LAUSR

Inside out vein graft is a well described method to create, in experimental setting, a biologic conduit for nerve regeneration studies. It consists in pulling the vein through itself to invert the normal orientation and place the intima outside and the adventitial layer within the lumen of the conduit. The reason for employing this technique is a presumed role of adventitial layer in helping nerve regeneration by providing an environment rich in collagen, laminin, and Schwann cells and promoting vascularization and a lower risk of conduit collapse during nerve regeneration. Other studies support the idea that there is no difference between standard vein graft or inside-out vein graft in terms of nerve regeneration, but anyway, in case of studies with cells addition in the conduit, there is less risk of leakage through side branches of the vein, that collapses in case of inside out. Even the risk of axonal sprouting in side branches of the vein, during nerve regeneration, is reduced. Pulling the vein through itself is not always easy, particularly when dealing with small veins such as external jugular vein of the rat. We have contrived a little trick to make this procedure very fast and easy. We put the vein on a 24G Abbocath, in which we have realized a little beveled incision on the proximal side (Fig. 1A). Then we move the vein on the proximal side of the incision (Fig. 1B). At this point we make the distal end of the vein lean on the abbocath incision. With a single movement we pull away the proximal end of the vein which goes over the distal end, that is kept fixed by the incision, inverting the conduit surfaces (Fig. 1C). Then, it is possible to unthread the vein from the abbocath and use it as a conduit for nerve bridging. With this little trick pulling the vein inside out takes about 30 seconds and doesn’t create any damage on the vessel.