Revascularization of peripheral nerve autografts and allografts

The timing and mechanisms of peripheral nerve revascularization were invest igated using a 2-cm sciatic nerve graft model in 55 rats. Epineurial perfus ion was consistently established by 48 hours and endoneurial perfusion by ' 72 hours. The pattern of endoneurial perfusion was "all-or-none"- either al l or none of the vessels in a fascicle exhibited blood flow. Conventional a llografts exhibited similar revascularization dynamics and patterns. Cappin g the ends of the autograft with Silastic significantly delayed revasculari zation; no now was observed at 4 days, and only a peripheral rim of perfuse d fascicular vessels was observed at 7 days. These patterns suggested that the primary method of revascularization in the conventional graft was longi tudinal inosculation; no evidence of peripheral neovascularization or depen dence on the graft bed as a source of revascularization was observed. The i ntroduction of a major histocompatibility complex barrier between the graft ed tissue and the recipient animal did not alter the timing or the mechanic s of blood flow reestablishment.