Use of tubes in peripheral nerve repair.

The use of tubes as an alternative to primary nerve suture in fresh nerve transections has been introduced as a biologic approach to nerve injuries, creating optimal conditions for axonal regeneration over a short empty space intentionally created between the proximal and distal nerve ends. The idea may seem controversial and has been criticized using the arguments that silicone in itself may create problems like inflammation and the tube may compress the nerve ends. With the use of appropriately sized tubes for bridging a maximum 5-mm gap in human median and ulnar nerves, the authors have found the technique to be useful and persistent at follow-up examinations for up to 4 to 5 years. In addition, from the intellectual point of view, the principle illustrates the concept by which emphasis is placed on the intrinsic healing capacities of the nerve rather than on the technical skill of the surgeon. The thin mesothelial lining found around the silicone tube lacks primary inflammatory signs at follow-up after 1 year, and no signs of compression are seen. It may be an advantage because it allows sliding of the repair site against the surrounding tissues. Tubes made of bioresorbable material may seem ideal, but they may introduce new problems associated with the resorption process in terms of a substantial unrestricted macrophage invasion, fibrosis, and disorganized axonal growth. For an extended nerve defect, the use of autologous nerve grafts is still the gold standard, because no tubular conduit or other conduit has so far proved equal to autologous nerve grafts, at least not for reconstruction of human median and ulnar nerve trunks. Alternatives other than tubes are currently being developed and investigated. For the future, the use of tubes for repair and reconstruction of nerves may have interesting potentials, because such a structure allows several types of tissue engineering. Various matrices containing, for instance, appropriate cells, factors, or other stimulating agents can be introduced in the tube lumen and can also be incorporated in a slow-release form in the walls of the tube and manipulated. Cultured Schwann cells or other cellular components, with or without manipulated production machinery, are probably the cells of choice for introduction in the tubes. Tubes may thus prove to be interesting alternatives to conventional repair techniques for primary repair of nerves and for reconstruction of segmental defects and for neuroma treatment in the future.