Initial dual mobility designs consisted of a cementless, monoblock acetabular component with a highly-polished metal inner bearing surface. Modular dual mobility prostheses have been introduced in which a modular cobalt-alloy liner is inserted into a hemispherical titanium acetabular component. Advantages of this construct include familiarity of use of a standard titanium acetabular component and the ability to use supplemental screw fixation. However, the potential for fretting corrosion between the cobalt-alloy liner and the titanium acetabular component remains a concern.