Peripheral Nerve Revascularization: Histomorphometric Study of Small‐and Large‐Caliber Grafts

Abstract

The revascularization of nerve grafts was investigated using histologic and morphometric techniques. Small-diameter nerve grafts (sciatic in the rat and sural in adult ewes) were studied, as was a large-diameter peroneal nerve 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 their control nerves, suggesting that spontaneous revascularization had occurred 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 days 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 neural regeneration at 40 days. The finding suggests that small-diameter nerve grafts spontaneously revascularize, and revascularization using microvascular techniques is not necessary. In contrast, the larger-diameter nerve graft did not revascularize well. Such a large-diameter nerve graft would provide a suitable model to investigate the potential merits of a vascularized nerve graft.

Comparison of Acellular Nerve Allograft Modification with Schwann Cells or VEGF

“…The ANA-SC and ANA-VEGF were higher compared to the ANA, but not significantly different (25.9±6.4 and 28.5± 5.6 %, respectively). Density was similar across all groups at the midgraft, ranging 27,698-34,478 fibers/mm 3 . Fiber width ranged 2.8-2.9 μm and was not significantly different across the groups.…”

“…All of the groups showed similar widths in the range of 2.3-3.2 μm. Normal rat sciatic nerve has a nerve fiber density of 11,882 fibers/mm 3 and an average fiber width of 6.5 μm [29].…”

Challenges in sciatic nerve repair: anatomical considerations

“…13 Doubt about peroneal branch sacrifice arises from concerns of vascularization of this relatively large-bore nerve. 6 Furthermore, as improvements in peroneal branch restoration are made, this method will become less favorable. Heading in a different direction, an option would be to look for alternative autologous nerves.…”

Surgical Treatment of Peripheral Nerve Injury

“…Small-diameter grafts spontaneously revascularize, but large-diameter grafts do so incompletely (45) . Thick grafts undergo central necrosis with subsequent endoneurial fibrosis.…”