Induction of Osteogenesis After BMP-2 Injection in Rabbit Shoulders: A Novel Strategy for Managing Glenoid Bone Defect Associated with Anterior Shoulder Instability

Abstract

Background: Bone morphogenic protein-2 (BMP-2) has been shown to promote bone formation. The purpose of this research was to determine if an injectable form of BMP-2 could induce bone formation in anteroinferior glenoid bone defects, which is a critical factor of anterior shoulder instability. The purpose of this study was to investigate bone formation in rabbit shoulders following BMP-2 injection into the anterior capsulolabral complex. We hypothesized that the amount of new bone would be greater in rabbit shoulders injected with BMP-2 than in those injected with normal saline. Methods: An experimental study was conducted on 40 shoulders of 20 mature rabbits. Twenty right shoulders were allocated to four groups according to injection dose (5 µg or 10 µg) and follow-up period after injection (4 or 8 weeks). Twenty left shoulders were injected with normal saline as controls. At 4 or 8 weeks after injection, all rabbits were sacrificed, and bone volumes, densities, and locations of bone formation were evaluated using micro-computed tomography (micro-CT). Histologic analysis was performed on all 40 shoulders. Results: Shoulders injected with BMP-2 showed significantly more bone formation than control shoulders in all treated groups (58.6 ± 60.5 mm3 vs. 25.6 ± 32.6 mm3, p = 0.001). Moreover, bone formation increased with dose and follow-up. Locations of bone formation were the lesser tuberosity, greater tuberosity, and anterior capsulolabral complex. Histologic analysis confirmed the micro-CT-detected bone formation by revealing the presence of activated osteocytes, abundant osteoblastic rimming, and woven bone matrix. Conclusion: The study confirms that BMP-2 injection into the anterior capsulolabral complex of rabbit shoulders promotes new bone formation in adjacent soft tissue areas. Study Design: Controlled laboratory study.