Is it necessary to use the entire root as a donor when transferring contralateral C7 nerve to repair median nerve?

Abstract

If a partial contralateral C₇ nerve is transferred to a recipient injured nerve, results are not satisfactory. However, if an entire contralateral C₇ nerve is used to repair two nerves, both recipient nerves show good recovery. These findings seem contradictory, as the above two methods use the same donor nerve, only the cutting method of the contralateral C₇ nerve is different. To verify whether this can actually result in different repair effects, we divided rats with right total brachial plexus injury into three groups. In the entire root group, the entire contralateral C₇ root was transected and transferred to the median nerve of the affected limb. In the posterior division group, only the posterior division of the contralateral C₇ root was transected and transferred to the median nerve. In the entire root + posterior division group, the entire contralateral C₇ root was transected but only the posterior division was transferred to the median nerve. After neurectomy, the median nerve was repaired on the affected side in the three groups. At 8, 12, and 16 weeks postoperatively, electrophysiological examination showed that maximum amplitude, latency, muscle tetanic contraction force, and muscle fiber cross-sectional area of the flexor digitorum superficialis muscle were significantly better in the entire root and entire root + posterior division groups than in the posterior division group. No significant difference was found between the entire root and entire root + posterior division groups. Counts of myelinated axons in the median nerve were greater in the entire root group than in the entire root + posterior division group, which were greater than the posterior division group. We conclude that for the same recipient nerve, harvesting of the entire contralateral C₇ root achieved significantly better recovery than partial harvesting, even if only part of the entire root was used for transfer. This result indicates that the entire root should be used as a donor when transferring contralateral C₇ nerve.

Keywords: animal experiment; avulsion injury; brachial plexus injury; contralateral C7 transfer; entire root; median nerve; nerve regeneration; nerve root; neural regeneration; partial root; peripheral nerve injury; ulnar nerve.

Figure 1

C₅–T₁ nerve roots (arrows) on the right side were exposed and blocked by 2% lidocaine and then transected at the level of the intervertebral foramen to simulate total brachial plexus injury.

Figure 2

Transfer of the entire root, posterior division and entire root + posterior division. (A) The entire root of contralateral C₇ (cC₇) nerve (↓) was transected at the trunk-to-division level and coapted with the ulnar nerve (*) on the affected side, with no tension, by 11-0 microsutures. (B) The anterior division (→) and posterior division (▴) of the cC7 nerve were separated at the division level and only the posterior division (▴) was transected and coapted with the ulnar nerve (*) on the affected side, with no tension, by 11-0 microsutures. (C) Both the anterior (→) and posterior (▴) division of the cC7 nerve was transected at the division level, while only the posterior division (▴) was coapted with ulnar nerve (*) on the affected side, with no tension, by 11-0 microsutures. The anterior division was transferred to the pectoralis major bridged by the medial antebrachial cutaneous nerve (#) on the affected side.

Figure 3

Morphology of the FDS and neuromorphology of the median nerve in the affected limb. The upper panels show the muscle morphology of the FDS, stained with hematoxylin and eosin, of the three groups at 16 weeks post-operation at 200× magnification. The bottom panels show the neuromorphology of the median nerve, stained with 5% toluidine blue, of the three groups at 400× magnification at 16 weeks post-operation. The muscle fiber cross-sectional area of the FDS of the entire root group and the entire root + posterior division group was larger than that of the posterior division group and significantly greater axon numbers, with better morphology of the myelinated fibers can be seen in the entire root group. In the entire root group the entire contralateral C₇ root was transected and transferred to the median nerve of the affected limb. In the posterior division group, only the posterior division of the contralateral C₇ root was transected and transferred to the median nerve. In the entire root + posterior division group, the entire contralateral C₇ root was transected but only the posterior division was transferred to the median nerve. FDS: Flexor digitorum superficialis.