EXPERIMENTAL STUDY ON NERVE ELONGATION

本研究的目的是了解当兔股骨被外固定器逐渐延长时，坐骨神经在大体和组织学上被延长的部位。从多枚工业钉、1.6 mm克氏针和M-300皮质攻丝半螺钉(Orthofix)中选择一枚用于固定。前两个由于股骨折断或钉弯曲而无法使用。采用M-300皮质自攻半螺丝钉(Orthofix)固定股骨，以每天1 mm的速度延长20d，股骨平均延长15.9~18.9 mm，平均为健侧的17.2%。当用6-0号钢丝固定坐骨神经1 mm时，神经延长11.6~14.6 mm，平均12.9 mm，占健侧的11.0~14.6%，平均12.7%。坐骨神经全程延长，但近端和远端较中央部延长，无统计学差异；神经牵拉后无有髓神经纤维瓦勒氏变性。兰氏结节结构和长度正常，节间距离延长。这意味着在肢体延长的过程中，神经是在内侧延长的，而不是在兰维尔结处。

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.