Advances in surface functionalization of porous titanium as novel orthopedic implants - a review

Porous titanium (PT) and its alloys are widely used in orthopedic applications due to their interconnected porosity, favorable mechanical properties, biocompatibility, and low elastic modulus that alleviates stress shielding. However, the long-term clinical success of PT implants is largely determined by their surface characteristics. In recent years, surface functionalization has emerged as a promising strategy for tailoring the physicochemical and biological properties of PT. By constructing bioactive coatings or functional interfaces with controlled composition and microstructure, these approaches can significantly enhance corrosion and wear resistance, often reducing corrosion current density by one to two orders of magnitude. They also exhibit high antibacterial performance, commonly exceeding 90% efficacy against representative bacterial strains, and promote osteogenic responses, with cell adhesion, proliferation, and differentiation generally enhanced compared to unmodified controls, thereby facilitating osseointegration. This review systematically summarizes recent advances in PT surface functionalization, encompassing in-situ modification, coating-based, and pore-filling strategies, with a focus on their mechanisms, applications, and comparative advantages. Furthermore, emerging trends and innovative approaches are discussed, highlighting their potential for developing multifunctional and clinically translatable PT implants. Overall, this review provides an overview of recent progress and remaining challenges, offering guidance for the rational design of next-generation PT implants with enhanced biological performance and clinical applicability.