The histological effect of barrier vein wrapping of peripheral nerves

Twenty-four Sprague-Dawley rats underwent exploration and exposure of the sciatic nerve, followed by sham isolation, irrigation, and subsequent wound closure (Group 1); barrier vein wrapping of the nerve using glutaraldehyde-preserved allograft inferior vena cava (Group 2); or barrier vein wrapping of the nerve with femoral vein autograft from the contralateral extremity (Group 3). Four months later, the rats were sacrificed and the nerves fixed in situ in buffered glutaraldehyde. Sections proximal, mid-portion, and distal to the barrier and vein wrap were fixed with osmium tetroxide, epon embedded, stained with toluidine blue, and studied under x200 and x400 light microscopy. Epineural scar formation increased 10 times in Group 2, compared to Group 3 (p < 0.0001). Epineural thickness and the number of degenerating axons did not differ significantly among all groups. Inflammatory cells in Group 2 increased 100 times, compared to Group 3 (p < 0.0001). Continuing with the underlying epineural layer was apparent grossly and microscopically with all allografts, but with no autografts. Thus, glutaraldehyde-preserved allograft vein wraps appear to incite a marked inflammatory response, with epineural scarring and adherence to the underlying nerve, while autograft vein wraps do not.