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Reconstruction Of Craniofacial Structural Defects Through Patient-specific 3d-printed Custom Beta Tricalcium Phosphate Scaffolds: Development Of A Translational Porcine Model
Richard Guidry, BS1, Silpa Sharma, MPH1,2, Daniel Yoo, MD1, Luis Marrero, PhD3, Catherine Takawira, MS4, Bruce Bunnell, PhD5, Mandi J. Lopez, DVM PhD4, Gerhard S. Mundinger, MD FAAP1,2.
1Division of Plastic Surgery, Louisiana State University Health Sciences Center, New Orleans, LA, USA, 2Children's Hospital of New Orleans, New Orleans, LA, USA, 3Department of Orthopedic Surgery, Louisiana State University Health Sciences Center, New Orleans, LA, USA, 4Laboratory for Equine and Comparative Orthopedic Research, Louisiana State University, Baton Rouge, LA, USA, 5Tulane Center for Stem Cell Research and Regenerative Medicine, Tulane University, New Orleans, LA, USA.

PURPOSE: 3D-printed bone scaffolds can be commercially printed within days using CT guidance to reconstruct complex craniofacial bony defects. Additional autologous stem cell seeding of scaffolds may enable improved regeneration of normal bony architecture. However, the ability of 3D-printed scaffolds to regenerate load-bearing bone is untested in large animal models.
METHODS: A craniofacial porcine model was developed testing the ability of custom 3D-printed bone scaffolds to heal non-critical (<6 cm) and critical (>6 cm) bony defects in Yucatan pigs. Simultaneous full-thickness defects were made in the body of the right zygoma (2 cm) and the angle of the left mandible (6 cm) using custom cutting guides. In the negative control (n=4), no construct was placed (Fig. 1). In the experimental arm (n=8), beta-tricalcium phosphate (β-TCP) defect-specific bone scaffolds were 3D-printed from preoperative CT scans and placed into bony defects based on promising in vitro cell adhesion and viability assays (Fig. 2). Animals were followed until a six-month study endpoint obtaining CT imaging at three and six months. After surgical site explanation, bony regeneration was evaluated histologically and via μCT scanning. Additional bone strength testing was performed on implant cores.
RESULTS: All animals reached the 6-month study endpoint. In the negative control group, CT and gross evaluation of zygomatic and mandibular defects was consistent with incomplete heterotopic ossification. Massonís trichrome staining, picrosirius staining, and μCT confirmed the presence of dystrophic bone formation at the ostomy sites with disruption of normal bone architecture compared to control sites. Biomechanical testing was not performed due to inadequate regeneration. In the experimental arm, scaffolds maintained high fidelity to preoperative surgical plan with CT evidence of bone regeneration at three months. Evaluation at study endpoint demonstrated bone regeneration throughout the implants with bony integration at the implant/native bone interfaces. Histologic, μCT and biomechanical testing is ongoing.
CONCLUSION: Our model has broad applicability in preclinical evaluation of bone regeneration scaffolds. 3D-printed, defect-specific β-TCP scaffolds demonstrated biocompatibility with bone regeneration and osseointegration. Insights from this model may realize the possibility of reconstructing bony defects of any size, shape, and thickness by harnessing the power of 3D-printing and autologous stem cell seeding for congenital, post-traumatic, and oncologic reconstruction.


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