American Society for Peripheral Nerve

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Outcome Analysis of Medial Triceps Motor Nerve Transfer to Axillary Nerve in Isolated and Brachial Plexus-associated Axillary Nerve Palsy
Emily M. Krauss, MD, MSc1; Shelley Suzanne Noland, MD2; Lorna Kahn, PT CHT3; Susan E. Mackinnon, MD1
1Plastic and Reconstructive Surgery, Washington University, St. Louis, MO, 2Mayo Clinic Arizona, Phoenix, AZ, 3The Rehabilitation Institute of St Louis, Saint Louis, MO

Introduction: Originally described using the branch to long head of triceps1, our institution has performed the triceps to axillary nerve transfer using the medial triceps branch since 2007 to reconstruct axillary nerve function in both brachial plexus and isolated axillary nerve palsies. The choice of donor was based on its longer length for transfer, two distal branches, and larger cross-sectional area, leading to the hypothesis of more neural input for transfer. This is the first large series assessing strength and functional outcomes from medial triceps to axillary nerve transfer from our center.

Materials & Methods: A retrospective chart review of patients treated with a medial triceps to axillary nerve transfer for complete axillary nerve palsy was performed. Patient demographics, injury mechanism, associated injuries, electrodiagnostic studies (EMG) and time to surgery were analyzed. Pre-and post-operative function was assessed using the modified MRC muscle strength grading and the DASH questionnaire. Subgroup analysis for brachial plexus and isolated axillary nerve injuries was performed using the Mann-Whitney U test.

Results: Fifty-eight (58) patients were treated with medial triceps to axillary nerve transfer. Sixteen (16) patients were excluded for insufficient follow-up (< 5 months). Median time to surgical intervention was 6 months (IQR 4-8). Median pre- and post-operative DASH scores were 57.73 (N=28, IQR 22.2-70.9) and 28.3 at final follow-up (N=27, range 9.2-60.0). Only 4 patients had no re-innervation in deltoid muscle after transfer. MRC grade 3 or greater was achieved in 69.0% of patients, 28.6% achieved near perfect results (MRC ≥ 4). No patients achieved normal function. Isolated Axillary Nerve Palsy had significantly greater deltoid recovery compared to transfer performed for brachial plexus -associated axillary nerve palsy (3+ vs 3, p=0.048). There was no significant difference in postoperative deltoid strength or DASH scores between patients with axillary nerve transfer versus axillary nerve transfer plus suprascapular nerve reconstruction.

Conclusions: Medial triceps nerve branch is a strong donor for triceps to axillary nerve transfer; however, injury factors may limit the motor recovery in this complex patient population, particularly in brachial plexus-associated axillary nerve palsy.

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