Abstract
Total joint arthroplasty is a safe and effective procedure as an end-stage treatment for arthritis. In the case of hip replacement mean patient age has decreased from sixty-eight to sixty-five years over the past eight years, raising concerns over implant longevity and the complications that occur in association with revision surgery.
The dominant mode of failure of total joint replacements is aseptic loosening, which in many cases is caused by the reaction of bone to the presence of implant debris. In an attempt to increase implant longevity, bearing surfaces that minimize the volume of debris generated from the articular surface are being developed. Ultra- high molecular weight polyethylene, which has been the mainstay of arthroplasty, changing the material with which the polyethylene articulates has also been addressed in an effort to further improve wear characteristics.
Oxinium is the brand family name of a material used for replacement joints manufactured by the reconstructive orthopedic surgery division of medical devices company Smith & nephew. It consists of a Zirconium alley metal substrate that transitions into a ceramic Zirconium oxide outer surface. The ceramic surface is extremely abrasion resistant compared to traditional metal implants such as cobalt chromium. It also has a lower coefficient of friction against ultra-high molecular weight polyethylene(UHMWPE), The typical counter face material used in total joint replacements.
These two factors likely contribute to the significantly lower UHMWPE wear rates observed in simulator testing.
Reducing UHMWPE wear is thought to decrease the risk of implant failure due to osteolysis. All ceramic material can have a similar effect in reducing wear, but are brittle and difficult to manufacture. The metal substrate of oxinium implants makes component easier to manufacture and gives them greater toughness(a combination of strength and ductility). In essence, this technology combines the abrasion resistance and low friction of a ceramic with the workability and toughness of a metal.
