The global coordinate system of the ankle specimen. The fixation of the ankle specimen in the standard pose for imaging. The global coordinate system of the ankle specimen was defined with the origin at the geometric center of the talus. The anteroposterior (X) axis was defined as the line joining the calcaneal insertion of the Achilles tendon and the head of the second metatarsal. The superoinferior (Y) axis was defined as the tibial longitudinal axis which was perpendicular to the base-plate. The mediolateral (Z) axis was then defined as the line perpendicular to both the X- and Y-axes.