Tiam Mana Saffari

146 CHAPTER 7 DISCUSSION Interest in the role of vascularity in nerve regeneration has been longstanding 35 . In the past, experimental animal models have investigated the effects of vascular growth factors such as vascular endothelial growth factor (VEGF) 36 , or sought to measure the effect of microsurgical repair of nerve graft with vascular pedicles (e.g. VNG) on nerve regeneration 20,22,23,37,38 . VEGF contributes to angiogenesis via several mechanisms and has also been suggested to inf luence nerve regeneration 36,39 by stimulating outgrowth of Schwann cells, the original facilitators of nerve regeneration 40,41 . These cited studies have reported conflicting results and are difficult to compare. One previous study evaluated functional recovery in rats and found improved sciatic functional index in VNGs at eight and 12 weeks 20 . This is in line with our study, which showed increased muscle force when allografts were wrapped within an adipofascial flap when compared to allografts alone at 12 weeks. Because of its reproducibility, ITF has become a widely used standardized technique to assess mechanical function and the contractile properties of muscles 42,43 . This study and others have demonstrated that ITF is a reliable technique in determining the degree of functional recovery of a reinnervated muscle as a direct measure of reinnervation 5,44-46 . Electrophysiological outcomes trended to be superior in the allograft wrapped within the SIEF, compared to nerve allograft alone. As CMAP is greatly affected by factors such as changes in temperature and electrode location, there is greater variability than ITF data 31 . Although others have reported VNGs to have significantly higher nerve conduction velocity than non-VNGs 20 , this could not be corroborated in our study. Denervated tibial muscles were characterized by differences in muscle mass and ultrasoundmeasurements. Serial cross-sectional muscle scans in vivo provided insights into muscle atrophy and reinnervation over time, but was not sufficiently sensitive enough to determine small differences between groups in our rat model. Although our results did not show a significant difference in muscle mass between allograft and SIEF group, wrapping with the SIEF flap provided a significant, large improvement inmuscle force at 12 weeks. Muscle mass includes enlarging but non-contractile muscle fibers, resulting in possible indistinguishable differences in innervated and non-innervated muscles 32,47,48 . It is easy to interpret, however, doubtful to be useful as an evaluation