Recent Advances in Metal and Metal Alloy–Based Orthopedic Implants: Processing Strategies, Clinical Challenges, and Future Perspectives

Abstract

Orthopedic implants are essential in the restoration of skeletal functions lost through trauma, disease, or congenital abnormalities. Specifically, among biomaterials, metals and metal alloys are the most prominent and popular choice for bearing-loading implants based on their strength, fracture work-of-compliance, wear properties, and long-term utilization in the body. Traditionally, stainless steel, cobalt-chromium alloys, and titanium alloys have been prominent due to their strength and durability under physiological stresses, as well as their anticorrosion properties in biological fluids. Interestingly, recent innovations in metallurgical processing and surface modification have significantly enhanced the performance capabilities and durability of life spans. Processing methods, such as powder metallurgy and rapid prototyping, provide microstructural and geometric designs for implants, while surface modification methods improve efforts directed at enhancement via impedance integration. However, current long-term clinical capabilities are hampered by limitations such as stress-protected implants, ion toxicity, wear-away properties, and reduced impedance bonding. In recent years, emerging innovations such as alloying with biocompatible elements (e.g., Niobium, Zirconium, and Molybdenum) and nanoscale surface modifications have attracted increasing attention, highlighting the need for a comprehensive evaluation of next-generation metallic biomaterials for orthopedic applications. This review gives a comprehensive analysis of recent metallic implants, highlights their mechanical properties, biocompatibility, and surface modification strategies. Furthermore, it also touches existing challenges during processing and clinical application and emphasizes future research directions for next-generation orthopedic implant materials.