Bone graft revascularization strategies

Reconstruction of avascular necrotic bone by pedicled bone grafting is a well-known treatment with little basic research supporting its application. A new canine model was used to simulate carpal bone avascular necrosis. Pedicled bone grafting proved to increase bone remodeling and bone blood flow, supporting its use in clinical practice.
The risk for complications, including infection, fracture and non-union, in conventional segmental bone allografts is high due to absent vascular ingrowth and limited bone formation. A new rat model with intramedullary implantation of an arteriovenous bundle, defined as surgical revascularizaton, is presented. This technique effectively revitalizes the necrotic state of conventional allografts, without disturbing biomechanical properties, which could offer a beneficial adjunct to clinical bone grafting.
In order to increase cryopreserved allograft angiogenesis and osteogenesis, FGF-2 and VEGF were delivered intramedullary in biodegradable microspheres to secure continuous release of growth factor. FGF-2 exerts minor angiogenic or osteogenic potential while VEGF increases bone blood flow and bone remodeling at both short and long term analyses. Applying a new orthotopic model, microsphere encapsulated VEGF proves to increase bone remodeling, which could potentially prevent long term complications associated with conventional bone allografting.
By combining a gender mismatch rat model, fluorescent labeling, laser capture microdissection and reverse transcriptase polymerase chain reaction, the presence of donor and acceptor derived cells (cell lineage) within vascularized autografts and vascularized allografts was determined. Furthermore, delivery of VEGF intramedullary was found to influence cell lineage in distinct bone remodeling areas within vascularized bone allografts. These findings offer new insights into the physiologic processes following vascularized bone autografting and allografting.