Fig. 1

Medial view and inferior view of the syndesmosis. The line connecting the two mid-points of the distal tibial shaft at 5 cm (points c, d) and 10 cm (points a, b) above the joint surface was defined as the Z axis (from inferior to superior). The points of e and g represent the most medial and lateral points of the anterior tibial edge while points f and h represent the most medial and lateral points of posterior tibial edge. The X axis (from medial to lateral) was determined by connecting the midpoints of lines ef and gh. The Y axis (from posterior to anterior) was a cross product of the X and Z axes. The origin (point o) was the midpoint of the line which connecting the midpoints of lines ef and gh. The positive or negative value of the motion surrounding a specific axis was based on the right-hand rule. α presents for dorsiflexion(+), β presents for inversion(+), and γ presents for internal rotation(+)