Double-Nerve Transfer to the Axillary Nerve in Traumatic Upper Trunk Brachial Plexus Injuries Using an Axillary Approach: Anatomical Description and Preliminary Case Series.

Background: Restoration of shoulder external rotation remains challenging in patients with C5/C6 brachial plexus injuries (BPI).

Objective: To describe a double-nerve transfer to the axillary nerve (AN), targeting both its anterior and posterior motor branches, through an axillary route.

Methods: A total of 10 fresh-frozen cadaveric brachial plexuses were dissected. Using an axillary approach, the infraclavicular brachial plexus terminal branches were exposed, including the axillary, ulnar, and radial nerves. Under microscopic magnification, the triceps long head motor branch (TLHMB), anteromedial fascicles of the ulnar nerve (UF), the anterior motor branch of the axillary nerve (AAMB), and the teres minor motor branch (TMMB) were dissected and transected to simulate 2 nerve transfers, THLMB-AAMB and UF-TMMB. Several anatomical criteria were assessed, including the overlaps between fascicles when placed side-by-side. Six patients with C5/C6 BPI were then operated on using this technique.

Results: TLHMB-AAMB and UF-TMMB transfers could be simulated in all specimens, with mean overlaps of 37.1 mm and 6.5 mm, respectively. After a mean follow-up of 23 mo, all patients had recovered grade-3 strength or more in the deltoid and teres minor muscles. Mean active shoulder flexion, abduction, and external rotation with the arm 90° abducted were of 128°, 117°, and 51°, respectively. No postoperative motor deficit was found in the UF territory.

Conclusion: A double-nerve transfer, based on radial and ulnar fascicles, appears to be an adequate option to reanimate both motor branches of the AN, providing satisfactory shoulder active elevations and external rotation in C5/C6 BPI patients.