Comparative study of autologous bone graft and bone morphogenetic protein-2 for bone regeneration using a novel rabbit Masquelet technique model.

The Masquelet technique is widely used for reconstructing critical-sized bone defects; however, autologous bone grafting (ABG) is associated with donor-site morbidity such as pain and bleeding. Bone morphogenetic protein-2 (BMP-2) has attracted attention as a potential alternative strategy for promoting bone regeneration. Studies on direct comparisons between BMP-2 and autologous bone grafting within the context of the Masquelet technique are limited. The purpose of this study was to establish a novel rabbit femoral Masquelet model and compare the bone regenerative capacity of ABG with β-tricalcium phosphate (β-TCP) loaded with BMP-2. A 20-mm segmental defect was created in the femur of 24-week-old New Zealand White rabbits and stabilized with a locking plate. The defect was filled with polymethyl methacrylate cement, which was removed four weeks later to induce membrane formation. The defect was subsequently filled with autologous iliac bone (ABG group) or β-TCP granules containing BMP-2 (BMP-2 group). Bone regeneration was evaluated 12 weeks after the second surgery using radiographic, histological, micro-computed tomography (μCT), and biomechanical analyses. Radiographic evaluation demonstrated satisfactory bone union in both groups, without substantial difference in union rate. Histological analysis showed cortical continuity and new bone formation in both groups. μ-CT revealed that the bone volume/tissue volume ratio of total calcified callus was significantly higher in the ABG group, whereas the tissue mineral density was significantly higher in the BMP-2 group. Biomechanical testing showed no significant differences in ultimate stress, extrinsic stiffness, or failure energy between the two groups. In this rabbit femoral Masquelet model, BMP-2 delivered with β-TCP achieved bone regeneration comparable to that of autologous bone grafting. These findings suggest that BMP-2 may represent a promising option for bone reconstruction using the Masquelet technique.