Tiam Mana Saffari

237 GENERAL DISCUSSION 11 validated to provide vascularity to the sciatic nerve area. This flap was raised from the abdomen, rotated and subcutaneously tunneled towards the sciatic nerve. The pedicled SIEF flap was wrapped around the nerve graft, covering the entire nerve and both reconstruction sites. This technique was proven reliable, demonstrated a total success rate of flap viability without necrosis at 12 and 16 weeks, did not require microsurgical repair of blood vessels and therefore decreased the risk of complications. This method was used in the subsequent studies of this thesis to evaluate the role of vascularization on nerve allografts. To understand the effect of the SIEF f lap on nerve grafts and the mechanisms of vascularization, I aimed to evaluate the amount of (neo)angiogenesis. Previous studies have focused on immunohistochemical staining, which lacks the three- dimensional (3D) interconnectivity of the vasculature in serial histological sections 14,15 . Therefore, conventional photography and microcomputed tomography (micro CT) were investigated to objectively quantify vascular surface area and vascular volume, respectively, as measurements of angiogenesis in the nerve. These novel techniques were validated in Chapter 4 and objectively provided detailed two-dimensional (2D) and 3D information. The ultimate goal is to describe neoangiogenesis -the formation of new blood vessels- 16 in nerve. This would allow us to evaluate and compare neoangiogenic effects of various treatments. However, the distinction between pre- existing and newly formed vessels is technically difficult. The decellularized nerve allograft is per definition acellular and undergoes revascularization in vivo after implementation. Measuring angiogenesis in decellularized nerve allografts over time gives an estimation of the newly formed vessels and could be compared to allografts augmented with a adipofascial flap to evaluate the effect of vascularization. By combining the described techniques in Chapters 3 and 4, Chapter 5 investigated how augmentation of nerve allografts with angiogenesis affects revascularization patterns over time. The findings provided evidence for answering two important questions. First, it was shown that augmentation of nerve allografts with angiogenesis increases revascularization. While this finding does not come unexpected, it strongly supports the vascular contribution of the surrounding bed. Revascularization of nerve is postulated to occur from (i) extraneural vascular contribution from surrounding beds (centripetal revascularization) and (ii) longitudinal bidirectional inosculation from the proximal and distal ends of the graft 17-19 . One may argue that the muscular