Invaginated vein graft as nerve conduit: an experimental study

Vein grafts have been used for nerve repair in experimental and clinical studies. However, some concerns about their collapsability and the presence of valves which could block axonal growth have been put forth. We propose a modification to eliminate these potential problems by turning the vein inside out, obtaining an "invaginated" vein graft. We performed an experimental study on 61 adult Wistar rats, divided into 3 groups: control (non-operated) (n = 11); immediate repair, with 3 subgroups: invaginated vein graft (n = 10), vein graft (n = 10), and nerve graft (n = 10); and delayed repair, with 2 subgroups: invaginated vein graft (n = 10) and nerve graft (n = 10). Delayed repair was performed 3 to 4 weeks following division of the nerve. Electromyographical (EMG) assessment was performed in all operated animals at 2, 4, and 6 months after immediate reconstruction, and at 1 and 4 months after delayed repair. At the end of the study, all nerves were excised and a morphometric analysis was performed. We conclude that vein grafts are as useful as nerve grafts in immediate and delayed nerve repair, as there were no significant functional or histologic differences. We found no significant differences between invaginated vein grafts and non-invaginated vein grafts. However, electrophysiological results were slightly superior in the former. Regenerated axons were small, grouped in minifascicles with thin myelin sheaths. The venous adventitia did not interfere with axonal growth.