3D-printed polymeric scaffolds with optimized architecture to repair a sheep metatarsal critical-size bone defect

The reconstruction of critical-size bone defects in long bones remains a challenge for clinicians. We developed a new bioactive medical device for long bone repair by combining a 3D-printed architectured cylindrical scaffold made of clinical-grade polylactic acid (PLA) with a polyelectrolyte film coating delivering the osteogenic bone morphogenetic protein 2 (BMP-2). This film-coated scaffold was used to repair a sheep metatarsal 25-mm long critical-size bone defect. In vitro and in vivo biocompatibility of the film-coated PLA material were proved according to ISO standards. Scaffold geometry was found to influence BMP-2 incorporation. Bone regeneration was followed using X-ray scans, µCT scans, and histology. We showed that scaffold internal geometry, notably pore shape, influenced bone regeneration, which was homogenous longitudinally. Scaffolds with cubic pores of ∼870 µm and a low BMP-2 dose of ∼120 µg/cm 3 induced the best bone regeneration without any adverse effects. The visual score given by clinicians during animal follow-up was found to be an easy way to predict bone regeneration. This work opens perspectives for a clinical application in personalized bone regeneration.