Anatomical bases of the posterior approach to the brachial plexus for repairing avulsed spinal nerve roots

Abstract

Avulsion of nerve roots from the cervical spinal cord has always been considered as an untreatable injury, even by surgeons with expertise in this area. However, numerous experimental studies in animals, as well as a human case report, showed that if continuity is restored between the spinal cord and nerve roots, axons from spinal motor neurons can regrow into the peripheral nerve graft with a subsequent recovery of motor function. The posterior subscapular approach, based on the evolution of the posterolateral approach for removal of the first rib, is the only way to expose the entire brachial plexus from C5 to T1 from the ventral and dorsal roots to the distal nerve trunks. The purpose of this study is to investigate the topographic anatomy of the brachial plexus, with particular emphasis on the relationships important to the posterior approach and reimplantation of the ventral rootlets within the cord, either directly or using peripheral nerve grafts. The major advantage of the procedure is the proximal exposure of the plexus, with evaluation of the lesions being excellent (intradural, foraminal and proximal trunks). Reimplantation of ventral roots into the cord is relatively easy from C5 to C7, more difficult for C8 and problematic for T1, whereas reimplantation of dorsal roots into the cord is easy from C5 to T1. The disadvantages of this approach for exposure of the plexus and nerve root avulsion repair are significant: the surgical technical steps are difficult mainly because of the cervical paraspinal muscle mass, which cannot be easily "elevated and retracted" despite previous descriptions; bleeding from the venous plexus can be excessive as suggested by dissection and our own experience; the stability of the cervical spine may be compromised following extensive laminectomy with total unilateral facetectomy; exposure of the plexus distal to the division of the trunks is difficult; there may be injury to the long thoracic nerve and subsequent winging of the scapula; and pneumothorax. This approach is therefore only applicable in highly selected cases involving multiple avulsed roots with proximal lesions extending as far as the division of the trunks.