Rotation may lead to misinterpretation of heart contours, tracheal position and lung appearances
If the patient is very rotated and you do not recognise this, certain appearances may become misleading.
Principles of rotation
The spinous processes of the thoracic vertebrae are in the midline at the back of the chest. They should form a vertical line that lies equidistant from the medial ends of the clavicles, which are at the front of the chest. Rotation of the patient will lead to off-setting of the spinous processes so they lie nearer one clavicle than the other.
The spinous processes should lie half way between the medial ends of the clavicles
Does rotation matter?
If the patient is rotated then interpretation may become difficult. Firstly, it may be difficult to know if the trachea is deviated to one side by a disease process. It also becomes difficult to comment accurately on the heart size. Changes in lung density due to asymmetry of overlying soft-tissue may be incorrectly interpreted as lung disease.
Rotation and heart size
Heart size can be assessed accurately with a well-aligned posterior-anterior (PA) chest X-ray. If the patient is rotated to their left, then the heart may appear enlarged. If the patient is rotated to their right, then heart size may be underestimated.