Findings: A lateral view of the elbow demonstrates a positive "sail" sign indicative of displacement of the anterior fat pad. A posterior fat pad is not visualized.

An AP view of the elbow demonstrates a nondisplaced fracture of the radial head.

Diagnosis: Linear and nondisplaced fracture of the radial head.

Discussion: Fractures of the radial head are one of the more common elbow injuries in adults. They account for approximately half of all adult elbow injuries. The mechanism of injury is usually the result of a fall on an outstretched hand. The force of the injury is then transmitted along the radius to the radial head which presses against the capitellum and fractures.

The classification for radial head fractures is 1) linear and nondisplaced, 2) marginal 3) depressed and 4) comminuted. In addition, the Mason's classification is also used to describe fractures of the radial head. Type I is less than 2 mm displacement. Type II consists of displacement or depression of at least 2 mm and Type III consists of a comminution of the radial head.

Comminuted fractures of the radial head are usually well seen. Subtle radial head fractures may be visualized only on a single view, as in this case. However, bnormal anterior or posterior fat pad is a significant radiographic sign for an intra-articular fracture.

The Essex-Lopresti fracture is usually seen in severely comminuted fractures of the radial head with associated proximal migration of the distal radioulnar joint. Therefore, the examination of the wrist is recommended in cases of severely comminuted fractures of the radial head.

Treatment of nondisplaced fractures consists of casting. Long term sequelae include decreased range of motion secondary to intra-articular scar formation.

Reference:
Harris JH Jr., Harris WH, Novelline RA. Radiology of Emergency Medicine,
3rd Edition. Williams and Wilkins, Baltimore; 1993:352-360.

Rogers LF. Radiology of Skeletal Trauma, Vol II, 2nd Edition. Churchill
Livingstone, New York; 1992:788-795.

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