Fig. 3.

Lateral view of left clubfoot talus (grade IV). a Center of the lateral trochlea arc is determined. b Tangent at the apex of the navicular articular surface. c Perpendicular line at the tangential point. It gives the direction of the talar neck, and intersects the radius AA′ of the talar trochlea arc. d At the point of intersection of line C, a horizontal line d is traced determining the inclination angle γ