The ASTM standard (F-code) for medical use in the U.S. is equivalent to the world standard, and in Europe, the ISO standard and the ASTM standard are being organized and merged into the European standard. In Japan, we are organizing our domestic standards, and we are organizing the standards corresponding to ASTM and ISO, and we are starting to make standards based on the ISO standards.
The titanium materials specified in the ASTM standard for implantation and placement of artificial knee joints, hip joints (including femoral heads), etc. are listed in Table 1 according to their shapes, and pure titanium and Ti-6AI-4V alloys, including powder materials, have long been used to make various shapes of components and parts.
Titanium has been used in a large number of parts such as artificial femoral joints, artificial knee joints, and bone splints, and is also used in orthopedic surgery. Patients suffering from Rheumatism (pronounced as "Reumatism", which means severe pain in the joints and muscles, and also an allergic disease), which causes severe pain and difficulty in walking, are treated with artificial femoral joints, artificial knee joints, and artificial knee joints. Patients suffering from this condition are given artificial femoral joints and artificial knee replacements, which can completely eliminate the pain and allow them to walk. In Japan, 80,000 femoral joint replacements and 40,000 knee replacements are performed in a single year (2005 statistics). In the future, with the aging of society, it is expected that the demand for artificial joints will increase by a large percentage.
Titanium is not suitable for all artificial joint parts. In the joint part, titanium is not suitable for the part that oscillates a lot because it wears out easily (ceramic and cobalt alloys are preferred), and titanium alloys are used for implanted parts. The surface of the titanium alloy is unevened and coated with a bone-sensitive material such as apatite or bioglass in order to make it bond with the biological bone at an early stage. In addition, for fracture fixation, titanium alloy intramedullary nails and titanium alloy plates are used, and various examples for implantation and attachment are shown in Figure 3.
Similarly, there is an increasing trend in the field of dentistry, where implants and attachments are being used. Titanium is used in smaller quantities, and there are pure titanium, titanium alloys, and TiNi shape memory alloys, and the shapes of these parts include the plate type shown in Fig. 4, the threaded type, the socket type, and the basket type. These parts are driven directly into the jaw bone and coated with apatite, which is representative of the composition of the bone, to be fixed in the gingival portion of the implant. Titanium is suitable for metal implants in general dentistry. There are two methods, the precision casting method and the superplastic molding method, and it is lighter in weight and does not taste bad to acidic foods compared to the previous cobalt and chromium alloys, but since the use of titanium is not covered by the health insurance diagnosis and treatment, the price is more expensive.
As an implantable accessory for internal medicine, when a patient suffers from a low heart rate, it is possible to implant a pacemaker (Pacemaker ---- is an automatic ventricular contraction device that stimulates the heart and ensures that the heart beats normally. Pacemaker Recently, pacemakers have been developed in a compact size of 20g in mass and 6mm in thickness, and they are connected with electrode wires and buried under the skin. Batteries and control circuits are contained in a small container (locket) made of pure titanium, which is non-invasive to living organisms. The battery has to last at least 6 years, so the container (locket) is required to be stable and safe for a long time. Currently, nearly 5,000 people in Japan have been benefited.
Titanium is also used in surgical instruments. Especially in the case of long brain and neurosurgery operations lasting more than 10 hours, a forceps is required to be lightweight, and titanium products are used for hemostatic forceps. Titanium is also used in many dental treatment instruments such as implants, surgical instruments for attachments, and vibrators for removing tartar. In addition to implantation (embedding) and attachment, such as auxiliary equipment and wheelchairs, titanium is also being used. When a part of a limb is missing due to an illness or accident, a prosthesis is made to restore function, and since the main part of the prosthesis is made of metal, it is being used for lightweighting, durability (mainly corrosion and fatigue resistance), and compatibility with living organisms (Ni, Cr, etc.). In the case of wheelchairs, the main goal is to lighten the entire wheelchair, so in some cases titanium is used for almost all metal parts in the structure, such as the frame and wheels.
