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Historical Perspective of Metallic Implants

The earliest written record of an application of metal in surgical procedure is from the year 1565. However, until Lister’s aseptic surgical technique was developed in the 1860s, various metal devices such as wires and pins which were constructed of iron, gold, silver, platinum, etc., and tissue transplantations were not largely successful mainly due to infection after implantation. The use of alloys in surgical implants is a relatively modern development, dating back about a century (reference). Early steel formulations were found to degrade rapidly in the physiological environment and also to produce adverse effects. The first metal alloy developed specifically for human use was "vanadium steel" in the early 1900's.The earliest successful implants were bone plates, introduced in the early 1900s to stabilize bone fractures and accelerate their healing. As early as the first bone plate implants, surgeons identified material and problems that resulted in premature loss of implant function, as evidenced by mechanical failure, corrosion, and poor biocompatibility. Design, material selection, and biocompatibility remain the three critical issues in today's biomedical implants and devices.

During the 20th century (in mid 1920s) type 316 stainless steel was developed and was found to be stronger than previous alloys and having higher resistance to corrosion in body fluids. In the 1930s, cobalt–chromium (CoCr) alloys were developed for the aerospace industry and were found to have superior characteristics to steel for many prosthetic applications. Around the middle of the 20th century, pure titanium implants, which have excellent biocompatibility, were used and over the next few decades, Ti alloys with superior mechanical characteristics to the pure metal were developed for orthopaedic surgery. In recent years, a new shape-memory alloy made of nickel–titanium and the high-strength multiphase nickel-cobalt base alloy called MP35N have been attracting considerable interest for the prosthetic implants (reference). Nowadays, CoCr and Ti alloys are the most widely used alloys for orthopaedic surgery, with 316 and 316L (low carbon) steel and nitinol, a nickel-titanium alloy, being used in specific situations and for specific applications.

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