Plastic Surgery Research Council

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3D-Printed Hyperelastic Bone in a Rat Critical Sized Calvarial Defect
Sumanas W. Jordan, MD, PhD1, Yu-hui Huang, MS2, Adam E. Jakus, PhD3, Linping Zhao, PhD2, Ramille N. Shah, PhD3, Pravin K. Patel, MD2.
1The Ohio State University, Columbus, OH, USA, 2University of Illinois at Chicago, Chicago, IL, USA, 3Northwestern University, Chicago, IL, USA.

PURPOSE: Bone substitutes have many applications in craniofacial surgery, yet current biomaterials remain limited. Hyperelastic bone (HB) is a composite of familiar materials, hydroxyapatite and poly-co-glycolide, with fundamentally unique physical and biocompatibility properties conferred by 3D-printing. Previously shown to induce osteogenic differentiation in vitro, this study aimed to characterize the osteoregenerative capacity of HB in a rat critical sized calvarial defect.
METHODS: Hyperelastic bone scaffolds comprised of 90%vol hydroxyapatite and 10%vol PLG and porous “fluffy” PLGA (f-PLGA) scaffolds were fabricated by direct ink writing (200-micron nozzle, 250-micron spacing, 120-degree offset). The 8-mm diameter by 0.6-mm scaffolds were implanted into 8-mm diameter critical sized calvarial defects in rats. Controls included an empty defect and replacement of the autologous bone disc. The animals were sacrificed with Microfil infusion at 8 and 12 weeks postoperatively. Skulls were analyzed by histology and micro-computed tomography (micro-CT).
RESULTS: Negative controls showed incomplete healing at 8 and 12 weeks. Positive autologous bone controls showed interdigitating bone processes at defect margins at 8 and 12 weeks. Hydroxyapatite-free f-PLGA scaffolds healed primarily with fibrous tissue and membranous cellular components within the scaffold at both timepoints. HB scaffolds contained fibrous tissue and membranous cellular components within the scaffold at 8 weeks and new bone formation at the defect margins at 12 weeks (Figure). Mineralized bone matrix was visualized by micro-CT.
CONCLUSION: HB is capable of inducing bone formation in vivo in rats without the addition of exogenous growth factors or cells. 3D-printed hyperelastic bone has the potential to be a customizable, inexpensive, osteoconductive bone substitute.


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