Surgical revascularization induces angiogenesis in orthotopic bone allograft basic research

Background: Remodeling of structural bone allografts relies on adequate revascularization, which can theoretically be induced by surgical revascularization. We developed a new orthotopic animal model to determine the technical feasibility of axial arteriovenous bundle implantation and resultant angiogenesis. Questions/purposes: We asked whether arteriovenous bundles implanted in segmental allografts would increase cortical blood flow and angiogenesis compared to nonrevascularized frozen bone allografts and contralateral femoral controls. Methods: We performed segmental femoral allotransplantation orthotopically from 10 Brown Norway rats to 20 Lewis rats. Ten rats each received either bone allograft reconstruction alone (Group I) or allograft combined with an intramedullary saphenous arteriovenous flap (Group II). At 16 weeks, we measured cortical blood flow with the hydrogen washout method. We then quantified angiogenesis using capillary density and micro-CT vessel volume measurements. Results: All arteriovenous bundles were patent. Group II had higher mean blood flow (0.12 mL/minute/100 g versus 0.05 mL/minute/100 g), mean capillary density (23.6% versus 2.8%), and micro-CT vessel volume (0.37 mm ³ versus 0.07 mm ³ ) than Group I. Revascularized allografts had higher capillary density than untreated contralateral femora, while vessel volume did not differ and blood flow was lower. Conclusions: Axial surgical revascularization in orthotopic allotransplants can achieve strong angiogenesis and increases cortical bone blood flow. Clinical Relevance: Poor allograft revascularization results in frequent complications of nonunion, infection, and late stress fracture. The presented technique of surgical revascularization could therefore offer a beneficial adjunct to clinical segmental bone allografting.