How do the principles of primary nerve anastomosis apply to nerve grafting for the treatment of spinal accessory nerve (SAN) injury, and is the use of nerve fascicles from the upper trunk a viable technique?

Updated: Mar 04, 2020
  • Author: Rohan R Walvekar, MD; Chief Editor: Arlen D Meyers, MD, MBA  more...
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Answer

The principles of primary nerve anastomosis also apply to graft interpositioning. Both proximal and distal nerve ends must be cleanly cut so that the fascicles are visible. The nerve graft is interpositioned in the reverse direction (ie, the proximal graft end attached to the distal free end of the nerve and vice versa). Nerve fascicles progressively branch and diverge distally, so reverse interpositioning promotes "funneling" of the regenerating axons from proximal to distal through the graft. [50]

Mayer et al described an SAN repair procedure using nerve fascicles from the upper trunk that are associated with axillary nerve function. In the study’s five patients, the investigators found improvement in the active ROM in shoulder abduction from a mean 55° preoperatively to 151° postoperatively. Moreover, the average pain level, reported as 6.8 preoperatively on the visual analogue scale, fell to 0.8 following surgery. [57]

Because grafting requires nerve axons to regenerate across 2 sites (proximal and distal), outcomes were previously believed to be inferior to those with primary anastomosis (ie, with only one site of end approximation). However, this hypothesis has been disproved; a tension free graft inter-positioning will lead to superior outcomes when compared with a tension-laden primary anastomosis. In addition, thinner nerve grafts such as cutaneous nerve grafts are more easily revascularized than thicker grafts, thus leading to better outcomes. [50]


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