Artificial joint material analysis: Medical implantable Metal? Polymers? Ceramics?

2. Metal Materials

Metallic materials are widely used in artificial joints because of their good mechanical properties, ease of processing and stability. The main metal materials include Stainless Steel, cobalt-based alloys, titanium alloys, and tantalum metals.

Titanium alloy


Titanium is an important structural metal developed in the 1950s. The first titanium alloy used was the Ti-6Al-4V alloy successfully developed in 1954 in the United States, which became the ace alloy in the titanium alloy industry due to its better heat resistance, strength, plasticity, toughness, formability, weldability, corrosion resistance and biocompatibility. In the 1950s, it was developed as an aero-engine and aircraft body material, and its main application in the industry is characterized by high strength, high plasticity, high toughness and high metal damage tolerance. At present, the domestic standard for Ti-6Al-4V alloy for artificial joints is YY 0117.2-2005.

Stainless steel

Stainless steel is the first material used in artificial joint prosthesis, has a certain corrosion resistance and mechanical strength, but contains elements such as Ni has a teratogenic effect, not suitable for long-term stay in the body 1, in addition, stainless steel material itself is not biologically active, it is difficult to form a stable and solid bond with bone tissue. Therefore, in the artificial joint materials, stainless steel is gradually replaced by cobalt-based alloys and titanium alloys. In recent years, the clinical use of cobalt-based alloys and titanium alloys as artificial joint prosthesis materials.

Compared with stainless steel, the passivation film of cobalt-based alloy is more stable and has better corrosion resistance. Its disadvantages mainly include the leaching of Co and Ni plasma caused by metal friction corrosion, which stimulates the secretion of cytokines 0PG and other substances2 and causes necrosis of bone cells and tissues in vivo, thus leading to complications such as loosening of the patient's joint and sinking of the joint prosthesis.

Cobalt-chromium alloy


Cobalt-chromium alloy is a hard alloy that is resistant to various types of wear and corrosion as well as high-temperature oxidation. It is commonly referred to as cobalt-chromium-tungsten (molybdenum) alloy or stearic alloy (stearic alloy was invented by American Elwood Hayness in 1907). Cobalt-based alloys are made with cobalt as the main component and contain considerable amounts of nickel, chromium, tungsten and small amounts of molybdenum, niobium, tantalum, titanium, lanthanum and other alloying elements.


Cobalt and chromium are the two basic elements of cobalt-based alloys, while the addition of molybdenum gives a finer grain and higher strength after casting or forging. Cobalt-chromium-molybdenum alloys are basically divided into two categories: one is CoCrMo alloys, which are usually cast products, and the other is CoNiCrMo alloys, which are usually (hot) forged for precision machining. Artificial joint products are commonly used as cast CoCrMo alloys, and dental related implants can also be manufactured. At present, the domestic standard for casting Cocrmo Alloy is YY 0117.3-2005.

Porous tantalum metal materials

Porous tantalum material is a new type of orthopedic implant material that has emerged recently. Because of its good histocompatibility, high porosity, high surface friction coefficient and low elastic modulus, it has been recognized as an ideal orthopedic implant material. The pore structure of porous tantalum metal is similar to that of cancellous bone trabeculae, with a three-dimensional connected pore structure, which is very suitable for the long entry of bone tissue; its elastic modulus matches the elastic modulus of bone tissue at the implantation site, avoiding the stress masking effect. Porous tantalum is chemically stable in the body fluid environment and exhibits excellent biocompatibility. The many advantages of porous tantalum metal have led to its increasing interest and widespread use in clinical applications.


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Public data shows that the Medical Device market is growing at a CAGR of 5.6% from 2018-2024 (Source: Firestone Creations). In terms of segmentation, orthopedic medical device sales are $36.5 billion, accounting for 9% of the global medical device share. How does the material selection, product design and biological evaluation of metal orthopedic implants become a pressing challenge today?

3. Ceramic Materials

In the medical field, ceramics are used as implant materials not only for artificial joints, but also for oral prosthetics. Among these, ceramic dental implants are a potential market of interest for ceramic material companies worldwide.

Ceramic materials are a new type of prosthetic material that emerged after metal and polyethylene. It is widely used because of its good biocompatibility and low wear rate. It is mainly used for acetabular lining, femoral head part or femoral condyle prosthesis. The dishes we use in life are also made of ceramic, but the ceramic material chosen for the joint prosthesis is very different from the ceramic used for dishes.

The ceramic used in life is made of clay that is sintered at high temperatures, while the ceramic used in joint prosthesis is made of high purity alumina and zirconia, and the sintering temperature is higher and more strictly controlled. Artificial hip joints, on the other hand, are divided into three categories: ceramic-ceramic, ceramic-polyethylene, and alloy-polyethylene, depending on the material of the ball head and acetabular cup. The main difference between ceramic-ceramic, ceramic-polyethylene and alloy-polyethylene is reflected in the mechanical and biological properties. Special materials and specific processes produce ceramics that are both wear-resistant and hard. The literature reports that hip prostheses made of ceramics wear only 5 microns per year, making them durable and the best choice for young patients.

Artificial joint replacement has been hailed as one of the major milestones in the history of orthopedic surgery in the 20th century, and the cornerstone of the creation and development of joint replacement lies in joint prostheses. A joint prosthesis may seem insignificant, but it is the result of the integration of science and technology in many fields such as medicine, metallurgy, materials, chemicals, and mechanics, and is the result of decades of joint efforts between orthopedic surgeons and scientists from different fields. With the development of technology, more and more excellent prosthetic materials will emerge for the benefit of patients, so that patients can get rid of joint diseases.