Final answer:
To confirm a true lateral position of the hand and wrist in a lateral projection of the elbow, check that the radius and ulna are parallel and the humeral epicondyles are superimposed with no overlap.
Step-by-step explanation:
When viewing a lateral projection of the elbow, it is important to determine if the hand and wrist were in a true lateral position. This is crucial because an inaccurate position can affect the diagnostic quality of the radiograph. When a hand is in a true lateral position, the palm of the hand faces sideways, and in the case of the forearm, the radius and ulna should appear as parallel structures with no overlap. To ensure this, the patient's thumb should be pointed upwards and the hand should be in the mid-pronation/supination position, so that both the radius and the ulna are superimposed when viewed laterally. Additionally, the epicondyles of the humerus should be on the same plane, perpendicular to the film. Thus, signs of a true lateral position for the wrist and hand on an elbow radiograph include the visualization of the radius and ulna in parallel without overlap, and the elbow's lateral humeral epicondyle and medial epicondyle superimposed.