By: Terry R. Yochum, DC, DACBR, Fellow, ACCR, Michael S. Barry, DC, DACBR, and Chad J. Maola, DC
This young adult male fell on an outstretched hand, locking his elbow while jogging. He immediately experienced pain on the lateral side of the elbow. Can you find the abnormality?
Observe the radiolucent fracture of the radial head with impaction of the metaphysis of the radial neck.
Fractures of the Proximal Radius
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.1 In children and adolescents, the incidence is significantly lower, with a frequency of approximately 15%.2 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 capitellum. 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.3 In the presence of a positive fat-pad sign if a fracture is not identified specific radial head views may demonstrate a fracture of the radial head.4
Radial Head Fracture. The fracture line may be subtle and easily overlooked, so the observer must search for the various signs that indicate an occult fracture.10
Fracture line. A radiolucent line is seen usually oriented 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 fracture’s fragment may produce a ‘double cortical’ sign, which is seen as a linear opacity paralleling the normal articular cortex of the radial head.5
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.6
Fat-pad sign. A useful sign of an intraarticular fracture of the elbow is the clear depiction of displaced humeral capsular fat-pads.7 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 oriented radiolucency. When acute intracapsular swelling is present from any origin (hemorrhagic, inflammatory, or traumatic), the anterior fat pad is elevated to be oriented horizontally, while the posterior fat pad will now be visible (‘fat-pad’ sign).8 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 intraarticular effusion. In children and adolescents, 90% of posterior fat-pad signs will have an associated fracture.7 In adults the sign is less frequently seen, and its absence does not exclude the presence of a fracture.8,10
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.9,10
- Conn J, Wade PA. Injuries of the elbow. A ten year review. J Trauma 1961; 1:248.
- Rogers LF. Radiology of Skeletal Trauma, Vols. 1 and 2 (2nd ed.). New York: Churchill Livingstone, 1992.
- Schultz RJ. The Language of Fractures. Baltimore: Williams & Wilkins, 1976.
- Hall-Craggs MA, Shorvon PJ, Chapman M. Assessment of the radial head — capitellum view and the dorsal fat-pad sign in acute elbow trauma. AJF 1985; 145:607.
- Nelson S. Some important diagnostic and technical fundamentals in the radiology of trauma, with particular emphasis on skeletal trauma. Radiol Clin North Am 1966; 4:241.
- Rogers SL, MacEwan DW. Changes due to trauma in the fat plane overlying the supinator muscle: a radiologic sign. Radiology 1969; 128:643.
- Norell HG. Roentgenologic visualization of the extracapsular fat. Its importance in the diagnosis of traumatic injuries to the elbow. Acta Radiol 1954; 42:205.
- Hunter RD. Swollen elbow following trauma. JAMA 1974; 230:1573.
- Essex-Lopresti P. Fractures of the radial head with distal radioulnar dislocation. J Bone Joint Surg (Br) 1951; 33:244.
- Yochum TR, Rowe LJ. Essentials of Skeletal Radiology (2nd ed.). Baltimore: Williams & Wilkins, 1996.
About the Authors
Dr. Terry R. Yochum is a second generation Chiropractor and a cum laude graduate of the National College of Chiropractic, where he subsequently completed his radiology specialty. He is a Diplomate of the American Chiropractic Board of Radiology and served as its vice-president and president for seven years (1983-1990).
Dr. Michael S. Barry is a 1988 cum laude graduate of Palmer College of Chiropractic. He completed a three-year radiology residency at Logan College of Chiropractic following two years of clinical practice in Las Vegas, Nevada. He received his diplomate in radiology from the American Chiropractic Board of Radiology in 1992.
Drs. Yochum and Barry interpret and consult with clients regarding all aspects of diagnostic imaging, including plain film and advanced imaging procedures.