Among them, titanium and its alloys, by virtue of its light weight, low modulus of elasticity, non-toxic, non-magnetic, corrosion-resistant, high strength, good toughness, and other excellent comprehensive performance, the demand for titanium alloys in recent years has also seen rapid and steady growth.
As titanium alloys began to enter orthopedics and other fields, new market demands emerged. The future market for titanium alloys is expected to grow rapidly.
Medical titanium alloy research progress
1.Classification of medical titanium alloy
Titanium alloys can be divided into three categories according to the type of material microstructure: α-type, α+β-type and β-type titanium alloys; their typical properties are shown in Table 1.
Table 1 Classification and typical properties of biomedical titanium alloys
2.Development trend of medical titanium alloys
Literature research has revealed that relevant researchers and scholars agree 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 the new α+β type alloy represented by Ti5A1-2.5Fe and Ti-6A1-7Nb;
The third stage is the main development and development of better biocompatibility and lower elastic modulus β-titanium alloys.
The ideal biomedical titanium alloy material must meet the following conditions:
It has good biocompatibility and a low modulus of elasticity. It also has low density and strong anti-corrosion properties. The material is non-toxic and has high yield strength. It offers a long fatigue life and large plasticity at room temperature. Additionally, it is easy to form and cast.
The important alloys that have been widely used as implant materials are Ti-6A1-4V and Ti-6A1-4VELI.
Element V can cause malignant tissue reactions. It may have toxic effects on the human body. Aluminum (Al) can cause osteoporosis, mental disorders, and other diseases.
To address this issue, biomaterials scientists are exploring new biomedical titanium alloys without V and Al. First, they need to identify alloying elements that are both non-toxic and biocompatible.
It is found that β titanium alloys containing non-toxic elements such as molybdenum, niobium, tantalum and zirconium contain higher content of β stabilizing elements, and compared with α + β type titanium alloys, they have lower modulus of elasticity (E = 55 ~ 80 GPa) and better shear properties and toughness, which is more suitable for implantation into the human body as an implant.
Applications of Titanium Alloys
1.Medical Basis of Titanium Alloys
The main advantages of using titanium and titanium alloys as human implants are:
(1) Density (20℃)=4.5g/cm3, light weight. Implanted in the human body: to reduce the human body load, as a medical device: to reduce the operating load of medical personnel.
(2) Pure titanium has a low modulus of elasticity, about 108,500 MPa. When implanted, it closely matches human bone, supports grafting, and reduces stress shielding.
(3) Non-magnetic, not affected by electromagnetic fields and thunderstorms, which is conducive to human safety after use.
(4) Non-toxic, no toxic side effects on the human body as an implant.
(5) Corrosion resistance (bio-inert metal materials) means excellent resistance in human blood environments, ensuring good compatibility with blood and tissues. Implants do not cause contamination or allergic reactions, which is key for using titanium and its alloys.
(6) High strength and good toughness, due to trauma, tumors and other factors leading to bone and joint damage, in order to establish a solid bone scaffolding, must be used with the help of curved plates, screws, artificial bone and joints, etc., these implants should be left in the body for a long time, will be subject to the human body’s bending, twisting, extrusion, muscle contraction and other roles, the requirements of the implant has a high degree of strength and toughness.
2.Titanium alloy medical field and orthopedic field market situation
(1) Development and Application of Titanium Alloys in the Medical Industry
With the development of titanium alloys, the variety of titanium materials has expanded, and their costs have decreased, driving exponential growth in their applications within the civil industry. In the medical sector, the CFDA (China Food and Drug Administration) categorizes medical devices into three classes based on safety. Titanium and titanium alloy implants are classified as Class III medical devices, the highest risk category, and are considered high-value consumables.
Sub-industries with over 5% market share include in vitro diagnostics, cardiac interventions, diagnostic imaging, orthopedics, and ophthalmology. Among them, in vitro diagnostics, orthopedics, and cardiac interventions are currently the fastest-growing sectors in China. The application of biomedical titanium and its alloys has experienced three major historical stages:
- In the early 1950s, the UK and US began using pure titanium to make implants like screws and hip joints.
- Swiss company Mathys developed Ti-6Al-7Nb alloy for non-expandable intramedullary nailing systems and hollow screws for treating femoral neck fractures.
- Canadian company BIORTHEX introduced ACTIPORE gamma, a porous Ni-Ti alloy for manufacturing cervical and lumbar interbody fusion cages to treat spinal injuries.
New β-type titanium alloys are emerging as promising materials due to their excellent biocompatibility, mechanical compatibility, and versatility for use in orthopedics, dentistry, and vascular interventions.
(2) Orthopedic Device Market Landscape and Titanium Alloy Application
The orthopedic medical device industry accounts for approximately 9% of the global medical device market and continues to grow at a rapid pace. This market is mainly divided into four segments: trauma, joint, spine, and others.
- Trauma devices include internal and external fixation systems. Internal devices commonly consist of intramedullary nails, splints, and screws.
- Joint replacement devices are high-end products with significant technical challenges. The most prominent artificial joints are hip and knee replacements, which together represent over 95% of the global joint replacement market.
- Spinal implant systems include thoracolumbar and cervical spine nail plate systems, as well as fusion systems, with intervertebral fusion systems being the most crucial, accounting for nearly 50% of the entire spinal implant market.
With continued material innovation, especially in β-type titanium alloys, the orthopedic sector is poised for further expansion, offering advanced and more compatible solutions for various surgical and implant applications.
Conclusion
The superior performance of titanium alloy has achieved its leading position in the medical field. The material design and preparation technology of titanium alloy has been rapidly developed with the breakthrough of biotechnology and the large demand of medical applications.
The currently produced medical titanium alloys are mainly α+β type titanium alloys. From the point of view of preparation process, the production of TC4 (TC4ELI) currently occupies the main market share.
β-type titanium alloys have become the research hotspot of new medical titanium alloys due to their advantages in biocompatibility and mechanical compatibility, which is the most promising technology in the field of medical implants.
Future titanium alloy production should aim for lower modulus, higher strength, and better biocompatibility and mechanical compatibility.
β-type titanium alloys are expected to lead future development and dominate the medical titanium alloy market.