Oxinium Oxidised Zirconium Knee Replacements from Smith and Nephew

The Orthopaedic division of Smith and Nephew Inc have developed a new knee implant. The implant is patented and known as Oxinium.

Oxinium implants are made of an oxidized zirconium metal. It is claimed to be of greater benefit to younger, more active recipients of knee replacements. This is because the traditional knee implants are made of cobalt-chrome alloys that articulate against polyethylene surfaces. The friction involved with normal human movement results in wear of the metal and plastic components, and the production of wear debris. The eventual wear of the components results in the need to replace implants later in life, which becomes more difficult each time the surgery is required.

The Oxinium implants are claimed to be 160 times smoother and 4900 times more abrasion resistant than cobalt-chrome models.

Ceramics go some way to reducing wear, but are known to be brittle. The zirconium alloy used in the Oxinium implants is heated to oxidize the surface, thus producing zirconium oxide on the surface, providing a product which offers the reliability of metals, with a wear resistant ceramic surface.

Testing in knee simulators has shown that polyethylene wear is reduced by as much as 85% using the Oxinium material.

Approximately 8% of the population suffer from nickel allergies, which used to mean that they had few alternatives. The zirconium alloy used in the Oxinium implants does not contain any detectable amounts of nickel, so is safe for these people to use, providing yet another advantage over cobalt-chrome materials.

To date, Oxinium knee implants have been in clinical use for over 5 years and have been used in over 17,000 patients worldwide. Smith and Nephew intend to used the Oxinium technology in hip replacements where the benefit to this specific patient group could be even greater.

Posted July 2003