3D-printed modular and assemblable scaffold systems: A new paradigm for patient-specific bone regeneration.

Critical-sized bone defects present a major clinical challenge, with current treatment options remaining limited in their ability to fully regenerate complex anatomical geometries. Three-dimensional printing technologies have revolutionized scaffold design and fabrication, yet conventional monolithic approaches face inherent limitations in tailoring mechanical properties, biological functionality, and surgical ease of use. Modular and assemblable scaffold systems represent an emerging paradigm that overcomes these constraints by enabling patient-specific customization, hierarchical multi-material integration, and intraoperative assembly. This review synthesizes recent advances in design principles, materials selection, fabrication technologies, and biological functionalization of modular scaffold systems for bone regeneration. We examine interlocking and snap-fit mechanisms, building-block geometries including triply periodic minimal surface (TPMS) structures, scalability across length scales, and integration of growth factor delivery and cell-laden modules. Preclinical studies suggest that modular scaffolds can offer patient-specific fit, multi-material integration, reduced stress shielding, and improved ease of surgical handling, though direct head-to-head efficacy data versus monolithic controls remain limited. Translational challenges-including manufacturing consistency, regulatory classification and clinical standardization-are discussed alongside emerging solutions through advanced printing. We conclude that modular assemblable systems represent a transformative approach to patient-specific bone regeneration, with the potential to substantially improve clinical outcomes in orthopedic and craniofacial reconstruction.