Mobile-bearing total ankle arthroplasty.

Total ankle arthroplasty has followed two major design concepts: Mobile-bearing and constrained. The US Food and Drug Administration has not approved mobile-bearing designs. Therefore most of the experience and design of these replacements has been in Canada and Europe. Hydroxyapatite coats often used in Europe also are not used in the United States. This article focuses primarily on the various design characteristics of the different mobile-bearing designs and reviews the outcome research to date.