NEOVASCULARIZED BONE GRAFTS: EXPERIMENTAL INVESTIGATION RICCARDO BUSA, M.D., 1 * ROBERTO ADANI, M.D., 2 CLAUDIO CASTAGNETTI, M.D., 1 DAVIDE ZAFFE, M.D., 3 and ANTONIO MINGIONE, M.D. 2 Vascularized bone grafts are standardized procedures in re- constructive surgery but there are some disadvantages: do- nor site morbidity, limited number of “natural” donor sites, and complex technique. In this study, we test the possibility of creating a “neovascularized” bone graft utilizing a vascular implantation procedure in a rabbit model. Sixteen New Zeal- and adult white rabbits were used. In each animal, two iliac crest bone grafts (7 × 7 × 10 mm) were harvested. Vascular implantation of the right superficial femoral vessels was per- formed in one of the two grafts, which was wrapped in a silicone envelope to avoid neovascularization from the sur- rounding tissues and positioned in a subcutaneous pocket in the right medial thigh. On the left side, the bone block, wrapped in the silicone envelope, was buried subcutane- ously without vascular implantation. The operated animals were divided into two groups: Group I included eight rabbits explanted 4 weeks postoperatively and Group II included eight rabbits explanted 8 weeks postoperatively.Tetracycline injection was performed 72 hours preexplantation to evaluate new bone formation. Selective colloidal ink injection in the axial artery was performed to investigate the neovasculariza- tion before inclusion in poly-methyl-methacrylate (PMMA). Histological examination was performed in all explanted specimens comparatively. Histological examination 8 weeks after surgery showed a marked neovascularization, with nor- mal bone cells. Tetracycline labeling showed new bone for- mation with a normal pattern. In all nonvascularized speci- mens, no viable cells or neovascularization and no bone for- mation were found. The vascular implantation procedure can induce a good neovascularization with new bone formation in a small bone graft. The possibility of neovascularization in- duction by the simple vascular implantation procedure has several clinical implications in reconstructive surgery. © 1999 Wiley-Liss, Inc. MICROSURGERY 19:289–295 1999 Bone defects can be treated by various reconstructive pro- cedures including bone grafts.Vascularized bone grafts have the advantage of quicker consolidation and greater mechani- cal strength and resistance to infections. 1–4 Today, the vas- cularized bone graft procedure is a standard in reconstruc- tive surgery. 5,6 However, this procedure has limitations, such as the morbidity of the donor site, the shape, the struc- ture, and the mandatory site of the available bone. 2,7 Neovascularization is a neoangiogenetic phenomenon observed in many reparative and proliferative biological processes that is prompted by growth factors currently un- dergoing study. 8,9 Tissue neovascularization can be induced by vascular implanting procedures. 10 The first studies in vascular induction to the bone tissue were fundamentally aimed at overcoming the problems rep- resented by avascular necrosis. 1,10–12 This line of study has led to the development of several vascular implanting pro- cedures, especially for Kienbock’s disease. 13 On the basis of the results achieved in this field, some authors 14–16 have used vascular implanting procedures to obtain composite vascularized grafts for reconstruction of multiple tissue loss. The creation of a number of experimental models has made it possible to show that fragments of cancellous bone implanted in a capsule crossed by an arteriovenous vascular axis are not subject to necrosis. On the contrary, they show direct and indirect signs of neovascularization and neo- osteogenesis. 2–4 The biological bases of these data are un- known. Given the interest shown in these results, we at- tempted to evaluate an experimental model for the study of bone neovascularization inducible by means of a vascular implanting procedure that could prove interesting and useful both biologically and clinically. In our model, vascular implantation in a small bone graft is associated with silicone sheet wrapping in order to “iso- late” the graft from the surrounding tissue and prevent any neovascularization supply from surrounding tissues. MATERIALS AND METHODS The study was performed on 16 male New Zealand rab- bits, aged 12 months and weighing between 4.5 and 5.5 kg, in compliance with current regulations concerning experi- ments on animals. The surgical procedure was performed under general anesthesia and in sterile conditions at the local animal breeding department. The histological assess- 1 Unita ` Operativa di Chirurgia della Mano, University of Modena, Modena, Italy 2 Clinica Ortopedica e Traumatologica, University of Modena, Modena, Italy 3 Dipartimento di Scienze Morfologiche e Medico-Legali, Sezione di Anatomia Umana, University of Modena, Modena, Italy *Correspondence to: Dr. Riccardo Busa, M.D., Stradello Bernarda 89, 41010 San Damaso, Modena, Italy. E-mail: r.busa@mo.nettuno.it © 1999 Wiley-Liss, Inc.