Distal Branching Patterns of Axillary Nerve; Implications for Axillary to Radial Nerve Transfer
Peter Credico, BSc, MD1, Ralph Hsiao, MSc2, Jaret Olson, MD, FRCSC3, Michael J. Morhart, MD4, Karyne N Rabey, PhD2, Christine A Webber, PhD2 and Matthew WT Curran, MD5, 1University of British Columbia, Vancouver, BC, Canada, 2University of Alberta, Edmonton, AB, Canada, 3Plastic and Reconstructive Surgery, University of Alberta, Edmonton, AB, Canada, 4Department of Plastic and Reconstructive Surgery, University of Alberta, Edmonton, AB, Canada, 5Plastic and Reconstructive Surgery, Princess Alexandra Hospital, Woolloongabba, QLD, Australia
Introduction
Spinal cord injuries (SCI) are devastating injuries that can significantly impair the function of patients. Nerve transfers are a technique of nerve reconstruction that has been described to attempt to improve their function. The axillary to radial nerve transfer is an uncommon transfer; however, it is becoming popularized in suitable SCI patients to assist with transfers. However, there are questions of how to optimize this transfer including the ideal branch for transfer. This study was conducted to better determine the anatomic variation of the axillary nerve and the suitability of its motor branches for transfer.
Materials and Methods
12 cadavers were used for the dissection of the axillary nerve branches after exiting the quadrangular space. An anterior and posterior approach was used to fully dissect the deltoid and count each branch. The length was measured from the quadrangular space to the muscular insertion and then determined if a nerve graft would be required to make the transfer feasible. Data was calculated as mean and standard deviation. Comparisons between branch groups were made with ANOVA and Bonferroni correction for post-hoc analysis. Significance was defined as (p <0.05).
Results
There was a total of 7 females and 5 males with an average age of 87.8 ± 7.4 years. The mean number of branches were 3.3 ± 1.9 to the posterior, 4.8 ± 2.3 to the middle and 2.6 ± 1.6 to the anterior head which were significantly different (p=0.01). Additionally, there was a significant difference in average length at 55.33 ± 13.36mm, 53.69 ± 11.42mm and 80.46 ± 15.11mm respectively (p<0.001). 78% of all branches had sufficient length to reach the radial nerve (89% posterior, 59% middle and 97% anterior) while the others would require a nerve graft.
Discussion
Spinal cord injuries most commonly occur at the level of C6 resulting in loss of elbow extension as well as extension/flexion of the digits. There was significant redundancy in all branches to the anterior, middle and posterior heads of the deltoid with the middle demonstrating the most branches. Multiple branches of the posterior and middle branches would not require an interpositional graft. The axillary to radial nerve transfer is a promising option in mid-cervical tetraplegic patients. This study represents an initial step in optimization of the transfer. In order to refine the surgical technique, further studies including axon counts to identify the best nerve match are currently underway.
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