Experimental study of direct transfer of contralateral C7 to the lower trunk for the treatment of total root avulsions of the brachial plexus

Objective To investigate the feasibility and effectiveness of contralateral C7 transfer to the lower trunk for total root avulsion of the brachial plexus. Methods Thirty-six female SD rats were randomly divided into three groups. In group A, contralateral C7 nerve root was transferred to the lower trunk directly. Group B was the normal control group, while group C had total root avulsion without repair. Twenty-four weeks after the surgery, electrophysiological examination, neuromorphometry, muscle cross-sectional area, muscle wet weight and motor endplate detection were carried out to evaluate the outcomes of each group. Results Nerve fiber diameter and N ratio in the ulnar nerve and median nerve were not significantly different between group A and group B (P>0.05). Total myelinated fiber counts in the ulnar nerve were not different between group A and group B (P>0.05), while there were significantly fewer myelinated fibers in the median nerve of group A than in the median nerve of group B (P 0.05). In flexor digitorum superficialis (FDS), group A had lower CMAP amplitude and longer latency than group B (P 0.05) but greater than group C (P 0.05) but heavier than group C (P>0.05). Muscle cross-sectional areas of both FCU and FDS in group A were smaller than group B (P<0.05) but larger than group C (P<0.05). Conclusion Direct contralateral C7 transfer to the lower trunk is feasible. Its effectiveness is shown by recovery in electrophysiology, neuromorphometry, and muscle histology. Key words: Brachial plexus; Nerve transfer; Contralateral C7; Lower trunk