Elbow Case 3 Diagnosis

Supracondylar humerus fracture

Diagnosis is made by plain films. Pediatric fractures often occur through the growth plate, so a fracture line may not be visible. Therefore, it is important to check for alignment and any soft tissue abnormalities. A true lateral elbow film is crucial to assess these things.

Pathologic fat pads on the lateral film indicate an elbow effusion, which, in the setting of trauma, is assumed to be from hemarthrosis from an intraarticular fracture.

• A visible posterior fat pad (red arrow) is always pathologic.
• An anterior fat pad (blue arrow) is considered pathologic if it is displaced superiorly and assumes the shape of a sail (the "sail sign").

Alignment is assessed by drawing a longitudinal line along the anterior border of the humerus on the lateral view. This line normally bisects the capitellum. If this line falls in the anterior third or entirely anterior to the capitellum, a posteriorly displaced supracondylar fracture is likely. This "anterior humeral line" is particularly important to check in pediatric films.