Titanium nitride-based coatings on implantable medical devices

Abstract

Physical and chemical surface properties play an important role in the performance and clinical success of implantable devices. Once a prosthetic device is implanted, its surface becomes a site of various biochemical reactions and bacterial adhesion, as well micromotion and gross sliding. All these events can contribute to a less than optimal host response and eventually lead to the prosthesis failure. Creation of a surface coating is an attractive approach to alter the interaction of the implant with its surroundings since it allows modification of surface characteristics without changing the bulk material properties. Titanium nitride hard coatings have a long history of clinical use, especially on bearing surfaces of joint replacements. Moreover, there is an accumulating body of evidence suggesting that titanium nitride-based thin layers applied to non-articulating surfaces of various orthopaedic and blood-contacting implants result in improved clinical outcomes. Beyond the biological and functional requirements, a durable coating must strongly adhere to the device, i.e. be mechanically and chemically compatible with the substrate. The coating method (deposition vs. diffusion) has an important role to play in the adhesion of titanium nitride films. This paper is an overview of the current state-of-the-art of titanium nitride-based coatings on medical implants, methods of their deposition, in vitro properties, in vivo behavior and clinical performance.