3D-printing technologies and biomaterial innovations for bone tissue engineering: current status and future...

Bone fractures and osteoporosis-related defects continue to pose major global health and socioeconomic burdens, necessitating the development of advanced regenerative approaches. This review presents a comprehensive overview of bone anatomy, fracture types, and healing mechanisms, followed by an in-depth discussion of current clinical strategies for enhancing bone regeneration, such as distraction osteogenesis, casting, splinting, and bone grafting. The limitations of these conventional treatments highlight the urgent need for innovative solutions through three-dimensional (3D) printing technologies. The review explores 3D-printed scaffolds as a transformative platform in bone tissue engineering, detailing key fabrication techniques, including stereolithography, selective laser sintering, fused deposition modeling, and bioplotter printing, and the integration of nanotechnology to enhance scaffold biofunctionality. Various biomaterial classes are critically assessed, including metal-, ceramic-, polymer-, and composite-based scaffolds, along with design parameters that govern architectural integrity, mechanical performance, and cellular responses. Emerging trends such as four-dimensional (4D) implanting, aimed at achieving dynamic, stimuli-responsive scaffolds, are also highlighted. Finally, the review discusses ongoing challenges related to vascularization, immune compatibility, mechanical optimization, scalability, and regulatory and ethical considerations. By bridging biological principles with engineering innovation, this work provides a forward-looking perspective on the design and clinical translation of next-generation bone scaffolds for improved regenerative outcomes.