Surgical nerve repair involves exploration of the injured nerve and removal of injured tissue or scar from the nerve endings. After that, a nerve can be directly reconnected if there is enough length on the ends to allow for a good quality repair without tension. Repairs are performed with the assistance of an operating microscope to allow for the best alignment of the fiber bundles, called fascicles, inside of the injured nerve. In some cases when a larger amount of tissue has to be removed from the nerve endings, there is too large a gap to allow for direct repair. In those cases, a non-essential nerve will be sacrificed from a separate location on the body (usually from the leg or upper arm) and used to bridge the nerve gap. This procedure is known as nerve grafting. Other approaches for repair such as a conduit, an artificial tube connecting the nerve endings, may be used in particular circumstances when grafts are not possible. Nerve graft substitutes, derived from donated nerve tissues, are also appropriate instead of nerve grafting for some patients.