Additively Manufactured Porous Titanium Scaffolds for Orthopedic Implants: Design, Mechanical Behavior, and Osseointegration

Abstract

Additive manufacturing (AM) has emerged as a transformative route for fabricating porous titanium scaffolds with patient-specific geometries and bone-mimicking mechanical responses. By controlling unit-cell architecture, porosity, and surface topography, AM-fabricated Ti and Ti-6Al-4V scaffolds can simultaneously address two long-standing challenges of conventional bulk implants: stress shielding caused by stiffness mismatch between the implant and host bone, and limited osseointegration due to bioinert surfaces. This review synthesizes a decade of progress in laser powder-bed fusion (LPBF), electron-beam melting (EBM), and direct energy deposition (DED) of porous Ti structures for orthopedic applications. The mechanical behavior of strut-based and triply periodic minimal surface (TPMS) lattices is analyzed within the Gibson-Ashby framework, and the role of pore size, porosity, and surface roughness in modulating osseointegration is critically examined, with particular attention to the persistent variance in reported "optimal" pore size (≈178 µm to ≈600 µm) across the literature. Surface modification strategies, defect populations, post-processing routes, and clinical case evidence are discussed, followed by an outlook on β-Ti alloys, biodegradable metals, machine-learning-driven design, and regulatory pathways. The review is intended as a consolidated reference for researchers and clinicians working at the intersection of mechanical engineering, materials science, and orthopedic surgery.