A 4 year old boy presents after falling onto his elbow. Here’s the AP view:
It’s seldom this obvious, but the child has a supracondylar humeral fracture. Diagnosis usually requires looking at the lateral film for the presence of a fat pad.
Fat pads represent joint effusions; in the elbow the two types are the ‘anterior’ and ‘posterior’ ones. Anterior fat pads may be normal, but presence of a posterior fat pad is always abnormal. Presence of a posterior one implies an occult fracture. In children, it represents a condylar humeral fracture. In adults it suggests a radial head fracture.
Here’s this patient’s lateral film:
Resolution in that is not the best so here is a clearer example:
Pretend the AP view was normal. If you see this on the lateral film, you must treat as if there is an occult fracture (splint, orthopedics follow-up).
Another key feature of lateral films: to make sure it’s an adequate film, look for the exclamation point. If it’s not there, you may not be able to reliably judge the presence of a posterior fat pad.
