The Effects of Normal or Reverse Orientation of Autografts on Functional and Histological Outcomes Following Autogenous Nerve Grafting
Jung Il Lee, M.D, Ph.D, Korea University Guro Hospital, Seoul, Korea, Republic of (South), Duk Hee Lee, M.D, Ph.D, Ewha Womans University Mokdong Hospital, Seoul, Korea, Republic of (South) and Jong Woong Park, Professor, MD, PhD, Korea University Anam Hospital, Seoul, Korea, Republic of (South)
Introduction: Autologous nerve grafting has long been considered as the gold standard for treatment of irrepairable nerve gaps. However, the effective orientation of the nerve grafts, either proximal to distal as normal and reverse, is remained controversial. We compared functional and histological outcomes between normal and reverse orientation of the nerve grafts.
Materials and Methods: Nerve gap-grafting injuries were performed on female C57BL/6 mouse (10 weeks old; n = 10/group) under surgical microscope. A 10 mm length of sciatic nerve was harvested from each of the donor mouse. Irrepairable nerve gap was created on the recipient mouse by dissecting 3 mm of sciatic nerve. The half (5 mm) of harvested nerve sections from the donor mouse were grafted on the recipient mouse in either normal or reverse orientation and repaired with fibrin glue at the both ends. Motor functional recoveries from the surgeries were monitored by walking track analysis biweekly up to 12 weeks after injury. After 12 weeks, morphological analysis of the nerve was performed by immunofluorescent staining for neurofilament (NF) heavy chain and myelin protein zero (P0) in cross-sectional and whole-mount nerve preparations. Additionally, morphological analysis of the tibialis anterior muscle was performed by Hematoxylin and eosin staining.
Results: All the grafted mouse had significantly better sciatic functional index than the donor mouse; however, there was no significant differences between grafting in the normal and reverse orientation (12 weeks; donor, -86.6±2.1; normal, -59.6±4.1; reverse, -64.5±1.9). Fluorescence microscopy of cross-sectional nerve grafts revealed that the number of NF or P0-expressing axons and the ratio of P0/NF-expressing axons were higher in group with grafting in the normal orientation than in the reverse orientation. However, the differences were not statistically significant. Confocal microscopy of the whole-mount nerves revealed that the number of NF-expressing axons in the middle and distal portion of nerve graft were significantly higher in the normal orientation than the reverse orientation group (the middle; normal, 1246.5±117.7; reverse, 808.3±87.5, distal; normal, 1216.3±106.5; reverse, 838.5±61.9; P < 0.05). The CSA of myofibers was significantly larger in the normal orientation than in the reversed orientation (P<0.05). However, the minimum Feret's diameter of the myofibers were no significant differences between the normal and reverse orientation group.
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.
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