ELBOW-Lieve It When I See It
Author: Nina Kouprina MD, Editor: Jeffery Greco MD
Elbow fractures are common in children and adults. These types of fractures encompass fractures of the distal humerus, proximal ulna, and proximal radius. In children, supracondylar fractures comprise the majority of elbow fractures, whereas in adults, radial head and neck fractures account for the majority. Plain radiography is the diagnostic standard, with the presence of abnormal fat pads being indicative of an occult elbow fracture. However, this sign may be subtle and thus may be misinterpreted as negative.
Question: can POCUS be used to diagnose an elbow fracture?
Background
Anatomy of the elbow joint:
In a normal elbow radiograph, the anterior fat pad may be visible as a thin stripe, while the posterior fat pad should not be visible. The presence of an abnormal fat pad (anterior and/or posterior) on radiography indicates the presence of an elbow joint effusion, resulting in elevation of the anterior or posterior fat pads (see figure below). In turn, these findings suggest the presence of a fracture of one or more bones at the elbow in the setting of trauma. Elevation of the anterior fat pad is also known as the “sail sign.”
The case
A 6 year-old female presents s/p a mechanical fall with left elbow pain
Her vital signs are normal. Physical examination reveals tenderness and swelling of the left elbow when compared to the normal elbow. The left elbow is held adducted in flexion. Range of motion is limited secondary to pain. There are no neurovascular deficits in the injured extremity.
Unfortunately, XR is not available for at least an hour…
You decide to use the ultrasound machine to evaluate for signs of injury, and this is what you see:
You compare it to a normal image of the left elbow:
Compared to the normal side, the fat pad on the right side appears more displaced.
Meanwhile, the XRs are completed and read as a supracondylar fracture with a large joint effusion (see figure below and notice the abnormal fat pads).
Case conclusion: patient is splinted and discharged home with orthopedic follow up.
POCUS of the posterior elbow
In terms of approach, you need a linear transducer. The elbow should be flexed at 90 degrees. It may be more comfortable for the patient to place the elbow on a table. Remember to compare with the normal side as well. The figure below demonstrates the technique for the long axis view:
Next, rotate the probe 90 degrees for the short axis view and scan at the level of the olecranon fossa:
Here is another example of an elevated posterior fat pad (FP) of the right elbow (long axis view) in the presence of an occult elbow fracture.
Compare to the normal left elbow:
Here is an example of a large joint effusion with a displaced posterior fat pad (long axis view):
Here is an example of an elevated posterior fat pad in the short axis view:
Again, compare to the normal elbow:
Summary
• Elbow fractures are common, but may be missed on radiography
• The posterior fat pad sign suggests the presence of an occult elbow fracture
• Ultrasound can also demonstrate an elevated posterior fat pad or a joint effusion indicative of an occult elbow fracture
• Compared to radiography, ultrasound is fast and convenient
• Ultrasound may be a useful screening tool for elbow fractures and help expedite further management
References
• Rapid screening for the posterior fat pad sign in suspected pediatric elbow fractures using point-of-care ultrasound: a “FAST exam” for the traumatized elbow. James W. Tsung, Michael Blaivas. Critical Ultrasound Journal, May 2010, Volume 1, Issue 3, pp 111–116.
• Point-of-Care Ultrasound: Sonographic Posterior Fat Pad Sign: A Case Report and Brief Literature Review. Yoshito Okumura MD, Nestor Maldonado MD, Kyle Lennon MD, Bryan McCarty MD, Philipp Underwood MD and Mathew Nelson DO, FACEP. Journal of Emergency Medicine, 2017-07-01, Volume 53, Issue 1, Pages 98-101.
• Ultrasound evaluation of elbow fractures in children. Kolja Eckert, Ole Ackermann, Bernd Schweiger, Elke Radeloff, Peter Liedgens. Journal of Medical Ultrasonics, October 2013, Volume 40, Issue 4, pp 443–451.
• Bredenkamp JH, Jokhy BP, Uehara DT. Chapter 267. Injuries to the Elbow and Forearm. In: Tintinalli JE, Stapczynski J, Ma O, Cline DM, Cydulka RK, Meckler GD, T. eds. Tintinalli's Emergency Medicine: A Comprehensive Study Guide, 7e New York, NY: McGraw-Hill; 2011. http://accessmedicine.mhmedical.com/Content.aspx?bookid=348§ionid=40381758. Accessed October 20, 2019.
• Radunović, G., Vlad, V., Micu, M.C., Nestorova, R., Petranova, T., Porta, F., & Iagnocco, A. (2012). Ultrasound assessment of the elbow. Medical ultrasonography, 14 2, 141-6 .