EXPERIMENTAL STUDY ON NERVE ELONGATION

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The purpose of this study is to know where the sciatic nerve is elongated macroscopically and histologically when the rabbit femur is lenghthened gradually by an external fixator.An external fixator was newlly manufactured for a rabbit femur. A pin for fixation was selected among several industrial pins, 1.6 mm Kirschner wire and M-300 cortical tappered half screw (Orthofix). The first two were not usable as the femur was brokened or pin was bend. So, M-300 cortical tappered half screw (Orthofix) was used for the fixator's pin.When the femur wsa elongated as a rate of 1mm per day for 20 days, the femur was elongated from 15.9 to 18.9 mm, that is 16.5 to 18.5% with an average of 17.2% of the healthy side. During this elongation, there were no findings of sciatic nerve palsy.When the sciatic nerve was marked 1mm cach by 6-0 stenless steel wire, the nerve was elongated 11.6 to 14.6 mm with an average of 12.9 mm, that is 11.0 to 14.6% with an average of 12.7% of the helthy side. The sciatic nerve was elongated along the whole course of the nerve, although the proximal and distal part were more elongated than the central part with no statistical differences.After teasing of the nerve, no myelinated nerve fibers showed Wallerian degeneration. The Ranvier's node was normal in structure and length and the internodal distance was elongated. This means nerve was elongated internadally, not at the Ranvier's node during limb lengthening.