Tubulation for peripheral nerve gap: Its history and possibility

A large gap in peripheral nerve will not allow effective regeneration unless a grafting conduit is used to bridge the defect. Conventionally, nerve tissue has been used as such a conduit in nerve reconstruction; however, results from techniques using these grafts are often unsatisfactory. A number of recent investigations have indicated that nerve fibers will regenerate through a non-neural tube. The purpose of this review is: 1) to provide an overview of the various tubulation techniques previously reported for peripheral nerve gap repair; 2) to investigate new possibilities for enhancing the regenerative capacity of nerves following these tubulation techniques by drawing from technical innovations in microsurgery and recent progress in immunology and neurobiology. The interposed graft thus may perform a more positive role, not merely as a pathway for deregenerating axons, but as a source for neuronotrophic factors and neurite-promoting factors, which would nurture and guide the neurons and axons. Such modifications in graft materials may lead to clinical applications of tubulation of nerve defects that would result in an improvement in clinical results.