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3D-printed bioactive ceramic scaffolds for the repair of critical-sized long bone defects: A large translational pre-clinical model
Vasudev Vivekanand Nayak, MSci, PhD
1,2, Jacques H. Hacquebord, MD
3,4, Lukasz Witek, MSci, PhD
5,6,7, Vishal D. Thanik, MD
3, Nicholas J Iglesias, MD
2, Hana Shah, BS
2, Sara Munkwitz, B.S.
1; Paulo G. Coelho, MD, DDS, PhD, MBA
1,2(1)University of Miami, Miami, FL, (2)University of Miami Miller School of Medicine, Miami, FL, (3)New York University Langone Health, New York, NY, (4)NYU Langone Health Department of Orthopedic Surgery, New York, NY, (5)New York University College of Dentistry, New York, NY, (6)New York University Tandon School of Engineering, Brooklyn, NY, (7)New York University Grossman School of Medicine, New York, NY
Background: Extensive extremity defects often exceeding 5 cm are typically reconstructed using autologous vascularized bone transfer. However, this technique presents challenges such as donor site morbidity, infection, and delayed healing. These limitations have spurred interest in alternative biomaterial applications. This study aimed to evaluate the efficacy of 3D-printed bioactive ceramic [?-tricalcium phosphate (?-TCP)] scaffolds augmented with dipyridamole (3DPBC-DIPY), an indirect A
2AR agonist known to promote bone formation, in stimulating bone regeneration in a critical-sized radius defect using an in vivo translational model.
Methods: 3DPBC-DIPY scaffolds were used to repair critical-sized defects in the tibial diaphysis of sheep (Ovis aries, N=8). Defects measuring ~7 cm in length and full thickness were created. The scaffolds, in a two-piece configuration, were implanted into the defect sites, along with an intramedullary rod. The animals were euthanized 24 weeks post-surgery, and tibiae were harvested en bloc. Bone regeneration within the scaffold pores was evaluated through histological analysis and micro-computed tomography (microCT) imaging/virtual reconstruction, while biomechanical properties were assessed through nanoindentation to measure elastic modulus (E) and hardness (H).
Results: MicroCT analysis demonstrated substantial osseous tissue in-growth throughout the porous architecture of the scaffolds following a 24-week implantation period, indicating robust bone regeneration and scaffold integration within the host tissue. Histological analysis revealed oriented bone in-growth directed toward the native bone interface, accompanied by extensive new bone formation and marked scaffold resorption with evidence of scaffold degradation. The regenerated bone tissue was localized within the confines of the defect site and scaffold regions, with no evidence of ectopic bone formation beyond these boundaries, yielding biomechanical properties (i.e., E and H) statistically homogenous to that of native bone (
p>0.05).
Conclusion: 3DPBC-DIPY scaffolds demonstrated biocompatibility, resorbability, and the capacity to support directional bone regeneration and remodeling within a segmental long-bone defect in a highly translational, large pre-clinical model.
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