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Titanium alloys have emerged as the most successful metallic material to ever be applied in the field of biomedical engineering. This comprehensive review covers the history of titanium in medicine, the properties of titanium and its alloys, the production technologies used to produce biomedical implants, and the most common uses for titanium and its alloys, ranging from orthopedic implants to dental prosthetics and cardiovascular devices. At the core of this success lies the combination of machinability, mechanical strength, biocompatibility, and corrosion resistance. This unique combination of useful traits has positioned titanium alloys as an indispensable material for biomedical engineering applications, enabling safer, more durable, and more efficient treatments for patients affected by various kinds of pathologies. This review takes an in-depth journey into the inherent properties that define titanium alloys and which of them are advantageous for biomedical use. It explores their production techniques and the fabrication methodologies that are utilized to machine them into their final shape. The biomedical applications of titanium alloys are then categorized and described in detail, focusing on which specific advantages titanium alloys are present when compared to other materials. This review not only captures the current state of the art, but also explores the future possibilities and limitations of titanium alloys applied in the biomedical field.

Metal implants are widely used in the treatment of orthopedic diseases. However, owing to the mismatched elastic modulus of the bone and implants, stress shielding often occurs clinically which can result in failure of the implant or fractures around the implant. Topology optimization (TO) is a technique that can provide more efficient material distribution according to the objective function under the special load and boundary conditions. Several researchers have paid close attention to TO for optimal design of orthopedic implants. Thanks to the development of additive manufacturing (AM), the complex structure of the TO design can be fabricated. This article mainly focuses on the current stage of TO technique with respect to the global layout and hierarchical structure in orthopedic implants. In each aspect, diverse implants in different orthopedic fields related to TO design are discussed. The characteristics of implants, methods of TO, validation methods of the newly designed implants, and limitations of current research have been summarized. The review concludes with future challenges and directions for research.

A major advantage of additive manufacturing (AM) technologies is the ability to print customized products, which makes these technologies well suited for the orthopedic implants industry. Another advantage is the design freedom provided by AM technologies to enhance the performance of orthopedic implants. This paper presents a state-of-the-art overview of the use of AM technologies to produce orthopedic implants from lattice structures and functionally graded materials. It discusses how both techniques can improve the implants’ performance significantly, from a mechanical and biological point of view. The characterization of lattice structures and the most recent finite element analysis models are explored. Additionally, recent case studies that use functionally graded materials in biomedical implants are surveyed. Finally, this paper reviews the challenges faced by these two applications and suggests future research directions required to improve their use in orthopedic implants.

Metals have been used for orthopedic implants for a long time due to their excellent mechanical properties. With the rapid development of additive manufacturing (AM) technology, studying customized implants with complex microstructures for patients has become a trend of various bone defect repair. A superior customized implant should have good biocompatibility and mechanical properties matching the defect bone. To meet the performance requirements of implants, this paper introduces the biomedical metallic materials currently applied to orthopedic implants from the design to manufacture, elaborates the structure design and surface modification of the orthopedic implant. By selecting the appropriate implant material and processing method, optimizing the implant structure and modifying the surface can ensure the performance requirements of the implant. Finally, this paper discusses the future development trend of the orthopedic implant.

Orthopaedic implants have significantly improved the treatment of musculoskeletal injuries and degenerative diseases, restoring function and alleviating pain. However, long-term implant success remains challenging due to loosening, wear, and infections. Recent advancements in materials science, bioengineering, and digital technologies are driving innovations in orthopaedic implants, enhancing their performance and patient outcomes. New biomaterials, such as advanced metal alloys, polymers, ceramics, and nanocomposites, offer superior biocompatibility and mechanical durability, minimizing adverse reactions. Additive manufacturing (3D printing) allows the creation of patient-specific implants with porous architectures closely resembling natural bone, enhancing osseointegration. Additionally, surface engineering techniques, including bioactive coatings for improved bone bonding and antimicrobial layers for infection prevention, address persistent issues at the implant-tissue interface. The emergence of “smart” implants equipped with sensors and wireless connectivity enables real-time monitoring of biomechanical parameters, paving the way for personalized, data-driven orthopaedic care. This review summarizes significant developments in orthopaedic implant technology from 2020 to 2025, highlighting advances in materials, design, and functionality. We discuss how these innovations address traditional challenges and examine remaining hurdles to clinical application. Future directions, such as biodegradable implants that eliminate secondary surgeries and AI-assisted implant design, are also explored. Collectively, these breakthroughs promise a new era in orthopaedic treatments, marked by enhanced implant longevity, functionality, and patient quality of life.

Additive manufacturing has been used to develop a variety of scaffold designs for clinical and industrial applications. Mechanical properties (i.e., compression, tension, bending, and torsion response) of these scaffolds are significantly important for load-bearing orthopaedic implants. In this study, we designed and additively manufactured porous metallic biomaterials based on two different types of triply periodic minimal surface structures (i.e., gyroid and diamond) that mimic the mechanical properties of bone, such as porosity, stiffness, and strength. Physical and mechanical properties, including compressive, tensile, bending, and torsional stiffness and strength of the developed scaffolds, were then characterised experimentally and numerically using finite element method. Sheet thickness was constant at 300 μm, and the unit cell size was varied to generate different pore sizes and porosities. Gyroid scaffolds had a pore size in the range of 600–1200 μm and a porosity in the range of 54–72%, respectively. Corresponding values for the diamond were 900–1500 μm and 56–70%. Both structure types were validated experimentally, and a wide range of mechanical properties (including stiffness and yield strength) were predicted using the finite element method. The stiffness and strength of both structures are comparable to that of cortical bone, hence reducing the risks of scaffold failure. The results demonstrate that the developed scaffolds mimic the physical and mechanical properties of cortical bone and can be suitable for bone replacement and orthopaedic implants. However, an optimal design should be chosen based on specific performance requirements.

Prosthesis-associated infections are one of the main causes of implant failure; thus it is important to enhance the long-term antibacterial ability of orthopedic implants. Titanium dioxide nanotubes (TNTs) are biomaterials with good physicochemical properties and biocompatibility. Owing to their inherent antibacterial and drug-loading ability, the antibacterial application of TNTs has received increasing attention. In this review, the process of TNT anodizing fabrication is summarized. Also, the mechanism and the influencing factors of the antibacterial property of bare TNTs are explored. Furthermore, different antibacterial strategies for carrying drugs, as well as modifications to prolong the antibacterial effect and reduce drug-related toxicity are discussed. In addition, antibacterial systems based on TNTs that can automatically respond to infection are introduced. Finally, the currently faced problems are reviewed and potential solutions are proposed. This review provides new insight on TNT fabrication and summarizes the most advanced antibacterial strategies involving TNTs for the enhancement of long-term antibacterial ability and reduction of toxicity. Keywords: antibacterial property, drug delivery, titanium dioxide nanotube, orthopedic implant, surface modification

Enoxaparin sodium (ES), a low molecular weight heparin derivative, has recently been recognized for its diverse biological activities. In particular, the ability of heparin to modulate inflammation has been utilized to enhance the biocompatibility of bone implant materials. In this study, we utilized poly (methyl methacrylate) (PMMA), a drug loading bone implant material, as a matrix and combined this with enoxaparin sodium (ES) to create enoxaparin sodium PMMA cement (ES-PMMA) to investigate the regulatory effects of ES on inflammatory responses in bone tissue from an animal model. We established a rabbit model of femoral condyle bone defects to investigate the immunoregulatory mechanisms of ES-PMMA. Rabbits were divided into control (n = 5), model (n = 10), PMMA (n = 10) and ES-PMMA (n = 10) groups. The control group underwent sham surgery as a blank control, while the model group was established with a bone defect model in the rabbit femoral condyle. The PMMA group and ES-PMMA group followed the same modeling procedure as the model group. After successful modeling, the PMMA group and ES-PMMA group were implanted with PMMA bone cement columns and ES-PMMA bone cement columns, respectively. Ten days post-surgery, cancellous bone tissue from the defect site was collected from each group, and the control group was sampled at the same location. Tissue samples were collected from each group for transcriptomic sequencing. RNA sequencing (RNA-seq) was performed and differentially expressed mRNAs were identified between the model and controls, between the PMMA and model groups, and between the ES-PMMA and model groups. Key candidate genes associated with ES-PMMA treatment were identified (304 genes), and Gene Set Variation Analysis (GSVA), Gene Ontology (GO), and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analyses were performed on the differentially expressed genes and key candidate genes in each group (P < 0.05). The 304 key candidate genes associated with ES-PMMA treatment are involved in functions such as inflammation, cell proliferation, and differentiation. Protein-protein interaction (PPI) network analysis and machine learning revealed three key candidate genes in the ES-PMMA group: recombination activating gene ( RAG1 ), Src-like adaptor 2 ( SLA2 ), S100 calcium binding protein and beta (neural) ( S100B ). SLA2 and RAG1 are known to be related to inflammation, whereas S100B is related to osteogenic differentiation. Finally, the subcellular localization and functional similarities of the three genes were assessed, and their transcription factors and miRNAs were predicted. Collectively, these findings provide insights into the mechanism of ES in regulating immune responses in the bone; this may facilitate the development of novel bone implant materials.

Metal additive manufacturing (metal-AM) technology has made significant progress in the field of biomedicine in recent years. Originally, it was only used as an innovative resource for prototypes. With the development of technology, custom orthopedic implants could be produced for different patients. Titanium alloy is non-toxic and harmless in the human body. It has excellent biocompatibility and can promote the growth and regeneration of bones in its interior. Therefore, it is widely used in the medical industry. However, in the process of additive manufacturing and printing titanium alloys, there are often cases where the powder is not completely melted or the powder adheres to the product structure after printing, which introduces new biological risks. This paper summarizes the causes of powder adhesion from the perspective of the process involved in additive manufacturing, expounds the influence of different processes on the powder adhesion of titanium alloy forming parts, introduces the mainstream methods of powder sticking removal and summarizes the application of the additive manufacturing of titanium alloy in the medical field, which provides a theoretical basis for further development of the application of titanium alloy additive manufacturing technology in the medical industry.

Implant material is a more important factor for periprosthetic tibial bone resorption than implant design after total knee arthroplasty (TKA). The virtual perturbation study was planned to perform using single case of proximal tibia model. We determined whether the implant materials' stiffness affects the degree of periprosthetic tibial bone resorption, and whether the effect of material change with the same implant design differed according to the proximal tibial plateau areas. This three-dimensional finite element analysis included two cobalt-chromium (CoCr) and two titanium (Ti) tibial implants with different designs. They were implanted into the proximal tibial model reconstructed using extracted images from computed tomography. The degree of bone resorption or formation was measured using the strain energy density after applying axial load. The same analysis was performed after exchanging the materials while maintaining the design of each implant. The degree of periprosthetic tibial bone resorption was not determined by the type of implant materials alone. When the implant materials were changed from Ti to CoCr, the bone resorption in the medial compartment increased and vice versa. The effect of material composition's change on anterior and posterior areas varied accordingly. Although the degree of bone resorption was associated with implant materials, it differed depending on the design of each implant. The effect on the degree of bone resorption according to the materials after TKA should be evaluated while concomitantly considering design.