American Society for Peripheral Nerve

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Axon Counts Yield Multiple Options for Triceps to Axillary Nerve Transfer
M. Michael Khair, MD1, Joseph J. Schreiber, MD1, Lauren Rosenblatt, BA1, David J. Byun, BA1, Steve K. Lee, MD2 and Scott W. Wolfe, MD2
1Orthopaedic Surgery, Hospital for Special Surgery, New York, NY, 2Hand and Upper Extremity Surgery, Hospital for Special Surgery, New York, NY

Introduction: Triceps to axillary nerve transfer is an established procedure for restoration of deltoid function following denervation. We sought to evaluate the relative axonal match between potential donor and recipient nerves so that maximal reinnervation potential may be reached with the least chance of donor site morbidity. This information can help peripheral nerve surgeons plan and perform nerve transfers to restore both external rotation and abduction with the highest potential for success. Methods: Following a posterior humeral dissection of both the axillary and radial nerve in 10 fresh frozen cadaveric specimens, a gross description of the branching patterns of the nerves was performed. The posterior, anterior, sensory, and teres minor branches were identified, mapped and measured from their exit point in the quadrilateral space. Similarly, the multiple branches to the long, medial, and lateral heads of the triceps were identified, and the arborization and appearance of the nerves was documented. Biopsies of each branch were taken, pinned to anatomic length, and processed for histological analysis. Axon counts were performed on all samples. Results: The average number of axons in the main axillary trunk was 7101 (range 6580-7622) axons. The average number in the anterior, posterior and teres minor branches was 4149 (range 4067-4231), 886 (range 653-1120), and 830 (range 467-1193) axons respectively. The average number of branches to the long head of the triceps was 1.75 (range 1-3). The average number of axons present in each branch was 880 (range 614-1022) axons. The main branch to the long head of the triceps contained on average 1629 axons. The average number of branches to the medial head was 1.5 (range 1-2). The average number of axons present in these branches was 2790 (range 1945-3636) axons. The average number of branches to the lateral head of the triceps was 1.5 (range 1-3). In these branches the average number of axons totaled 315 (range 229-404) axons. The main branch to the lateral head contained on average 1373 axons. Conclusion: It is feasible to transfer multiple braches of the radial nerve supplying the long, medial and lateral head of the triceps to all branches of the axillary nerve in an attempt to re-innervate the deltoid and teres minor. The average axon counts of the different possible transfer combinations will help peripheral nerve surgeon plan their transfers in an attempt to maximize both abduction and external rotation while minimizing the morbidity of transfers.


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