Potential of coatings in total hip replacement.

In total hip replacements, the bulk properties of materials, such as proper elasticity and hardness, are important. However, the material interacts with the body mainly at the surfaces. Wear and corrosion are initiated at the surfaces also. Therefore, the control of surface properties using different kinds of treatments or coatings may improve total hip replacements considerably. The most studied surface treatments include ion implantation and methods to control surface topography, such as grit or sand blasting or plasma treatments. Among the large variety of coatings, hydroxyapatite, titanium oxide and nitride, zirconium oxide, pyrolytic carbon, and diamondlike carbon coatings have shown the most promising results. These coatings mainly are used to enhance bone growth; to minimize friction, wear, and corrosion; and to improve biocompatibility of total joint prostheses. The potential of novel coatings to solve some present problems in joint prostheses is discussed based on the structure and properties of different kind of coatings. It can be concluded that currently, coating methods exist to improve the tribologic performance and longevity of the total hip replacements. However, coatings must fulfill two essential requirements: no delamination in biochemical and biomechanical environments and sufficient protection of substrate from corrosion.