Nerve grafting and end-to-side neurorrhaphies connecting phrenic nerve to the brachial plexus

End-to-side coaptation--controversial research issue or important tool in human patients

End-to-side coaptation is still a controversial procedure. Many authors reported surprisingly good results; others showed mediocre results only. There are also reports of complete failures. Apparently all authors are right. According to our experience the results depend on the level of end-to-side coaptation and on the nerve fiber composition. End-to-side coaptation between mixed nerves do have very poor expectations. The chances are much better if e.g. a small denervated pure motor nerve is coapted to a functioning small pure motor nerve. The same procedure may produce opposite results according to the circumstances. In our experience end-to-side coaptation is a reliable procedure of great use in selected cases. Main field of application are thin nerves with a well defined function and synergistic terminal motor branches.

Nerve fiber transfer by end-to-side coaptation

To bring some light into the ongoing controversy concerning end-to-side coaptation in brachial plexus surgery, the authors organized a symposium in 2006 titled How To Improve Peripheral Nerve Surgery. The authors sought the participation of experienced surgeons and researchers who had made personal contributions to the field. This article contains information collected at this symposium and presents the authors' clinical results and ideas illustrating the potential of nerve fiber transfer by end-to-side coaptation.

The use of end-to-side nerve grafts to reinnervate the paralyzed orbicularis oculi muscle

Facial paralysis is a serious neurologic disorder, particularly when it affects the eye. Loss of the protective blink reflex may lead to corneal ulceration and, possibly, visual loss. The purpose of this study was to compare different nerve-grafting techniques to reanimate the paralyzed eyelid. Sixteen adult dogs (25 kg each) were allocated into four groups. Denervation of the left hemi-face was performed in all cases. One dog served as a control animal (group I). Group II dogs (n = 5) underwent end-to-side coaptation of the nerve graft to the intact palpebral branch and end-to-end coaptation to the denervated palpebral branch. Group III dogs (n = 5) underwent end-to-end coaptation of the nerve graft to the intact palpebral branch and end-to-end coaptation to the denervated palpebral branch. Group IV dogs (n = 5) underwent end-to-side coaptation of the nerve graft to the intact and denervated palpebral branches. The animals were monitored for 9 months after the surgical procedures, to allow adequate time for reinnervation. The dogs were postoperatively monitored with clinical observation, electrophysiologic testing, video motion analysis, and histologic assessments. Clinical observation and electrophysiologic testing demonstrated the production of an eye blink in the denervated hemi-face in all experimental groups. There was a trend toward increased speed of reinnervation for group III animals (end-to-end coaptations). It was concluded that end-to-side coaptation can produce a contralateral synchronous eye blink in a clinically relevant, large-animal model.

Recovery of cutaneous pain sensitivity after end-to-side nerve repair in the rat

OBJECT

The hypothesis that collaterally sprouting axons from an uninjured donor nerve may provide recovery of pain sensitivity in the skin after end-to-side nerve repair was investigated in rats. In addition, the effect of this technique on the donor nerve was examined.

METHODS

The distal stump of the transected peroneal nerve was sutured end to side to the intact sural nerve. No epineurial window or perineurial slit was made in the sural nerve at the site of coaptation. Other nerves in the leg were transected and ligated. Eighteen weeks later, the sural nerve was transected at a site distal from the coaptation site. The residual pain sensitivity in the peroneal innervation field in the instep was documented using the skin pinch test in three of 11 animals. The area of sensitivity encompassed 19 to 40% of the maximum nociceptive innervation area of the normal peroneal nerve. The nerve pinch test revealed functional sensory axons in all communicating peroneal nerves, in which 277+/-119 myelinated axons (mean +/- standard deviation) were found by histological investigation.

CONCLUSIONS

The authors conclude that at least partial recovery of sensory function due to collateral sprouting of axons after end-to-side nerve repair is possible in principle. However, the presence of functional sensory axons in the peroneal nerve stumps did not guarantee the recovery of skin sensitivity to pain in all animals. No functional or morphological evidence of an untoward effect of collateral sprouting into the end-to-side communicating nerve was detected in the axons of the donor nerve itself.

Variables affecting axonal regeneration following end-to-side neurorrhaphy

The concept that end-to-side nerve coaptation can induce collateral sprouting was recently reintroduced by Viterbo. However, other authors have reported conflicting results with this technique of nerve repair. The current paper studies some of the variables affecting axonal regeneration following end-to-side repair. The first part of the study compares the rate of axonal regeneration following end-to-side neurorrhaphy with nerve grafts using epineurial versus perineurial sutures. The rat sciatic nerve model was used and fresh autogenous nerve grafts were sutured to the side of intact sciatic nerves. A total of 20 rats were divided into 2 groups. In group A (n = 10), suturing of the nerve graft was done to the epineurium. In group B (n = 10), suturing was done to the perineurium. Histological and electron microscopic evaluation of the nerve grafts was done 50 days following the repair. In group A, none of the nerve grafts showed regenerating axons. In group B, 50% of grafts showed evidence of axonal regeneration. The difference between the two groups was statistically significant. Electron microscopy showed that the repair process following end-to-side neurorrhaphy was structurally similar to axonal regeneration following end-to-side neurorrhaphy. It was concluded that axonal regeneration following end-to-side nerve coaptation is more likely to occur when the nerve graft is sutured to the parent nerve using perineurial rather than epineurial sutures. The second part of the study focused on investigating the feasibility of inducing collateral sprouting by silicone tubes sutured in an end-to-side fashion to the epineurium or perineurium of intact sciatic nerves. Following a 50-day recovery period, the site of silicone tube attachment was exposed and the tube carefully removed. The silicone tube contained soft tissue which was firmly attached to the side of the nerve and this was called the Attached Soft Tissue Segment (ASTS). Histological and electron microscopic examination showed no evidence of any nerve regeneration within the ASTS. The failure to demonstrate collateral sprouting within the ASTS may be explained by the absence of Schwann cells in the transplanted silicone tubes.