Porous Ti-6Al-4V Architectures in Load-Bearing Orthopedic Reconstruction: A Critical Narrative Review of the Translational Gap Across Microstructure, Fatigue, Surface Function, and Clinical Failure Modes

Abstract

An aging population and a rising revision burden are increasing demand for bone-compatible load-bearing implants. Because the elastic modulus of conventional Ti-6Al-4V (~110 GPa) exceeds that of cortical bone (7–30 GPa), stress shielding can drive bone resorption and aseptic loosening. Two solution lines have emerged: low-modulus β-type alloys and porous architectures. Focusing on additive manufacturing (AM), this critical narrative review synthesizes the evidence along the axis of clinical failure modes. Materials science has lowered β-Ti’s modulus to ~40 GPa in bulk, yet clinical implants rely predominantly on porous conventional Ti-6Al-4V: the low effective modulus (single-digit GPa) comes from architecture, not alloying. These architectures range from porous fixation surfaces on solid acetabular shells to predominantly porous constructs—revision knee cones and sleeves, acetabular augments, and spinal interbody cages. In the acetabular cohorts, where clinical evidence is concentrated, short- to mid-term survivorship is favorable though heterogeneous; revisions were driven mainly by infection and instability, with aseptic loosening low. Two tools are proposed: a synthesis matrix setting laboratory claims alongside clinical evidence for each design parameter, and a 16-item minimum reporting checklist. Applied to the 12 primary series reviewed, the checklist found manufacturing and architecture-verification parameters largely unreported even where clinical outcomes are well documented.