What is the required tube tilt for an external rotation of the shoulder?

In external rotation of the shoulder, the positioning of the X-ray tube does not require any tilt. When performing this view, the patient's arm is rotated externally, allowing the greater tubercle of the humerus to be clearly visualized in profile. The anatomical alignment and orientation achieved through the external rotation provide adequate visualization of the shoulder structures without the need for additional angulation of the X-ray tube.

This approach ensures that the shoulder joint is captured in a true anatomical position, which is crucial for accurate diagnosis and assessment. A direct central beam perpendicular to the film or detector is sufficient, allowing for optimal imaging without the complexity that would be introduced by tilting the tube. Hence, the correct answer reflects the necessity for a neutral tube positioning for this particular X-ray projection.