• Li Chen, Lei Xu, Yudong Gu, Jianguang Xu, Wendong Xu, Jiuzhou Lu, and Yi Zhu.
• Department of Hand Surgery, Huashan Hospital, Fudan University, Shanghai, 200040, P.R. China.
• Zhongguo Xiu Fu Chong Jian Wai Ke Za Zhi. 2008 Sep 1;22(9):1036-9.

ObjectiveTo analysis the electrophysiological dominance weight of the triceps brachii muscle/extensor digitorum communis muscle innervated by brachial plexus and to conclude its effect on the ipsilateral C7 transfer so as to offer electrophysiological data for the safety and indication of ipsilateral C7 transfer.MethodsFrom August 2007 to October 2007, 15 patients with complete brachial plexus nerve root avulsion received contralateral C7 transfer. There were 13 males and 2 females aged 18-49 years (28 years on average). Injury was caused by falling in 1 case, by crush in 2 cases and by traffic accident in 12 cases, involving left side in 8 cases and right side in 7 cases. The upper, middle and lower trunk of the brachial plexus were stimulated respectively, the compound muscle action potential (CMAP) at the triceps brachii muscle/extensor digitorum communis muscle was recorded, and then the electrophysiological dominance weight of the triceps brachii muscle/extensor digitorum communis muscle innervated by brachial plexus was confirmed according to the comparison of the amplitude percentage of the CMAP by three trunks. The muscle strength of triceps brachii muscle/extensor digitorum communis muscle was evaluated and the electromyogram was taken 6 months after operation.ResultsAll patients were followed up for 6 months. Concerning the electrophysiological dominance weight, the triceps brachii muscle was mainly innervated by upper-middle trunk in 3 cases (20%), by middle-lower trunk in 3 cases (20%), by whole trunk in 7 cases (47%) and by middle trunk in 2 cases (13%). While the extensor digitorum communis muscle was mainly innervated by middle-lower trunk in 3 cases (20%), by whole trunk in 10 cases (67%) and by lower trunk in 2 cases (13%). Concerning the triceps brachii muscle, 2 patients got the muscle strength of 4 grade with recruitment simple phase at 1 month after operation and returned to normal at 3 month after operation, while 13 patients got the muscle strength of 5 grade with recruitment simple or mixed phase at 1 month after operation. Concerning the extensor digitorum communis muscle, the muscle strength and the recruitment phase of all 15 patients recovered to normal at 1 month after operation.ConclusionTo patients with various kinds of electrophysiological dominance weight, the cutting of C7 does not substantially damage the triceps brachii muscle or extensor digitorum communis muscle, indicating that the ipsilateral C7 transfer is safe and feasible. However, it should be applied prudently for the patients with high dominance weight since it may result in the short-term decrease of triceps brachii muscle strength.

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