MyPACS.net: Radiology Teaching Files > Case 472566

never visited FAT PAD SIGN IN ELBOW INJURIES.
Contributed by: Tracy Campbell, Medical Student, Creighton University Medical Center, Nebraska, USA.
Patient: 2 year 1 month old female
History: Patient presents with a tender elbow after falling on an outstreched hand.
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Fig. 1: Lateral view of injuried elbow in a 2y1m old. Notice the subtle fat-pad sign. Both anterior and posterior fat pads are elevated and displaced.

Fig. 2: The fat-pad sign is traced in this radiograph. Both the anterior and posterior fat pads are visible and displaced upward and outward. With a positive fat-pad sign a fracture should always be suspected even if it is subtle.

Fig. 3: Another example of an elbow injury in a 4 y/o male. Note the displacement of the anterior and posterior fat pads leading to a positive fat-pad sign. Always evaluate the position of the capitellum realtive the anterior humeral line and longitudinal axis of the proximal radius.

Fig. 4: Note that the anterior humeral line does not bisect the capitellar ossification. Also note the visible posterior fat pad (displaced) and the obliterated anterior fat pad. Suspect an elbow fracture.
Findings: No fracture is visible on X-ray. The lateral view demonstrates elevation of the anterior and posterior fat pads. Remember, even if a fracture cannot be visualized on a radiograph, the fat-pad sign suggests the presence of an occult fracture. Follow up radiographs with an oblique view should be suggested.
Diagnosis: Positive fat-pad sign with displacement of the anterior and posterior fat pads. Also there is displacement of the anterior humeral line consistent with a supracondylar fracture.
Discussion:

With subtle elbow fracture the value of soft tissue swelling and the anterior humeral line cannot be stressed enough. The presence or absence of the fat-pad sign should always be assessed. With a history of trauma a fracture should always be considered with a positive fat-pad sign. Elevation and displacement of the fat pads denotes fluid in the joint, obliteration denotes periarticular edema and swelling. Both anterior and posterior fat pads can be displaced. Unlike the anterior fat pad, the posterior fat pad is not normally visible, thus if it is visible it is displaced. The fat pads can be hazy or obliterated due to edema around the elbow.

Note that the anterior humeral line does not intersect the capitellum through its middle third. If the anterior cortex of the distal humerous does not intersect the middle third of the capitellum, an abnormality is possible.

Treatment: Non displaced supracondylar fractures are immoblized in a long arm cast and surgery is not need.

References:

Swischuk, Leonard E., M.D. Emergency Imaging of the Acutely Ill or Injured Child, 3rd ed. Baltimore: Williams & Wilkins, 1994.
Greenspan, Adam, M.D. Orthopedic Radiology A Practical Approach, 3rd ed. Philadelphia: Lippincott Williams & Wilkins, 2000.
Davis, Richard T., M.D. Pediatric Fracture Conference Presentation, University of Nebraska Medical Center, Department of Orthopedics, 2004

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Additional Details:

Case Number: 472566Last Updated: 06-01-2004
Anatomy: Skeletal System   Pathology: Trauma
Modality: Conventional RadiographExam Date: Access Level: Readable by all users
Keywords: elbow fat pad sign, fracture, upper extremity

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