Rectus Abdominis Motor Nerves as Donor Option for Free Functional Muscle Transfer: A Cadaver Study and Case Series

Background: Current management of brachial plexus injuries includes nerve grafts and nerve transfers. However, in cases of late presentation or pan plexus injuries, free functional muscle transfers are an option to restore function. The purpose of our study was to describe and evaluate the rectus abdominis motor nerves histomorphologically and functionally as a donor nerve option for free functional muscle transfer for the reconstruction of brachial plexus injuries. Methods: High intercostal, rectus abdominis, thoracodorsal, and medial pectoral nerves were harvested for histomorphometric analysis from 4 cadavers from levels T3-8. A retrospective chart review was performed of all free functional muscle transfers from 2001 to 2014 by a single surgeon. Results: Rectus abdominis nerve branches provide a significant quantity of motor axons compared with high intercostal nerves and are comparable to the anterior branch of the thoracodorsal nerve and medial pectoral nerve branches. Clinically, the average recovery of elbow flexion was comparable to conventional donors for 2-stage muscle transfer. Conclusion: Rectus abdominis motor nerves have similar nerve counts to thoracodorsal, medial pectoral nerves, and significantly more than high intercostal nerves alone. The use of rectus abdominis motor nerve branches allows restoration of elbow flexion comparable to other standard donors. In cases where multiple high intercostal nerves are not available as donors (rib fractures, phrenic nerve injury), rectus abdominis nerves provide a potential option for motor reconstruction without adversely affecting respiration.