By: Terry R. Yochum, DC, DACBR, Fellow, ACCR, and Chad J. Maola, DC
This young adult male patient falls on a hyperextended elbow and has immediate pain on the lateral aspect of the elbow. X-rays were taken at the emergency room to rule out fracture. What do you see?
There is an impaction fracture of the radial head with a vertical radiolucent “chisel-like” fracture of the articular surface of the radial head. This represents an impaction fracture of the radial head.
Fractures of the radial neck and head are the most common fractures of the adult elbow, accounting for approximately 50% of all injuries to this region. In children and adolescents, the incidence is significantly less, with a frequency of approximately 15%. The majority of proximal radius fractures are due to a fall on an outstretched hand, transmitting a longitudinal axis of force to create impaction of the radial head into the capitelum. An incomplete fracture of the radial head which extends from the center of the articular surface for approximately 10 mm is called a “chisel” fracture.
Radial Head Fracture
A number of radiological signs must be searched for, since the fracture line may be subtle and easily overlooked:
Fracture Line. A radiolucent line is seen usually orientated vertically and penetrating the articular cortex toward the lateral side of the head.
Cortical Disruption. At the fracture site, the cortex will be broken.
Cortical Deformity. At the fracture site, a sharp step-off or angulation is common, due to fragment displacement. Depression of the fractured fragment may produce a “double cortical” sign which is seen as a linear opacity paralleling the normal articular cortex.
Altered Supinator Fat Line. On a normal lateral film, a linear radiolucent line representing the outer fascial plane of the supinator muscle, 1 cm above the anterior radial surface, will be observed. In fractures of the radial head or neck the fat line may be obliterated, blurred, or ventrally displaced by more than 1-2 cm.
Fat Pad Sign. A useful sign of an intra-articular fracture of the elbow is the clear depiction of displaced humeral capsular fat pads. In the normal elbow a layer of fat (“fat pad”) lies between the synovial and fibrous layers of both the anterior and posterior joint capsule. In the lateral projection of the normal elbow the anterior fat pad is seen as an obliquely orientated radiolucency. When acute intracapsular swelling is present from any origin (hemorrhagic, inflammatory or traumatic), the anterior fat pad is elevated to be orientated horizontally, while the posterior fat pad will now be visible (“fat pad” sign). In joint distensions the elevated fat pads, especially anteriorly, may be obliterated due to hemorrhage or edema; therefore, the posterior fat pad, when visible, is the most reliable sign of intra-articular effusion. In children and adolescents, 90% of posterior fat pad signs will have an associated fracture. In adults the sign is less frequently seen, and its absence does not exclude the presence of a fracture.
Radial Neck Fracture
The most common fracture is an impaction at the junction of the head and neck. The only sign may be a sharpened angle on the anterior surface, best depicted on the lateral projection. Complete fractures will be readily seen as a transverse lucent line with varying degrees of displacement. A comminuted fracture of the radial head in combination with dislocation of the distal radioulnar joint is called an Essex-Lopresti fracture.
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2. Resnick D, Niwayama G. Diagnosis of Bone and Joint Disorders, 2nd ed. Philadelphia: W. B. Saunders Co., Philadelphia, 1988.