Elbow Pain and Swelling After a Fall

Differential Diagnosis

• Fat pad sign
• Osteolytic lesion
• Radial head fracture
• Elbow dislocation
• Nightstick fracture

Diagnosis
The x-ray reveals a fat pad sign, or elevated posterior fat pad, with positive elbow joint effusion. The lateral view of the elbow shows a focal area of lucency in the posterior aspect of the elbow at the level of the olecranon fossa, closely apposed to the bone.

Learnings

• Normal fat in the olecranon fossa is not visible unless uplifted by joint effusion.
• Elbow fractures may not be evident on an x-ray, but secondary signs, such as a fat pad elevated by bleeding, may indicate that there is a fracture.
• An anterior fat pad is often normal, but if elevated it is abnormal.
• A posterior fat pad seen on a lateral x-ray of the elbow is always abnormal. If a posterior fat pad is identified without a visible fracture, then an occult fracture should be suspected and will be present up to 75% of the time.
• In adults, an occult fracture is usually found to be a radial head fracture, whereas in children it is typically a supracondylar fracture.

Pearls for Initial Management and Considerations for Transfer

• When performing an x-ray of the elbow, look for a dislocation, bony lesion, fracture, or abnormal fat pad.
• If a fracture is not seen, but an abnormal fat pad is seen, treat the patient “as if” a fracture were seen, with immobilization and orthopedic referral.
• Indications for emergent transfer may include intractable pain, uncertainty of diagnosis, possibility of compartment syndrome, consideration of septic arthritis or necrotizing soft tissue infection (NSTI), potential for dislocation, or a Salter-Harris fracture.