Ulnar variance--the effect of wrist positioning and roentgen filming technique.

Ulnar variance--the roentgenographic distance between contiguous articular surfaces of the distal radiocarpal and ulnocarpal joints--changes with wrist and forearm position. Supination increases the measurement of negative ulnar variance. Pronation decreases the measurement of negative ulnar variance. Wrist deviation and alterations of the x-ray beam in the longitudinal plane also influence the measurement. A standardized wrist roentgenogram has been developed to allow accurate and reproducible measurements of ulnar variance. Internal landmarks for recognizing the standard views are introduced. The use of standard wrist roentgenographic techniques for all wrist films is recommended.