Advanced neurorraphy techniques (from research to new therapies)

Nerve injuries were classified into three types by Seddon (neurapraxia, axonotmesis and neurotmesis) then classified by Sunderland into five degrees which overlap and provide more details to Seddon's classification. A sixth degree of injury has been described by MacKinnon , corresponding to a mixed pattern of injury (varying degrees of injury in different sections of the nerve). The present topic deals with advanced treatment methods of neurotmesis (fifth degree injury) which is a complete section of the nerve. Direct nerve repair with epi-perineural microsutures is still the gold standard surgical treatment for such lesion ; it is developed in a previous topic of this session. Surgical alternatives exist as well as ways to promote nerve repair. Neurotization by nerve transfers are also developed in a previous topic.

Autologous nerve grafting

Nerve grafting is indicated if primary end-to-end closure of the two transected nerve stumps is not possible without excessive tension. A section of nerve can be harvested and placed between the two stumps. In patients with large nerve gaps where injury must be bridged, use of an autograft remains the mainstay in spite of the lesion induced by the harvest of the transplant. In dogs, suitable donor site for autologous nerve grafts is often the cutaneous saphenous nerve.

End-to-side nerve repair

End-to-side nerve suture is an approach which could be used in cases where the proximal or the distal stumps are not available (for example in cases where it is very distant from the distal stump). For example, when the proximal nerve stump cannot be used, the distal stump is coapted to the side of an intact donor nerve. The donor nerve does not lose any function as axonal ingrowth proceed by collateral sprouting from the healthy nerve. The potential advantage of this technique is that donor site morbidity associated with nerve graft harvest is avoided and the distance travelled by regenerating axons is reduced. In the opposite, if the distal nerve stump cannot be reconnected, the proximal stump could be coapted to the side of an injured nerve to reinforce recovery of one function. [...]