The effect of rotational malalignment on X-rays of the wrist.

This study evaluates the effect of rotational malposition of the wrist on measured radiographic parameters of the distal radius and carpus. Ten wrists from five healthy volunteers were imaged in varying degrees of rotation. The wrists were placed in a custom, calibrated jig and images were taken in 5 degrees increments to a maximum pronation and supination of 20 degrees . The results demonstrate the following: a steady decrease in the scapholunate and radioscaphoid angles with extremes of supination; an increase in palmar tilt with supination and a decrease in palmar tilt with pronation. The palmar tilt varied from -4 degrees to 15 degrees and the scapholunate angle ranged from 48 degrees to 29 degrees at the extremes of rotation. These results demonstrate how malrotation in X-ray positioning can have a significant effect on the apparent alignment of the distal radius and carpal bones. Measurements taken from poor X-rays typically fall outside the normal range and could adversely effect treatment decisions.