Mobility of the human ankle and the design of total ankle replacement.

Our prior research has shown that currently available total ankle implants fail to restore physiologic ankle mobility. Most of the modern mobile-bearing designs that feature a flat tibial component and a talar component with anatomic curvature in the sagittal plane function nonphysiologically with the natural ligament apparatus. To establish a more natural relationship between the implanted components and the retained ankle ligaments, we have developed a new design. According to our prior research, we suggest that physiologic ankle mobility is reproduced best with a design featuring a spherical convex tibial component, a talar component with radius of curvature in the sagittal plane longer than that of the natural talus, and a fully conforming meniscal component. Our preliminary observations in trial implantation and in a few patients suggest that while reproducing physiologic ankle mobility, the new design is capable of maintaining complete congruence at the two articulating surfaces of the meniscal bearing over the entire motion arc, with the prospect of minimizing wear of this component.