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ASRM Fascicular Turnover Nerve Flaps Versus Free Nerve Grafts: Pilot Study of Comparison and Outcomes in a Rat Model
Adrian Ooi, MBBS, Terence Goh, MD; Chin-Ho Wong, MD; Kok Chai Tan, MD
Plastic, Reconstructive and Aesthetic Surgery, Singapore General Hospital, Singapore, Singapore
Introduction
Free nerve grafts (FNG) are the gold standard for bridging nerve gaps. However, outcomes are unpredictable and donor site morbidity is incurred. Koshima et al reported promising results with the fascicular turnover nerve flap (FTF). This involves dissection of individual fascicles from injured nerves, severing that fascicle, turning it over and matching it to a fascicle from the opposite end (Fig. 1). Evidence for this technique has been anecdotal. We performed the FTF in a rat model to compare the efficacy of this technique with the FNG.
Fig. 1: FTF from the proximal to the distal nerve ending of the gap.
Methodology
22 Wistar rats had sciatic nerve gaps of 4-5mm created in their left hind legs. 7 received FNG, 13 received FTF (Fig. 2), and 2 rats were used as controls. Follow-up consisted of functional testing using the Extensor Postural Thrust (EPT) and Sciatic Functional Index (SFI). At the end of the 8-week study period histopathological studies were done.
Fig. 2: FTF on rat left sciatic nerve
Results
Functional
EPT studies (Table 1) showed improvement in percentage motor deficit of the experimental to the normal side for the FTF, with rate of recovery comparable to the FNG. SFI calculations showed similar improvement in function.
Table 1: EPT showing return to function of the FTF and the FNG groups.
Histopathological
At 8 weeks, nerve sections proximal and distal to the FTF portion were cut. On H&E (Fig. 3), proximal nerve endings display structured axons enveloped by myelin, while at the distal nerve end in addition to axons with myelin there are clumps of nerve sprouts, showing evidence of regeneration. Special stains (Fig. 4) confirm re-myelination.
Fig. 3: H&E – proximal nerve ending showing axons surrounded by myelin (left) and regeneration of axons at the distal nerve ending with clumps of nerve sprouts (right)
Fig. 4: Silver stain (for axons - black) and Luxol-Fast-Blue (for myelin – blue) – Proximal nerve end (left) and the distal nerve ending showing myelin sheath formation (right)
Conclusions
The ideal nerve repair should be tension free and have adequate vascularity. These points can be achieved with the FTF. Our pilot study is the first animal study of this technique, with functional and histopathological studies showing that the FTF has similar results to the FNG, with the added benefit of avoiding donor site morbidity, significantly improving the management of nerve gaps.
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