Baltimore, MD
Background: The use of nerve wraps has been advocated as a means of protecting and isolating the neurorraphy site; however, there is a paucity of data to support their use. The most commonly used commercially-available nerve wrap is an extracellular matrix (ECM) membrane derived from porcine small intestine submucosa (AxoGen, Alachua, FL). The purpose of this study is to characterize the effects of using this wrap as an adjunct to primary epineural repair. Methods: Lewis rats were randomized to undergo median nerve transection and epineural suture repair either with or without the use of a wrap around the coaptation site (n=10 per group). Animals were sacrificed at five weeks for quantitative histologic analysis of intraneural scar formation and inflammatory cell infiltration at the repair site, as well as distal axonal regeneration and neuromuscular junction reinnervation. These groups were repeated with a 15-week endpoint to allow for weekly assessments of functional recovery with grip strength testing. Results: The wrapped group demonstrated significantly less intraneural collagen deposition at the coaptation site at five weeks (65.6±2.7% vs 52.4±3.5%, p=0.01) (Figure 1). There were no statistically significant differences between the wrapped and unwrapped groups for inflammatory-cell density, the number of regenerating axons, or percent reinnervation of neuromuscular junctions at either endpoint. (Table 1). Initial functional recovery occurred sooner in the wrapped group than the unwrapped group (5 weeks vs. 6 weeks, p=0.090). At the 15-week endpoint, there was no statistically significant difference between the wrapped and unwrapped groups (1.29±0.12N vs. 1.06±0.10N, p=0.17) grip strength compared to baseline, respectively (p=0.346, Figure 2). No deleterious effects were observed with use of the wrap. Conclusion: The use of the porcine ECM nerve wrap as an adjunct to primary epineurial repair is safe and effective in reducing the rate of intraneural collagen deposition at the neurorrhapy site. Trends towards modest improvement in inflammatory cellular infiltration, motor reinnervation and functional recovery were noted that did not reach statistical significance.
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