Additively manufactured metallic biomaterials for load-bearing implants: process–microstructure–property–performance–translation relationships and barriers to clinical adoption

Additive manufacturing (AM) has become the principal route to patient-specific, architected metallic implants, yet the evidence linking AM process conditions to clinical performance remains fragmented across alloy systems. This review concentrates on the three metallic systems that dominate additively manufactured load-bearing implants, namely titanium alloys (principally Ti-6Al-4 V), cobalt–chromium–molybdenum alloys, and 316L stainless steel, and organises the evidence through a Process–Microstructure–Property–Performance–Translation (PMPPT) framework that is applied operationally to each system rather than stated as a general principle. Drawing on a bibliometric mapping of the Scopus and Web of Science literature, the review establishes the selection criteria and clinical positioning of the principal alloys, treats ceramic, polymeric, and composite materials only as comparative context, and examines the metal AM routes of practical relevance: laser powder bed fusion, electron beam melting, directed energy deposition, and sinter-based processes. For each principal alloy, the review traces how cooling rate, energy density, and post-processing govern phase constitution, defect population, residual stress, and anisotropy; how these features set the strength, ductility, modulus, fatigue, corrosion, and wear envelope; and how that envelope determines osseointegration, durability, and regulatory qualification. A cross-material synthesis identifies the rate-limiting link in the PMPPT chain of each system: surface- and defect-controlled fatigue and modulus-driven stress shielding for titanium, segregation-dependent ion release and fretting corrosion for cobalt–chromium, and corrosion-limited permanence for 316L. Reproducibility of lattice architectures, post-processing standardisation, feedstock control, and the absence of long-term clinical registries emerge as the shared barriers to translation, and the developments most likely to relieve them are identified.