Fig. 1

a Posterioanterior measurement guidelines as described in Kreder et al. [6]. b Lateral measurement guidelines as described in Kreder et al. [6]. c Step and gap measurement as described in Kreder et al. [6]. a RA, radial angle; RL, radial length; UV, ulnar variance; RS, radial shift. 1) This line represents the long axis of the radius. The center of the radius shaft is determined at 3 cm and 5 cm below the mid-region of the proximal lunate articular surface. 2) A line perpendicular to the center long axis of the radius is drawn at the level of the most distal aspect of the radial articular surface. 3) A line perpendicular to the central long axis of the radius is drawn at the level of the ulnar margin of the distal radial articular surface. 4) The radial and ulnar margins of the distal radial articular surface are connected. 5) A line perpendicular to the central long axis of the radius is drawn at the level of the distal ulnar articular surface. 6) A line tangential to the most radial point on the radial metaphysis is drawn parallel to the central long axis of the radius. b PT palmar tilt angle (dorsal tilt=negative palmar tilt); DS, dorsal shift. 1) This line represents the long axis of the radius. The center of the radial shaft is determined at 3 cm and 5 cm below the mid-region of the proximal lunate articular surface. 2) A line perpendicular to the central long axis of the radius is drawn at a convenient level. 3) The dorsal and anterior margins of the distal radial articular surface are connected. 4) A line tangential to the most dorsal point on the radial metaphysis is drawn parallel to the central long axis of the radius. c 1) Step-off at the distal radius articular cortical margin is measured by drawing lines perpendicular with the central long axis of the radius from the most distal margin of each side of the cortical discontinuity. 2) Gap deformity is measured by dropping lines that are parallel from the central long axis of the radius from the most distal margin of each side of the cortical deformity. The gap distance is measured along a line perpendicular to the central long axis of the radius.