Humeral Neck Fracture
The AXILLARY VIEW is required to properly characterize humeral neck fractures. The Neer classification system is used by orthopedics to classify these injuries, further details can be found here. An example of the importance of obtaining the axillary view is shown in the next two images, both from the same patient. If the patient is going to be put in a sling and discharged, this view can often be deferred until the follow up visit. If orthopedics is consulted to see the patient in the ED, they will insist upon this view (which is painful in acute fractures and requires analgesia).
AP View: Only shows a surgical neck fracture line and it appears as a one-part fracture.
Axillary View: showing significant impaction of the humeral head and displacement of the greater tuberosity, meaning the fracture is actually three parts and thus a different classification.
The Axillary View will require a significant amount of analgesia as it is quite painful for the patient with a humeral neck fracture.