Tiam Mana Saffari

15 GENERAL INTRODUCTION 1 Peripheral nerve recovery elicits a fine balance of axonal sprouting and scar formation, following the principles of wound healing. In severe injuries, fibroblasts secrete large amounts of collagen, resulting in the formation of dense scarring. Nerve scarring, or fibrosis, can alter perineural microvasculature and impair nerve regeneration 19 . CURRENT APPROACHES FOR NERVE RECONSTRUCTION The prevailing wisdom regarding the surgical management of the peripheral nerve gap has changed over the past century. The current surgical intervention for peripheral nerve reconstruction consists of microsurgical epineural suture of aligned proximal and distal stumps, performed when a tension-free coaptation can be achieved 20,21 . Tension into the nerve cable is deleterious to nerve regeneration and has been demonstrated to result in scar formation in the 1970s by Millesi and colleagues 22 . Following severe nerve trauma with excessive tension between nerve ends, primary (end-to-end) repair is therefore is not possible, and nerve interposition is needed to reconstruct the nerve defect. Although nerve interposition was thought to yield inferior outcomes prior to the 1970s, the novel insights introduced interfascicular tension-free nerve grafting with fascicles matching in size, as a new option for repair of peripheral nerves 23 . The speed at which nerves regenerate through the graft to reach the motor endplate is time dependent, which can significantly affect motor outcome and restoration of function 24,25 . Currently, there are several options for nerve reconstruction, each associated with its own advantages and disadvantages. Nerve autograft For the reconstruction of segmental nerve defects, the gold standard remains the use of an autologous nerve graft (autograft): the use of the patient’s healthy nerve, as donor, to bridge the nerve gap 22 . The autograft provides a scaffold for nerve regeneration, while including preserved nervous architecture and biology, e.g. viable Schwann cells and vasculature. Furthermore, the autograft is non-immunogenic and the preferred option for reconstruction of motor and mixed nerves 26 . The disadvantages include the associated donor site morbidity and limited availability 27 . The sural nerve, which is purely sensory and easily harvested, is the most common nerve graft donor and provides a graft length up to 40 cm in adults (Figure 3). Donor nerve selection is based on size match to the injured nerve, ease of harvest and minimizing postoperative