Intramarrow Bone Morphogenetic Protein 4 Gene Delivery Enhances Early Implant Stability in Femurs of Ovariectomized Rabbits

Background: Sufficient early implant stability is critical to prevent excessive micromovement of the implant during peri‐implant healing and to ensure the success of osseointegration. Implants placed in osteoporotic bones are often associated with low early implant stability. The purpose of this study is to determine the effects of intramarrow bone morphogenetic protein 4 (BMP4) gene delivery on early implant stability and peri‐implant healing. Methods: Adenoviruses encoding human BMP4 or LacZ were introduced into the femoral osteotomy sites immediately before implant placement in ovariectomized rabbits. The implant stability was determined by resonance frequency analysis at weeks 0, 4, and 8. Changes in cortical bone thickness and intrascrew bone formation at weeks 4 and 8 were evaluated by microcomputed tomography analysis and undecalcified histologic examination, respectively. Results: Intramarrow BMP4 gene delivery resulted in more improvement in implant stability at both weeks 4 and 8. Increased increment in peri‐implant cortical bone thickness and better intrascrew bone formation were found in the BMP4 group compared to the LacZ group. Conclusion: The results of this study suggest that intramarrow adenoviral gene delivery of BMP4 enhances peri‐implant bone healing and improves early implant stability in osteoporotic rabbit femurs.