Fig. 4

The tibiotalar contact ratio is assessed using 3 variables: the talar radius (r); the talar height (h); and the tibiotalar sector (α). By drawing a circle digitally fitted to the talar joint surface, the radius is determined by drawing a line to the middle of the circle, measured in millimeters (r). The height is determined drawing a line through the middle of the circle from the surface of the talus to the inferior border, measured in millimeters (h). From the center of the circle two lines are drawn to the anterior and posterior margins of the distal tibia, representing the tibiotalar sector (α)