Medial Triceps as a Preferential Nerve Donor in Axillary Motor Nerve Transfer for Isolated and Brachial Plexus-Associated Axillary Nerve Palsy
Emily Krauss, BSc MSc MD, University of British Columbia, Victoria, BC, Canada, Elspeth J R Hill, MD PhD MRes, Washington University School of Medicine, St Louis, MO, Shelley S. Noland, MD, Mayo Clinic, Phoenix, AZ, Nirbhay S Jain, MD, University of California, Los Angeles, Los Angeles, CA, Lorna C Kahn, BSPT CHT, Washington University, St. Louis, MO and Susan E Mackinnon, MD, Washington University School of Medicine, Saint Louis, MO
Introduction
Axillary nerve transfer was originally described using the branch to long head of triceps to reconstruct axillary nerve function. Since 2007, our institution has preferred using medial triceps branch in both brachial plexus and isolated axillary nerve palsies. This donor provides longer length for transfer, two distal branches, and larger cross-sectional area, hypothetically providing more axonal fibers 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 those 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
Eighty-two (82) patients were treated with medial triceps to axillary nerve transfer. Seventeen (17) patients were excluded for insufficient follow-up (< 3 months). Median time to surgical intervention was 6 .5 months (IQR 4.7-9.4 months). Median DASH scores were 55.1 (IQR 35.5, 69.7, N=48) preoperatively and 31.9 (IQR 15.1, 53.1, N=56) at final follow-up. 4 patients had no re-innervation in deltoid muscle after transfer. MRC grade 3 or greater was achieved in 63.1% of patients, 29.2% achieved near perfect results (MRC ≥ 4) and 3 (4.6%) had an MRC of 5. No patients achieved normal function. Isolated axillary nerve reconstruction had significantly greater deltoid recovery compared to transfers performed for brachial plexus -associated axillary nerve palsy (p=0.002). 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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