Findings:
Posterior gleno-humeral dislocation.
No evidence of a fracture.
Note (1):
There is loss of congruity at the gleno-humeral joint. This is best shown on the apical oblique view, ie the image on the right. The glenoid cavity and the the head of the humerus are not in alignment.
Note (2):
This abnormality - when present - will be evident on the standard two views of a painful or injured shoulder. Nevertheless, it is often not recognised by the first reader of the radiographs. There are two main reasons why the dislocation is frequently not recognised: (a) failure to consider that a posterior dislocation is a clinical possibility; (b) failure to understand the normal and abnormal anatomy on the two radiographs provided by the radiographer.
Note (3):
The two commonest causes of a posterior dislocation are an epileptic fit or an electric shock. In this case the patient is likely to have fitted whilst sleeping.
Note (4):
Different Emergency Departments will vary in their choice of the 2nd view. Obviously, an AP frontal view will always be provided.
The 2nd view provided here is an apical oblique view of the shoulder.
This particular radiographic projection is a 5 star view. It will show a posterior dislocation brilliantly; also, it is very good at revealing fractures (when present) of the head of the humerus or of the glenoid labrum.
Unfamiliar with the apical oblique view??
See : Accident & Emergency Radiology : A Survival Guide (3rd edition) : Pages 76 & 79