上中下三干后股对指总伸肌及肱三头肌长头交叉支配的电生理研究

Electrophysiological analysis of the dominance innervation of extensor digitorum communis muscle and long head of triceps brachii muscle at the level of posterior division of brachial plexus

目的通过术中电生理检测，在臂丛神经中找到指总伸肌支配神经的相对集中区，为神经移位重建伸指功能新术式的设计提供理论依据。方法2008年2月-2009年10月，17例臂丛神经撕脱伤行健侧C7神经根移位术。应用Keypoint型肌电图仪，术中分别对上、中、下三干后股进行电刺激，在指总伸肌及肱三头肌长头记录复合肌肉动作电位（compound muscle action potential，CMAP）。结果指总伸肌记录到的CMAP最大波幅有76．5％（13／17）为电刺激下干后股，17．6％（3／17）为电刺激中干后股，5．9％（1／17）为电刺激上干后股。电刺激上、中、下三干后股在指总伸肌记录到的CMAP波幅平均值分别为：0．75±1．16mV，1．64±1．54mV，5．32±4．58mV。在肱三头肌长头记录到的最大CMAP波幅有53％（9／17）为电刺激中干后股，47％（8／17）为电刺激下干后股。电刺激中干及下干后股在肱三头肌长头记录到的CMAP平均波幅分别为4．57±3．84mV，5．98±8．43mV。结论支配指总伸肌的神经纤维来自下千后股比C7后股的多，而下干后股亦是肱三头肌长头的主要支配神经。

Objective To identify the concentrated section of fascicles at the level brachial plexus that innervate the extensor digitorum communis muscle of posterior division ot using intraoperative electrophysiological testing and provide the theoretical basis for the modified procedure of nerve transfer to restore the function of finger extension. Methods From Feb 2008 to Oct 2009, 17 patients including 14 males and 3 females suffered brachial plexus avulsion injury who underwent the contralateral C7 nerve root transfer were involved in this study. The average age was 22 years, with a range of 5 to 27 years. The entire brachial plexus of normal side was exposed. The posterior divisions of upper, middle and lower trunk were identified through the supraclavicle incision. The compound muscle action potential （CMAP） was recorded in the long head of triceps of brachii and extensor digitorum communis muscle using electrophysiological device as the posterior divisions of upper, middle and lower trunk were electrical stimulated respectively. Results 76.5% （13/17）of the maximal amplitude of CMAP recorded in extensor digitorum communis muscle was induced by electrical stimulating the posterior division of lower trunk, 17.6%（3/17） by electrical stimulating the posterior division of middle trunk and 5.9% （1/17） by electrical stimulating the posterior division of upper trunk. The average amplitude of CMAP was 0.75 ± 1.16, 1.64 ± 1.54 and 5.32 ±4.58 respectively by electrical stimulating the posterior division of upper, middle and lower trunk. 53%（9/17） of the maximal amplitude of CMAP recorded in the long head of triceps of brachii muscle was induced by electrical stimulating the posterior division of middle trunk, 47%（8/17） by electrical stimulating the posterior division of lower trunk. The average amplitude of CMAP was 4.57 ±3.84 mV, 5.98 ±8.43 mV respectively by electrical stimulating the posterior division of middle and lower trunk. Conclusion The number of nerve fibers innervating the extensor digitorum communis muscle originated from the posterior division of lower trunk is more than that of C7 nerve root. The posterior division of lower trunk also innervate the long head of triceps ofbrachii muscle.