Wrist Kinematics

Abstract

Analysis of radiographs of 52 wrists showed that, from ulnar to radial deviation, the amount of scaphoid shortening and ulnar translation of the scaphoid varies in a normal distribution. There is a significant correlation between the two measurements, such that the more the scaphoid shortens the less it translates and vice versa. Females subjects were more likely to have greater scaphoid shortening and less translation. It is felt that carpal kinematics thus cover a spectrum from the “row” theory to the “column” theory which is normally distributed and that women are more likely to have a column type wrist. This variation may affect the result of treatment of scapho-lunate dissociation by techniques such as scapho-lunate fusion. A “CR index” is proposed so that the tendency of a wrist towards row or column theory can be quantified. This may be used to predict the success of some surgical procedures in the treatment of scapho-lunate dissociation.