Fig. 1.

A: The robotic system was used to load the hindfoot with use of a pressure-measurement sensor that was inserted into the ankle joint. B: The three-dimensional digitizer was used to define the coordinate system of the hindfoot. A line defined by Points 1 and 2 (medial and lateral malleoli) identifies the flexion axis, and a line defined by the midpoint of this axis and Point 3 (located at the center of the proximal part of the tibia) identifies the long axis of the tibia.