Snug tubular enclosures reduce extrafascicular axonal escape at peripheral nerve repair sites

A method of fascicular nerve repair utilizing silicone rubber tubes has been developed and tested in the dog whose nerves, like those of man, have a thick epineurial sheath. The closely fitting tubes provide a noncompressive enclosure which minimizes axonal escape and facilitates axon regeneration in at least two ways: First, they provide an impermeable conduit for endoneurial fluid whose constituents create an environment favoring the regeneration of axons and Schwann cells. Second, the biocompatible tube induces rapid development of a highly organized capsule which isolates the repair site, prevents adhesions, and strengthens the discontinuity. Enclosure of coapted fascicles also improves alignment of endoneurial components while providing space for the resolution of edema. The inert, noncompressive enclosures appear to minimize unregulated axonal growth at the site of injury by providing a qualitatively distinct environment from that in loose or open tubes.