Long-Term Evaluation of Rat Peripheral Nerve Repair With End-to-Side Neurorrhaphy

Abstract

This study was designed to assess long-term reinnervation of end-to-side neurorrhaphy in the rat. The cut right peroneal nerve was repaired and sutured to the side of the intact tibial nerve. Both the extent of reinnervation and the integrity of the intact donor nerve were evaluated in 48 Sprague-Dawley rats randomly treated with fresh or delayed nerve repair with or without perineurotomy. Evaluations included nerve conduction velocity (NCV) of both the peroneal and tibial nerves, dry muscle weight, and histologic examination (neurofilament stain and morphometric assessment) at 8 and 12 months postoperatively. Although animals treated with perineurotomy tended to have better NCV and dry muscle weight recovery than those without, the difference was not statistically significant. No difference was observed between fresh and predegenerated nerve repair. The mean total (all four subgroups) NCV recovery rates were 87 percent and 94 percent for the peroneal nerve, and 93 percent and 95 percent for the tibial nerve, compared to the contralateral intact nerves, at 8 and 12 months, respectively. Tibialis anterior muscle mass measurements revealed a recovery in dry muscle weight of about 85 percent and 89 percent at 8 and 12 months, respectively, compared to the intact contralateral tibialis anterior muscles. Histologic studies with neurofilament staining revealed numerous axons at the distal end of the peroneal nerve in all groups, indicative of myelinated axonal regeneration. Morphometric analysis demonstrated that the presence of a window in the perioneurium improved the histologic picture. The mean number of myelinated fibers at 12 months postoperatively was significantly higher in animals with a perineurotomy window (compared to without) in both fresh and predegenerated nerve repair subgroups, respectively (p <0.05). These results indicated that end-to-side neurorrhaphy permits axonal regeneration from the intact donor nerve and is associated with satisfactory recovery. The effect of the procedure on the donor nerve was negligible.

Influence of Breaching the Connective Sheaths of the Donor Nerve on Its Myelinated Sensory Axons and on Their Sprouting into the End-to-Side Coapted Nerve in the Rat

“…71 Accordingly, the structure and function of muscles innervated by the donor nerve and the donor nerve itself completely recovered at 6-12 months after surgery. 53,66,69,72,73 Together, these observations support the view that end-to-side nerve coaptation has no major detrimental long-term effect on the donor nerve. This is in accordance with two recent reports of clinical case series, 18,22 in which none of patients had any sensory or motor loss in the innervation zone of the donor nerve, even though perineurial sutures were made after the creation of a perineurial window in the donor nerve.…”

“…12,13,29,[48][49][50]54 but not later from 4 up to 8 months after surgery. 16,51,53,64 Interestingly, if epineurial or perineurial windows were enlarged from 1 to 4 or 5 mm, respectively, then, also, the magnitude of axonal ingrowth into the recipient nerve was increased. 65,66 Subepineurial focal degeneration and demyelination of the donor nerve distal to the site of coaptation in experimental groups Notably, bimodality coefficient > 0.555 indicates that a distribution is bimodal 56 (but see Jackson, P.R., Tucker, G.T., and Woods, H.F. (1989).…”

“…46,47 Creating an epineurial or perineurial window in the donor nerve at the site of end-to-side nerve coaptation with sutures enhanced the sprouting of motor and sensory axons into the recipient nerve in some studies, 12,13,16,29,[48][49][50] but not in others. 35,[51][52][53][54] The effects of either epineurial or perineurial window on the axonal sprouting into the recipient nerve were directly compared in only two studies. In one, the number of axons in the recipient nerve was higher in the group with a perineurial window, 48 whereas in the other there was no significant difference regarding the number of sensory and motor neurons retrogradely labeled through the recipient nerve.…”

A histomorphometric study of unmyelinated fibers of the fibular nerve in Wistar rats

“…The use of the fibular nerve in studies of nerve regeneration was boosted after the reintroduction of the end-to-side neurorrhaphy 1,2,3,4,5,6,7,8,9,10,11,23,13 . We were not able to find many references to the unmyelinated axons of the fibular nerve in these and other recent studies.…”

Terminolateral Neurorrhaphy between Somatic Nerve and Autonomic Nerve

“…In fact, when there is no injury to the donor nerve, nerve regeneration can occur following endto-side anastomosis, but several experimental studies have shown that when the donor nerve had a fenestration, the effect of nerve regeneration was better [71][72][73][74]. Although there are still controversies over whether fenestration can damage the donor nerve, many studies have confirmed that the fenestration of the epineurium can cause a slight damage to the donor nerve, but does not affect the donor nerve function [75][76][77]. this approach does not cost the donor function when nerve grafting.…”