In Vivo Comparison of Two Bone Substitutes in the Distal Femur of the Rabbit

Purpose: This study aimed to microradiographically evaluate the healing of grafted defects using a surgically standardized model that was suitable for comparing the regenerative potential of different grafts. Materials and Methods: Two different biomaterials, bovine porous bone mineral (BPBM) and nanohydroxyapatite (NHA), were used to fill defects produced in the distal epiphyses of 10 adult male rabbits for 2 and 4 months. Three rabbits were left untreated, without defects, as controls. Evaluations were performed on microradiographs of sections of polymethyl methacrylate-embedded rabbit epiphyses. The amounts of graft material and bone were evaluated by splitting the filled hole into three portions. Results: A greater amount of BPBM granules were in contact with bone at both 2 and 4 months versus the NHA (statistically significant difference in the central portion of the defect), and a persistence of the BPBM over time was apparent. The amount of NHA decreased from the inner to the outer portion of the defect, particularly after 4 months. The bone amount increased from the inner to the outer portion, particularly for the NHA graft, which produced an early cortex. The amount of mineralized material reached about 80% in the BPBM and 40% to 60% in the NHA after 4 months. Conclusion: Both the analyzed biomaterials performed adequately for bone regeneration. The two biomaterials are probably suitable for grafting defects related to early cortical formation or spacemaintaining clinical requirements. Keywords: bone regeneration, bovine porous bone mineral, microradiography, nanohydroxyapatite, rabbit femur