Image Interpretation Course
by Heidi Nunn DCR(R) PgCert
The Shoulder
Fracture prevalence | Projections | Normal paediatric anatomy
Proximal humerus | Clavicle | Scapula | Glenoid
Anterior dislocation | Posterior dislocation | AC joint subluxation | Pseudo-subluxation
Rotator cuff arthropathy | Bony metastases | Simple bone cyst
(click on images to enlarge)
Fracture prevalence
- A fall onto the shoulder tends to result in specific injuries depending on the general age of the patient:
Under 10 years
Fractured clavicle 15-40 yearsAcromio-clavicular joint subluxation Gleno-humeral joint dislocation Under 20 years and over 60 yearsFractured proximal humerus
Projections
- AP – then view image.
The second image may be: - Supero-inferior axial or infero-superior axial if the AP is normal, and the patient can easily abduct their arm.
- Modified axial, or lateral scapula “Y” view. The patient does not need to abduct their arm for these views and these projections can be easily obtained with the patient on a trolley.
Normal paediatric anatomy
- In the unfused skeleton, the epiphyseal growth plate for the proximal humerus appears as two lucent lines. Commonly mistaken for fractures.
- Also, secondary ossification centres are often seen at the acromion and the coracoid processes:
12 years14 years15 years17 years
- On the axial view, the ossification centre for the coracoid process may develop from the base or the tip. Both may simulate fractures:
Proximal humeral fractures
- Humeral neck (anatomical and surgical), and greater tuberosity should be assessed carefully for evidence of:
Break to the cortex
Disruption to the trabecular pattern
Sclerosis, suggesting impaction
- In the paediatric skeleton, the proximal humeral metaphysis should be examined carefully for cortical disruption:
- Assess the whole film (inc. ribs and lung), particularly injury due to high velocity, eg, RTA:
Clavicle fractures
- Are usually easy to spot. If the fracture is minimally displaced and overlies the scapula/ribs, an angled up projection is helpful.
- Fractures of the middle third of the clavicle are most common (especially in <20 year olds). Fractures of the lateral third are more likely to be seen in an older age group. Fractures of the medial third are uncommon.
Scapula fractures
- Will occur due to high velocity, eg, RTA.
- Can be subtle due to overlying ribs/clavicle. If the mechanism of injury fits, then the scapula must be scrutinised, particularly the blade and spine of the scapula, and also the corocoid and acromion processes:
Glenoid fractures
- Fractures to the anterior lip of the glenoid are usually very subtle and are therefore easily missed. They may occur due to direct trauma or following anterior dislocation.
Anterior dislocation
- Often occur due to sporting injuries.
- Humeral head lies under the coracoid on the AP. On the axial it’s displaced towards the coracoid. On the modified axial and lateral scapula “Y” view, humeral head is displaced towards the ribs/coracoid.
- Important to identify associated fractures. Common fractures involve:
- the postero-lateral aspect of the humeral head (Hill-Sachs deformity):
- the anterior lip of the glenoid (Bankhart lesion):
- the greater tuberosity:
- the postero-lateral aspect of the humeral head (Hill-Sachs deformity):
Posterior dislocation
- Tend to occur due to muscle spasm during epileptic fits, or electric shock.
- The humerus is usually internally rotated, therefore the humeral head has a “light bulb” appearance on the AP. This is not always the case, however. There is widening of the joint (>6mm) as the humeral head is displaced laterally; this is called the rim sign. On the axial, the humeral head will be displaced towards the acromion/away from the ribs:
- Associated with avulsion fractures of the lesser tuberosity. Also, a medial and anterior humeral head compression fracture may be evident (trough line).
AC joint subluxation
- Width of the normal joint is less than 7mm in adults. Widening indicates moderate sprain with rupture of the acromioclavicular ligament.
- The inferior surfaces of the lateral clavicle and the acromion should be level. Subluxation is identified when the clavicle is elevated due to rupture of the coracoclavicular ligaments:
Pseudo-subluxation
- Blood within the joint causes inferior subluxation of the humeral head, however, this is not a true dislocation. Look for a possible underlying fracture:
Rotator cuff arthropathy
- Occurs in association with RA. Causes superior elevation of the humeral head with erosions developing on the inferior surface of the acromion. Causes impingement of the supraspinatus muscle.
Bony metastases
- Primary tumours often metastasise to the proximal humerus, and it is important to search for any moth-eaten, lytic lesions, or areas of sclerosis.
- Potential lesions may be an incidental finding on a non-fractured humerus, or the fracture may be pathological in origin:
Simple/Solitary/Unicameral bone cyst
- A benign lytic lesion that is often seen at the diametaphyseal region of the proximal humerus. Again, may be an incidental finding, however, will sometimes fracture.
- “Falling fragment sign” is sometimes seen, which refers to cortical fragments from the fracture, which fall through the fluid-filled lesion:
