Fig. 2

Radiographic evaluation indices proposed by Fogel et al.: a Relative ulnar shortening. b Radial articular angle. c Ulnarward carpal slip. a Relative ulnar shortening (RUS) is measured with the perpendicular line drawn from the distal end of the ulna to the linear axis of the forearm. b The radial articular angle (RAA) is the angle between two constructed lines: one along the articular surface of the radius and the other perpendicular to a line that bisects the head of the radius and passes through the radial edge of the distal radial epiphysis. The normal RAA is 15°-30°. c Ulnarward carpal slip (CS) or displacement of the lunate off the radius is measured as the percentage of contact of the lunate with the radius. An axial line drawn from the center of the olecranon through the ulnar edge of the distal radius normally bisects the lunate. Carpal slip is considered abnormal when the lunate is displaced ulnarward by > 50%