What is the correct positioning of the forearm for an anteroposterior projection?

For an anteroposterior projection, the forearm should be extended with the hand supinated. This positioning allows for the best visualization of the bones in the forearm, as it places them in a natural alignment that minimizes overlap and distortion.

In this position, the radius and ulna are parallel to each other, preventing any superimposition of the two bones. This orientation helps radiologists to accurately assess any potential fractures or pathologies within the forearm by providing a clear image. Additionally, supination brings the palm of the hand facing upwards, which is standard for many anteroposterior imaging techniques as it exposes the anatomical structures of the forearm effectively.

In contrast, flexing the forearm or positioning the hand in pronation would lead to improper alignment of the bones and could obscure important details in the resulting image.