Peripheral nerve revascularization: Histomorphometric study of small- and large-caliber grafts

The revascularization of nerve grafts was investigated using histologic and morphometric techniques. small-diameter nerve grafts (sciatic in the rat a nd sural in adult ewes) were studied, as was a large-diameter peroneal nerv e graft in the ewe. Ninety-six hours after sciatic nerve engraftment, rats were injected with an intravascular fluorescent tracer, Evans blue albumin (EBA). Specimens were observed for the number of Vessels perfused. Analysis showed no difference in vascular pattern between the grafted nerves and th eir control nerves, suggesting that spontaneous revascularization had occur red to establish a Vascular tree essentially identical to the native nerve. Sural and peroneal nerve grafts were evaluated in adult ewes at 7 or 40 day s post-nerve grafting. similar to the rat sciatic nerve, the small-diameter sural nerve grafts were completely revascularized, with an equal number of perfused vessels at both time periods, with respect to control specimens. In contrast, the larger-caliber peroneal nerve grafts were not perfused at 7 days, and very poorly perfused at 40 days. This correlated with scant neu ral regeneration at 40 days. The finding suggests that small-diameter nerve grafts spontaneously revascu larize, and revascularization using microvascular techniques is not necessa ry. In contrast, the larger-diameter nerve graft did not revascularize well . Such a large-diameter nerve graft would provide a suitable model to inves tigate the potential merits of a vascularized nerve graft.