The effects of lengthening on nerves.

Use of external fixators in limb lengthening and skin expanders in plastic surgery are well-known operative techniques. In some cases neurologic complications arise due to distraction which is either excessive or too fast. What happens to the nerve in these cases has not yet been thoroughly investigated. We therefore conducted an experiment on the sciatic nerve of rats. In one group of animals the nerve was studied after lengthening the femur, and in the other group after lengthening the nerve itself with a skin expander. Electrophysiologic and histologic studies (optic microscopy and axon teasing) were used to examine the effects of tension on the sciatic nerve. The results suggest that if distraction is performed gradually, the nerve does not undergo any electrophysiologic functional changes. It does, however, undergo some morphologic changes, such as a decrease in both the areas of the axons and the myelin sheaths, an increase in the distances between the nodes, and proliferation of Schwann cells.