Bones are the densest structures visible on a normal chest X-ray. Despite this it is easy to overlook important abnormalities of the bones which may be very subtle.
The bones visible on a chest X-ray include the clavicles, the ribs, the scapulae, the spine, and the proximal humeri (upper arms). The sternum is also included on a frontal view but it overlies other midline structures and so is obscured.
The bones are used as useful markers of chest radiograph quality. They are used to assess patient rotation, adequacy of inspiration and X-ray penetration.
The spinous processes of the vertebrae (posterior structures) and the medial ends of the clavicles (anterior structures) are landmarks to assess rotation
The ribs should be checked on every chest X-ray
The right 5th rib is highlighted (roll-over image)
The clavicle and ribs act as landmarks when assessing the adequacy of inspiration taken by the patient
The anterior end of approximately 5-7 ribs should be visible above the point at which the mid-clavicular line intersects the diaphragm
Less than 5 ribs indicates incomplete inspiration
More than 7 ribs suggests lung hyper-expansion
On this normal X-ray the anterior end of the 7th rib (asterisk) intersects the diaphragm at the mid-clavicular line
The subcostal grooves are visible on the underside of the ribs (red highlights)
These grooves contain the subcostal nerves and vessels that accompany each rib
Note: To avoid damaging the subcostal nerves or vessels the superior edge of a rib is used as the landmark during procedures such as chest drain insertion
The spine can be seen through the heart indicating adequate X-raypenetration
Acute rib fractures are often invisible, therefore chest X-rays are not helpful if there is clinical suspicion of a rib injury unless a complication such as pneumothorax is suspected.
Occasionally you will see an important abnormality of the bones on a chest X-ray such as bone metastases. Bone abnormalities may be very subtle, so always look carefully at all the bones when viewing a chest X-ray.
