The excellent mechanical properties, machinability and reliability of biomedical metal materials have been widely used in clinical medicine, and their importance is equal to that of biomedical polymer materials, accounting for about 45% in the whole application of biomedical materials.
In the clinical application of metal medical materials, the main problem is still biocompatibility, due to metal corrosion and wear. Because metal materials contain more alloying elements, corrosion and wear will lead to metal ion dissolution, and then trigger some biological reactions of cell and tissue fluid, such as tissue reaction, blood reaction and systemic reaction, manifested as edema, thromboembolism, infection and tumor.
Such environment will produce corrosion on metal materials, and the corrosion products may be ions, oxides, chlorides, etc., which contact with neighboring tissues, or even penetrate into normal tissues or the whole biological system, have an impact on and stimulate normal tissues to cause abnormal growth, distortion, allergy, inflammation, infection and other adverse biological reactions, and even induce cancer. The mechanical properties of materials are attenuated by corrosion, and these two processes alone or in concert often cause material failure. Therefore, as a biomedical metal material, first of all, two basic conditions must be met: the first is non-toxic; The second is physiological corrosion resistance.
After implantation of biomedical metal materials into the human body, it is generally hoped that they can play physiological functions permanently or semi-permanently in the body. The so-called semi-permanent metal artificial joints should be at least more than 15 years. In such a long time, more or less ions or atoms on the metal surface will enter the surrounding biological tissues due to corrosion or wear. Whether the material is toxic to biological tissue becomes a necessary condition for selecting the material.
At present, medical metal materials commonly used in clinical applications mainly include stainless steel, cobalt alloy, titanium alloy, shape memory alloy, precious metals and pure metal tantalum, niobium, zirconium, etc. The properties of these materials in the application process are as follows.
