Ankle morphometry on 3D-CT images.

Understanding three-dimensional (3D) morphology of the ankle is essential for a better total ankle replacement. Current designs neither mimic the articular geometry at the bearing surface interfaces nor match the native bony bed with the implant's external dimensions. This is likely due to insufficient anthropometric data on sizing and geometry. We performed this study to determine the range of possible sizes of ankle joints based on high-resolution 3D-CT images. Clinical 3D-CT images from twenty-one normal ankles (11 males, 10 females) were subjected to morphometric evaluation. A local coordinate system for measurement was established based on talar anatomic landmarks. Measurements included the width of the superior talar dome surface (measured at the anterior, middle, and posterior portions) and the arc radius of the talar dome. The results yielded an average anterior width of 29.9 +/- 2.6 mm, a middle width of 27.9 +/- 3.0 mm, and a posterior width of 25.2 +/- 3.7 mm. The talar dome radius was 20.7 +/- 2.6 mm. The width linearly decreased from anterior to posterior (p < 0.001). A significant gender difference was found in both the width and the radius (p-values < 0.05), except at the middle width (p = 0.07). The data describe talar topography in a Caucasian U.S. adult cohort, suggesting the capability of the 3D-CT approach for ankle morphometric evaluation and sizing for the fabrication of total ankle replacements.