Effects of normal or reversed proximodistal orientation of autologous nerve grafts on functional and histomorphological outcomes

Abstract Background: Autologous nerve grafting has been considered the gold standard for the treatment of irreparable nerve gaps. However, the choice of effective proximodistal orientation of autografts (normal or reversed) is controversial. Therefore, we compared functional and histological outcomes between normal and reversed orientations of autografts.Methods: A 10-mm section of the sciatic nerve was harvested from a donor mouse. Half the harvested nerve was grafted onto an irreparable gap in a recipient mouse using either a normal or reversed orientation. The sciatic functional index (SFI) was measured serially for up to 12 weeks postoperatively. Morphological analysis was performed using immunofluorescence staining for neurofilament (NF) and myelin protein zero (P0) in cross-sectional and whole-mount nerve preparations. Additionally, morphological analysis of the tibialis anterior muscle was performed using hematoxylin and eosin staining.Results: The SFI recovered gradually up to 12 weeks after autografting, but there were no significant differences in the SFI between the normal and reversed orientations. The number of NF-expressing axons was significantly higher in the normal orientation than in the reversed orientation. However, there were no significant differences in the number and mean intensity of P0-expressing axons between the orientations. The cross-sectional area of myofibers was significantly larger in the normal orientation than in the reversed orientation.Conclusions: Normally oriented autografts promote axonal regrowth and prevent neurogenic muscular atrophy compared with reverse-oriented autografts. However, despite these positive histomorphometric effects, the proximodistal orientation of the autograft does not affect functional outcomes.