The potential biohazards of nanosized wear particles at boneprosthesis interface

Much attention has been paid to the nanoparticles (NPs) that are produced for applications in various areas, such as semiconductor or metallic NPs used in the fabrication of components, polymer additives in packaging, tires or NPs for catalysts or in sunscreen formulations, and oxide NPs applied in our daily life. These NPs are produced in the environment and may penetrate into the human body through outer-in routes, such as respiratory inhalation, gastrointestinal (GL) tract, or dermal and blood circulation.[1,2] However, there are some other ways in which NPs are generated in vivo and make the exposure of NPs different from the external environment and cause distinctive bioeffects. Less well realized by those interested in nanotoxicology is that there is also the possibility of an internal exposure to particles from surgical implants in the orthopedic field (Fig. 1). In this paper, we will mainly address wear debris continuously generated from motion taking place at the articulating surfaces. Artificial hip joints have been used for endoprostheses since the middle of the last century. Approximately 1 000 000 joints are replaced annually worldwide, with a rising tendency. Metals, ultra high molecular weight polyethylene (UHMWPE), and ceramics are the three main materials used in the design of implant components for hip and knee replacement. In early 1976, Harris already reported the extensive localized bone resorption resulting in implant loosening without resulting in infection in hip arthroplasty. After that, aseptic loosening became the most common cause of revision of major arthroplasties. Among various causes resulting in aseptic loosening, wear particles is the major one