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Which Nerve to Use? Comparison Between Donor Nerves to Motorize the Free Functional Gracilis Muscle Transfer for Elbow Flexion in Traumatic Brachial Plexus Injuries

Introduction: Elbow flexion deficit is a frequent problem in traumatic brachial plexus injuries and reestablishment of this function is the primary treatment goal. When management is delayed or the initial acute approach fails, free functional transfer of the gracilis muscle for elbow flexion is the treatment of choice: the authors seek to determine which donor nerve (spinal accessory, intercostal, median, or ulnar) results in better elbow flexion after microsurgical reconstruction. Methods: Retrospective analysis of patients with traumatic brachial plexus injuries who underwent functional free gracilis muscle flap for elbow flexion between February 2003 and October 2014 was carried out. Postoperative function of the gracilis functional flap was recorded and patients were divided into 4 groups according to donor nerve: spinal accessory nerve (SAN), intercostal nerves (ICN), motor fascicles of the median (MED), and ulnar nerve (ULNAR). Cases in which a primary neurorrhaphy was not possible were further subdivided into 2 groups: SAN with graft interposition (SAN graft) and ICN with graft interposition (ICN graft). The final elbow flexion strength was evaluated by the British Medical Research Council (BMRC) scale and time in months when the authors first observed M3 muscle power was also of note. Results: Fifty-nine patients met inclusion criteria for this retrospective study. Two cases were excluded due to flap loss (3%) and 3 were lost to follow up (5%). Of the 54 patients enrolled, 53 were males (98.2%) with a mean age of 29 years. The mean follow-up period was 28 months. Thirty-four cases obtained muscle strength of ≥ M3 (62.9%), 6 M0 (11.1%), 4 M1 (7.5%), 10 M2 (18.5%), 13 M3 (24%), and 21 M4 (38.9%). The mean interval to first recorded M3 muscular strength was 16 months. Patients stratified by donor nerve achieving ≥ M3 had the following distribution: SAN 83.3% (15/18), SAN graft 50% (2/4), ICN 50% (2/4), ICN graft 33.3% (1/3), MED 40% (2/5), and ULNAR 60% (12/20). No statistical difference for final muscle strength was found between donor nerve groups. SAN transfer with graft interposition took longer to reach muscle strength of M3 or greater (P < .05). Conclusion: Free functional gracilis muscle flap for traumatic brachial plexus injuries is a viable option for elbow flexion recovery. Comparison between 4 different nerve transfers—SAN, ICN, MED, and ULNAR—did not clearly indicate a better alternative over the others.