Fig. 4.

Radiographic measurements. Posterior-anterior projection (a); lateral projection (b). Line A represents the longitudinal axes of the radius (in both planes), determined by connecting two points (more than 2 cm apart) in the centre of the radial shaft. Line B is drawn from the most distal ulnar palmar corner of the radial articular surface and is perpendicular to line A. Line C connects the most distal ulnar palmar corner of the radial articular surface to the most distal part of the radial styloid tip. Line D abuts the most distal point of the articular surface of the ulna; it is parallel to line B thus perpendicular to the longitudinal axis of the radius. Line E is drawn at a convenient level perpendicular to the central long axis of the radius. Line F connects the most distal dorsal and palmar margins of the radial articular surface. The ulnar variance is defined as the length of the ulna relative to the radius, i.e., the distance (mm) between lines D and B. The radial inclination is the inclination of the distal radial articular surface in the coronal plane, i.e., the angle between lines B and C. Tilt describes the angulation of the distal radial articular surface in the sagittal plane, i.e., the angle between lines E and F