Transfer of axillary nerve branches to reconstruct elbow extension in tetraplegics: A laboratory investigation of surgical feasibility

Abstract

In spinal cord injuries at the C6 level, elbow extension is lost and needs reconstruction. Traditionally, elbow extension has been reconstructed by muscle transfers, which improve function only moderately. We have hypothesized that outcomes could be ameliorated by nerve transfers rather than muscle transfers. We anatomically investigated nerve branches to the teres minor and posterior deltoid as donors for transfer to triceps motor branches. In eight formalin-fixed cadavers, the axillary nerve, the teres minor branch, the posterior deltoid branch, the triceps long and upper medial head motor branches, and the thoracodorsal nerve were dissected bilaterally, their diameters measured and their myelinated fibers counted. To simulate surgery, using an axillary approach in two fresh cadavers, we transferred the teres minor or the posterior deltoid branch to the triceps long head and to the thoracodorsal nerve. The posterior division of the axillary nerve gave off the teres minor motor branch and then the branch to the posterior deltoid, terminating as the superior lateral brachial cutaneous nerve. The diameters of the teres minor motor branch, posterior deltoid, triceps long and upper medial head branches, and the thoracodorsal nerve all were ∼2 mm, with minimal variation. The nerves varied little in their numbers of myelinated fibers, being consistently about 1,000. Via an axillary approach, either the teres minor or the posterior deltoid branch could be transferred directly to the thoracodorsal nerve or to triceps branches without any tension.

Nerve transfers for elbow and finger extension reconstruction in midcervical spinal cord injuries

“…18 The high number of peripheral-type injuries we observed reinforces our initial belief that patients with tetraplegia should undergo operations within 1 year of their trauma. [3][4][5][6] Of interest was the potential for improvement, even after 18 months of peripheral palsy, following a distal nerve transfer. We have deemed palsy to be of peripheral origin when intraoperative electrical stimulation of a given motor branch produced no muscle contraction.…”

“…This was corrected postoperatively, allowing patients to use their upper limb above horizontal. An interesting observation was that the anterior division of the axillary nerve, which innervates the anterior and middle deltoid muscles, 6 was preserved in all patients, whereas posterior deltoid muscle innervation was impaired in 4 upper limbs. This suggests that the anterior deltoid muscle receives substantial innervation from the C-5 spinal cord level, which was not damaged in our patients.…”

“…[3][4][5][6] In spinal cord injuries, the use of nerve transfers is very new, and no clinical series have yet been published. In this paper we report our results on nerve transfers to reconstruct elbow, thumb, and finger extension in 13 upper limbs from 7 patients with tetraplegia.…”

“…4 In the present series, in no instance did we identify strong contractions of the teres minor nerve upon nerve stimulation, so we proceeded to harvest the entire posterior division of the axillary nerve, which also innervates the posterior deltoid muscle. 6 We had not attempted this before, because we were afraid of losing the posterior deltoid muscle as an option for transfer in case of failure. This is no longer of major concern because of the predictability of triceps muscle reinnervation by nerve transfer.…”

“…The supinator nerve shares its level of innervation with wrist extensors. 6 Hence, the stronger wrist extension is, the better supinator nerve quality is. However, we observed that even patients with weak wrist extension (i.e., Grade M3) can benefit from supinator nerve transfer.…”