Pronation and supination of the scaphoid.

The objective of this study was to identify and classify longitudinal rotations of the scaphoid on clinical radiographs of normal wrists. The concept of scaphoid recumbency was defined in terms of the orientation of the palmar tubercle. Pronation and supination of the scaphoid were identified in a set of 130 posteroanterior films of structurally normal wrists in neutral position. Normal variations in scaphoid recumbency and lunate posture were classified. It was found that the scaphoid is in neutral recumbency in 62%, pronation in 32%, and supination in 7% of structurally normal wrists. Neutral scaphoid recumbency and neutral lunate posture occur together in 45% of normal wrists. Rarely, scaphoid supination and lunate flexion occurred together, simulating a collapse pattern often seen in inflammatory arthritis. Scaphoid supination and lunate extension did not occur together. An anatomic basis for this incompatibility of scaphoid recumbency and lunate posture is suggested. We conclude that longitudinal rotation of the scaphoid (ie, pronation and supination) may be seen on clinical radiographs of structurally normal wrists. These rotations are exaggerated in certain types of carpal instability.