Biomedical titanium alloy materials and their applications
Abstract: with the rapid development of biotechnology and major breakthroughs, the demand for biomedical titanium alloy is growing rapidly.However, because of the pathogenicity of V and Al elements in TC4, TC4ELI and other medical titanium alloys that have been widely used, the research and development of new medical titanium alloys has great practical significance and broad market prospects in China.The classification, basic properties and application basis of biomedical titanium alloys are described in this paper.The trend of its development in medical field is pointed out.The basic processing and preparation methods and performance evaluation methods of the new titanium alloy are also reviewed.
Biomedical titanium alloy material is a kind of functional structure material used in biomedical engineering, which is used in the production and manufacturing of surgical implants and orthopedic instruments.The production and preparation of titanium alloy processing materials involves metallurgy, pressure processing, composite materials and chemical industry, etc.Titanium and titanium alloy began to aerospace, aviation, national defense and military industries gradually entered the field of civil consumption.Implants in the health care industry, medical devices;Sports leisure industry titanium golf clubs and titanium glasses frame, titanium watches, titanium bicycles and other products, titanium processing material demand is increasing.With the vigorous development of biotechnology and major breakthroughs, the biomedical metal materials and products industry will develop into a pillar industry of the world economy.Among them, titanium and its alloy with light weight, low elastic modulus, non-toxic and non-magnetic, corrosion resistance, high strength, good toughness and other excellent comprehensive performance, in recent years, the demand has also appeared a rapid and steady growth.At the same time, as titanium alloy began to enter the field of plastic surgery, new potential market demand, titanium alloy market will appear in the future more rapid growth.
1. Research progress of medical titanium alloy
1.1 classification of medical titanium alloys
Titanium alloys can be classified into three types according to the microstructure of materials: alpha, alpha + beta and beta titanium alloys.
1.2 development trend of medical titanium alloy
It has been found that relevant research scholars at home and abroad agree that the development of medical titanium alloy has gone through three iconic stages. The first stage is represented by pure titanium and ti-6 al-4v alloy.The second stage is a new type of a-beta alloy represented by ti-5a1-2.5 Fe and ti-6a1-7nb.The third stage is mainly to develop and develop titanium beta alloys with better biocompatibility and lower elastic modulus.Ideal biomedical titanium alloy materials must meet the following conditions: good biocompatibility, low modulus of elasticity, low density, good anti-corrosion performance, non-toxic, high yield strength, long fatigue life, at room temperature has a large plastic, easy to form, easy to cast.At present, ti-6a1-4v and ti-6a1-4veli are important alloys widely used in implant materials.It has been reported in some literatures that element V can cause malignant tissue reaction, which may produce toxic and side effects on human body, while Al can cause osteoporosis, mental disorders and other diseases.In order to solve this problem, currently biomaterials scientists are committed to the exploration and research of new biomedical titanium alloy materials without V and Al. Before this, it is necessary to figure out what alloy elements are suitable for addition, non-toxic and biocompatible.It has been found that non-toxic elements such as molybdenum, niobium, tantalum and zirconium in beta titanium alloy contain higher content of beta stable elements. Compared with alpha + beta titanium alloy, it has lower elastic modulus (E=55~80GPa), better shear performance and toughness, and is more suitable for implantation into human body.
2. Application of titanium alloy
2.1 medical basis of titanium alloy
The advantages of using titanium and titanium alloy as human implants are as follows :(1) density (20℃)=4.5g/cm3, light weight.Implant into the human body: reduce the load of the human body, as a medical device: reduce the operating load of medical personnel.(2) low elastic modulus, pure titanium is 108500MPa, implanted into the human body: it is closer to the natural bone of the human body, which is conducive to bone bonding and reduces the stress shielding effect of bone on the implant.(3) non-magnetic, not affected by electromagnetic field and thunderstorm weather, conducive to the safety of the human body after use.(4) non-toxic, non-toxic side effect to human body as an implant.(5) corrosion resistance (bioinert metal materials). It has excellent corrosion resistance in the immersion environment of human blood to ensure good compatibility with human blood and cell tissues. As an implant, it will not cause human pollution and no allergic reaction.(6) high strength, good toughness, due to factors such as trauma, tumor, lead to damage of bone and joint, to build a solid bone scaffold, must with the aid of curved plates, screws, artificial bone and joint, etc., these implants will leave the body for a long time, will be affected by the bending and torsion of the human body, extrusion, the action such as muscle contraction force, require implants with high strength and toughness.
2.2 medical and orthopedic fields of titanium alloy
With the development of titanium alloy, the increase of titanium variety and the decrease of price, the application of titanium in civil industry has doubled.CFDA classifies medical devices into three levels from high to low in terms of their safety, which are respectively supervised and managed by three levels of government. Titanium and titanium alloy implants belong to the third category of medical devices and are classified as high value consumables.The sub-industries with over 5% market share include in vitro diagnosis, heart, imaging diagnosis, 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 alloys went through three iconic stages: in the early 1950s, commercial pure titanium was first used in the United Kingdom and the United States to make bone plates, screws, intramedullary nails and hips.Mathys also USES ti-6a1-7nb alloy to manufacture non-reamed intramedullary locking nail systems (including tibia, humerus, femur) and hollow screws for the treatment of femoral neck fractures.Cage made of porous ni-ti alloy (PNT) for the treatment of orthopedic spinal injuries. Canadian BIORTHEX company has developed a patent material, ACTIPORE, which is made of porous ni-ti alloy.The new titanium alloy can take into account the orthopedic, dental and vascular intervention and other advanced materials for a variety of purposes orthopedic medical devices industry accounts for 9% of the global market share of medical devices, and is still in rapid growth.The orthopedic medical device market is primarily divided into four segments: trauma, joint, spine and others.Among them, trauma is the only market segment that has not been occupied by foreign companies at present. The main reason is that the products in this field have low technical content, easy to be copied and less difficult to operate. Many secondary and tertiary hospitals can carry out trauma, and foreign companies cannot comprehensively cover it.Trauma products can be divided into internal fixation and external fixation devices. Internal fixation trauma products include intramedullary nails, bone plates and screws, etc. In 2012, trauma accounted for 34%, joint 28%, spine 20% and other 18% in the domestic orthopedic market.Big joint belongs to high-end medical devices with high technical barriers. Currently, the selection of orthopedic materials in mainstream hospitals is mainly imported. In terms of technology, design, research and development, materials and surface treatment technology, there is still a gap between domestic and imported products.Artificial joints are mainly divided into artificial knee, hip, elbow, shoulder, finger and toe joints, etc., among which the most important joint replacements include hip and knee joints, accounting for more than 95% of the global joint replacement market.Spinal implant devices include thoracolumbar board system, cervical board system and fusion cage system, among which intervertebral fusion cage system is mainly used for the treatment of disc replacement and is also the most important segment, accounting for about half of the entire spinal implant market.
3. The conclusion
The superior properties of titanium alloy make it the leading position in medical field.The material design and preparation technology of titanium alloy have been developed rapidly with the breakthrough of biotechnology and the demand of medical application.The main medical titanium alloys produced at present are alpha + beta titanium alloys.In terms of preparation technology, TC4(TC4ELI) occupies the main market share.Due to its advantages in biocompatibility and mechanical compatibility, titanium alloy beta has become a research hotspot of new medical titanium alloy and is the most promising technology in the field of medical implants.In the future, the production technology of titanium alloy should develop towards the direction of low modulus, high strength, good biocompatibility and mechanical compatibility.From the development trend, titanium alloy beta will become the future development direction and the mainstream of medical titanium alloy market.