If you see a patient with an injured nerve late, or decide not to repair it at the time of the injury, the only way to repair it is by trial section and resuture. If you cannot refer him, you may have to do this yourself.
To begin with there is a blood clot between the fascicles of a recently cut nerve, as in A, Fig. 55-10. This soon becomes organized and invaded by fibrous tissue to form a rounded neuroma (B). You will have to cut this back in a succession of s mall slices until you reach healthy nerve (C). Sometimes a nerve is incompletely divided and although its ends are joined it is deformed by bulbous neuromas (D). These too have to be cut back until you reach healthy nerve.
The best time for secondary repair is 3 weeks after the patient’s initial injury. You may find that, when you have excised the retracted fibrosed cut ends of his nerve, it has to bridge quite a gap. Nerves are not very elastic, so this can be difficult. An expert may be able to bridge the gap with a graft. Your best hope is to explore the nerve through an enormous long incision, so that you can mobilize enough nerve to make it stretch the gap. For example, you may have to explore the ulnar nerve from the wrist to the elbow and down into the hand.
Another difficulty is finding the cut ends of the nerve deep in the scar of the wound. Look for them proximally and distally, and then follow both ends into the fibrous tissue of the wound. Be careful not to cut theta as you look for them. Use blunt dissection, where you can. If you have to use a scalpel, cut in the length of the nerve, not across it.