Histological Comparison of the Fascicular Area of Cabled Sural Nerve Autograft and Processed Nerve Allograft
Fraser J Leversedge, MD1; Bauback Safa, MD2; Walter C. Lin, MD3; Matthew L. Iorio, MD1; Orlando Merced-O'Neill, RN4; Tobias Compos, BS4; Rasa Zhukauskas, MD4; Kasra Tajdaran, PhD5
1University of Colorado School of Medicine, Aurora, CO; 2The Buncke Clinic, The Buncke Clinic, San Francisco, CA; 3The Buncke Clinic, San Francisco, CA; 4Axogen, Alachua, FL; 5AxoGen, Alachua, FL
Purpose: While cabled autografting provides a solution to reconctruct large diameter nerve gaps, it is unknown if it provides regenerating axons with the same amount of regenerative area as a size-matched processed nerve allograft (PNA). The purpose of this study was to provide a direct comparison of the internal fascicular structure or regenerative area of a cabled sural nerve autograft with size-matched PNA in a human cadaveric model.
Method: Six pairs of donor-matched arms (3 female donors, 3 male donors) and six donor-matched legs were utilized for this study. In each arm, the median and ulnar nerves were exposed 30mm ± 10mm proximal from the wrist crease, and a 20mm nerve gap was created. Six median nerves and six ulnar nerves were repaired with cabled autografts constructed from the sural nerves harvested from the donor-matched legs. Six ulnar nerves and median nerves in the second donor-matched arms were repaired using size-matched PNAs. Histological samples from proximal and distal portions of the native nerve and the implanted grafts at each coaptation site were obtained (Fig.1). Cross-sections of the collected tissues were stained with laminin to visualize the fascicles. The total tissue cross-sectional area, the percentage of the fascicular area, and the percentage of the non-fascicular were measured.
Results: The implanted grafts for both ulnar and median nerves had a similar total area compared to the native nerves. PNAs had a significantly higher percentage of fascicular area (%50.5±9.9 in median nerve and %44.9±8.6 in ulnar nerve) compared to the cabled autografts for both median and ulnar nerves (%26.27±5.6, and %25.61±4.9 respectively, p<0.0001). In the median nerve, PNAs had a significantly higher percentage of fascicular area (%50.5±9.9) compared to the native nerve (%35.5±9.6, p=0.001), while the cabled autografts had a similar percentage of fascicular area compared to the native nerve. The results for the percentage of non-fascicular area inversely mirrored that of the fascicular area. PNAs had a significantly lower percentage of non-fascicular area (%49.45±9.9 in median nerve and %55.11±8.6 in ulnar nerve) compared to the cabled autograft (%73.7±5.6, and %74.4±4.9 respectively, p<0.0001).
Conclusion: This histological study using a controlled cadaveric model demonstrated that a size-matched PNA provides a significantly higher percentage of fascicular area or regenerative area for axons compared to cabled autograft reconstruction.
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