Answer radER Vol 1.3

radER Winners:

Scott Ottolini           Julie Nguyen         Richard Gordon

Allison Loynd          Rob Klever            Marjan Siadat

Answer to Case 1.3

A 35-year-old man presents to your ED complaining of elbow pain after tripping on a patch of ice and landing on his outstretched hand.  You administer pain medication and obtain the following radiograph:

1. Name 2 abnormal findings on this radiograph?

2. What is the diagnosis?

3. What is the ED treatment and follow up for this patient?


1. An anterior and posterior fat pad sign

2. Occult radial head fracture

3. Sling, for comfort, pain medication, early range of motion exercises and orthopedic follow up

Physical Exam

The patient will fully flex their elbow but will not fully extended the elbow particularly the last 5-10º of extension.  This should also tip you off that there is a radial head fracture prior to taking x-rays.

A good lateral radiograph of the elbow is taken with the elbow held at 90° of flexion.  Normally you may see a lucency that represents fat present along the anterior surface of the distal humerus, and no lucency should be visualized along its posterior surface. A positive fat pad sign is when there is either an elevated anterior lucency, also known as a “sail” sign since it resembles a sail on a boat, or if a posterior fat pad is visible at all on a well taken lateral radiograph of the elbow.  Either a positive anterior or posterior fat pad is consistent with an occult fracture of the radial head.  Any elbow joint distention either hemorrhagic, inflammatory or traumatic gives rise to a positive fat pad sign.

Why do these occur?
Three small masses of fat rest in the radial, coronoid, and olecranon fossae and are enveloped by the fibers of the joint capsule separating the fat pads from the synovial lining.  This means that the fat pads are intracapsular and extrasynovial in location. The anterior fat pad consists of the radial and coronoid fat pads, which are normally pressed into the shallow radial and coronoid fossae by the brachialis muscle. On a lateral radiograph of the normal elbow the anterior fat pad is normally seen as a vertical faint line that is more radiolucent than adjacent muscle and is parallel to the anterior distal humerus. The posterior fat pad is normally pressed into the deep olecranon fossa by the triceps tendon and anconeus muscle and is invisible on a lateral radiograph of the normal elbow.
Thank you for everyone who submitted an answer. Please stay tuned for next week’s radER.

radER is a weekly contest, hosted by Dr. Kerin Jones’ “Fracture”,  consisting of a radiograph selected from various areas of emergency medicine that are central to the education of medical students and residents in training.

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