Boosting bone regeneration using augmented melt-extruded additive-manufactured scaffolds

Bone tissue engineering (BTE) is in active search of the ideal scaffold to give a clinical solution for bone regeneration in non-union fractures. During the last decades, the use of additive manufacturing (AM), and, in particular, melt extrusion AM (ME-AM), has been investigated towards this aim. ME-AM enables the fabrication of personalized 3D scaffolds, with a controlled and highly interconnected porosity, through the solvent-free processing of biodegradable and mechanically robust polymers. In addition to these properties matching the requirements for BTE scaffolds, the polymers used to fabricate these constructs are also more amenable for further functionalization than metals or ceramics, to influence cell behaviour, making thermoplastic materials a preferred choice for BTE. This review provides a comprehensive analysis of various ME-AM scaffolds developed for BTE, along with approaches used to augment their bioactivity, which includes architectural, surface physical and chemical modifications, the incorporation of secondary fibrous or hydrogel networks within the scaffold pores, and the use of composites for ME-AM scaffold fabrication.