Biomedical titanium alloy materials and their applications

Biomedical titanium alloy materials refer to a class of functional structural materials used in biomedical engineering, specifically in the production and manufacturing of surgical implants and orthopedic instrument products. The production and preparation of titanium alloy processing materials involve metallurgy, pressure processing, composite materials, and chemical industries, and are recognized as high-tech products worldwide. Titanium and titanium alloys have gradually entered the civilian consumption field from aerospace, aviation, and defense and military industries. Implants and medical devices in the healthcare industry; The demand for titanium processed materials in sports and leisure industries, including titanium golf clubs, titanium eyeglass frames, titanium watches, titanium bicycles, and other products, is constantly increasing. With the vigorous development and major breakthroughs of biotechnology, the biomedical metal materials and their products industry will develop into a pillar industry of the world economy. Among them, titanium and its alloys have seen a rapid and steady increase in demand in recent years due to their excellent comprehensive properties such as light weight, low elastic modulus, non-toxic and non-magnetic properties, corrosion resistance, high strength, and good toughness. Meanwhile, as titanium alloys begin to enter fields such as plastic surgery, new potential market demands emerge, and the future titanium alloy market will experience even faster growth.

Research progress of medical titanium alloys

1.1 Classification of medical titanium alloys

Titanium alloys can be divided into: α Type, α+β Type and β Type 3 titanium alloys.

1.2 Development trends of medical titanium alloys

Through literature research, it was found that domestic and foreign scholars unanimously believe that the development of medical titanium alloys has gone through three iconic stages. The first stage is represented by pure titanium and Ti-6Al-4V alloy; The second stage is a new type represented by Ti-5A1-2.5Fe and Ti-6A1-7Nb α+β Type alloy; The third stage is mainly focused on the development and research of materials with better biocompatibility and lower elastic modulus β- The stage of titanium alloy. The ideal biomedical titanium alloy material must meet the following conditions: good biocompatibility, low elastic modulus, low density, good anti-corrosion performance, non-toxic, high yield strength, long fatigue life, large plasticity at room temperature, easy forming, easy casting, etc. The important alloys currently widely used in implant materials are Ti-6A1-4V and Ti-6A1-4VELI. There are literature reports that V element can cause malignant tissue reactions, which may have toxic side effects on the human body, while Al can cause diseases such as osteoporosis and mental disorders; In order to solve this problem, current biomaterialists are committed to exploring and researching new biomedical titanium alloy materials that do not contain V and Al. Before that, it is necessary to clarify what alloy elements are suitable for addition, which are non-toxic and comply with the principle of biocompatibility. A study has found that non-toxic elements such as molybdenum, niobium, tantalum, zirconium, etc β Titanium alloy contains a high content of β Stable elements, related to α+β Compared with titanium alloy, it has a lower elastic modulus (E=55~80GPa), better shear performance and toughness, and is more suitable for implantation in the human body.

Application of 2 titanium alloys

2.1 Medical Fundamentals of Titanium Alloy

The main advantages of using titanium and titanium alloys as human implants are: (1) density (20 ℃)=4.5g/cm3, lightweight. Implantation into the human body: reducing the burden on the body, as a medical device: reducing the operational load on medical personnel. (2) Low elastic modulus, pure titanium is 108500MPa, implanted in the human body: closer to the natural bone of the human body, conducive to bone grafting, reducing the stress shielding effect of the bone on the implant. (3) Non magnetic, unaffected by electromagnetic fields and thunderstorms, beneficial for human safety after use. (4) Non toxic, as an implant, it has no toxic side effects on the human body. (5) Corrosion resistance (bio inert metal materials), with excellent corrosion resistance in the immersion environment of human blood, ensuring good compatibility with human blood and cellular tissues. As an implant, it does not produce human contamination and does not cause allergic reactions. This is the basic condition for the application of titanium and titanium alloys. (6) High strength, good toughness, and damage to bones and joints due to trauma, tumors, and other factors. In order to establish a stable bone scaffold, it is necessary to use curved plates, screws, artificial bones, and joints. These implants must be left in the human body for a long time and will be subjected to bending, twisting, compression, muscle contraction, and other effects, requiring the implants to have high strength and toughness.

2.2 The medical and orthopedic fields of titanium alloys

With the development and research of titanium alloys, the increase in titanium material varieties, and the decrease in prices, the application of titanium in civil industry has doubled. The CFDA categorizes medical devices into three levels based on their safety, from highest to lowest, and is supervised and managed by the third level government. Implants made of titanium and titanium alloy materials belong to the third category of medical devices and are classified as high-value consumables. The sub industries that account for over 5% of the segmented market include in vitro diagnostics, cardiology, imaging diagnostics, orthopedics, ophthalmology, and plastic surgery. Among them, in vitro diagnosis, orthopedics, and cardiac intervention are the fastest-growing high-value consumables in China. The application of biomedical titanium and its alloy materials has gone through three iconic stages: in the early 1950s, commercial pure titanium was first used in the UK and the US to manufacture bone plates, screws, intramedullary nails, and hip joints. Swiss company Mathys also uses Ti-6A1-7Nb alloy to manufacture non expanding intramedullary nail systems (including tibia, humerus, femur) and hollow screws for the treatment of femoral neck fractures. Porous Ni Ti (PNT) alloy bioactive material is used to manufacture cervical and lumbar interbody fusion cages (Cage). BIORTHEX, a Canadian company, has developed a patented porous Ni Ti alloy material, ACTIVE, for the treatment of orthopedic spinal injuries. new type β Titanium alloy is an advanced material that can serve multiple purposes such as orthopedics, dentistry, and vascular intervention. The orthopedic medical device industry accounts for 9% of the global medical device market share and is still growing rapidly. The orthopedic medical device market is mainly divided into four areas: trauma, joints, spine, and others. Among them, trauma is currently the only segmented field that has not been dominated by foreign enterprises in terms of market share. The main reason is that the product technology in this field is relatively low, easy to replicate, and the difficulty of surgery is relatively small. Many second and third level hospitals can carry out this, and foreign enterprises cannot fully cover it. Trauma products can be divided into internal fixation and external fixation instruments. Internal fixation trauma products include intramedullary nails, bone plates, and screws. In 2012, trauma accounted for 34% of the domestic orthopedic market, joints accounted for 28%, spine accounted for 20%, and others accounted for 18%. The large joint belongs to high-end medical devices with high technological barriers. Currently, mainstream hospitals mainly choose imported orthopedic materials. There is still a gap between domestic and imported products in terms of technology, design, research and development, materials, and surface treatment processes. Artificial joints are mainly divided into knee, hip, elbow, shoulder, finger, toe joints, etc. Among them, the most important joint replacements include hip and knee joints, totaling over 95% of the global joint replacement market. Spinal implant instruments include thoracolumbar spine nail plate systems, cervical spine nail plate systems, and fusion cage systems, among which the intervertebral fusion cage system is mainly used for the treatment of intervertebral disc replacement and is also the most important sub field, accounting for about half of the entire spinal implant market.

3 Conclusion

The superior performance of titanium alloy has led to its leading position in the medical field. The material design and preparation technology of titanium alloys has rapidly developed with the breakthroughs in biotechnology and the high demand for medical applications. The main medical titanium alloys currently produced are α+β Type titanium alloy. From the perspective of preparation technology, the production of TC4 (TC4ELI) currently occupies the main market share. β Due to its advantages in biocompatibility and mechanical compatibility, type titanium alloys have become a research hotspot for new medical titanium alloys and the most promising technology in the field of medical implants. In the future, the production technology of titanium alloys should develop towards low modulus, high strength, good biocompatibility, and mechanical compatibility. From the perspective of development trends, β Type titanium alloys will become the direction of future development and the mainstream of the medical titanium alloy market.