elbow lateral xray normal

Radiology teaching during medical school is variable, ranging from informal teaching to required clerkships.​1​ Many of us likely received an approach to a chest x-ray, but approaches to other studies may or may not have not been taught. We can do better! Enter EMRad, a series aimed at providing approaches and improving interpretation of commonly ordered radiology studies in the emergency department. When applicable, it will provide pertinent measurements specific to management, and offer a framework for when to get an additional view, if appropriate. To begin: the elbow. 

Learning Objectives

  1. Interpret elbow x-rays using a standard approach
  2. Identify clinical scenarios in which an additional view might improve pathology diagnosis

Why the elbow matters and the radiology rule of 2’s

The Elbow

  • Approximately 2-3% of all ED visits involve the elbow.​2​
  • Missed elbow injuries can be highly morbid.

Before we begin: Make sure to employ the rule of 2’s​3​

  • 2 views: One view is never enough.
  • 2 abnormalities: If you see one abnormality, look for another.
  • 2 joints: Image above and below the injury (especially for forearm and leg).
  • 2 sides: If unsure regarding a potential pathologic finding, compare it to another side.
  • 2 occasions: Always compare with old x-rays if available.
  • 2 visits: Bring the patient back for repeat films.

An approach to the traumatic adult elbow x-ray

  1. Adequacy/Alignment
  2. Effusions or fat pads
  3. Bones
  4. Consider an additional view

1. Adequacy/Alignment

  • Lateral View
    • Check for a “Figure of 8” to ensure that this is a true lateral view.
elbow xray figure of 8
Figure 1: Lateral x-ray of the elbow demonstrating “figure of 8” in blue. Case courtesy of Dr. Craig Hacking, Radiopaedia.org
  • Anterior humeral line
    • A line drawn along the anterior aspect of the humerus should intersect the middle ⅓ of the capitellum.
    • If it does not, consider distal humerus fracture.
  • Radiocapitellar line
    • A line drawn along the middle of the radius should intersect the capitellum.
    • If not, consider radial head dislocation or subluxation.
elbow xray lines
Figure 2: Lateral x-ray of the elbow demonstrating the anterior humeral line (orange) and radiocapitellar line (red). Case Courtesy of Dr. Craig Hacking, Radiopaedia.org

2. Check for effusions or fat pads

Lateral View

  • An anterior fat pad can be normal but if excessive or “sail sign” think radial head fracture in adults
  • An posterior fat pad is always pathologic. In adults, this indicates intra-articular trauma.
elbow xray fat pads
Figure 3: Lateral x-ray of the elbow demonstrating a significant anterior fat pad (red arrows) and a posterior fat pad (blue arrows). Case courtesy of Dr. Ian Bickle, Radiopaedia.org

How do you know when too much is too much? The normal anterior fat pad is typically parallel to the humerus, usually angulated ≤15 degrees from the humeral shaft. When there is a significant effusion, it appears more angulated or like a sail, hence a “Sail Sign.”​4​

3.   Bones

Figure 4: Lateral x-ray of the elbow demonstrating humerus (green), radius (violet), and ulna (pink). Case courtesy of Dr. Craig Hacking, Radiopaedia.org
  • Trace the bone cortex carefully on both AP and lateral views.
  • Pay close attention to all aspects of the humerus, radius, olecranon.
Figure 5: AP x-ray of the elbow demonstrating humerus (green), radius (violet), and ulna (pink). Case courtesy of Dr. Craig Hacking, Radiopaedia.org

4. Consider an additional view

External Oblique View

  • When: Sometimes included as the 3rd view in a series
  • Why: This is better at seeing the radial head. Consider obtaining this view if there is a high suspicion for radial head fracture.
elbow xray coyles view
Figure 6: “White” arrow shows subtle defect in radial head. Case courtesy of wikiradiography.net

Coyles View

  • When: High index of suspicion for radial head fracture
Figure 7: Coyles view of elbow demonstrating subtle radial head fracture between the two green arrows. Case courtesy of Dr. Mahmoud Yacout Alabd, Radiopaedia.org

Learn More

References:

  1. 1.
    Schiller P, Phillips A, Straus C. Radiology Education in Medical School and Residency: The Views and Needs of Program Directors. Acad Radiol. 2018;25(10):1333-1343. https://www.ncbi.nlm.nih.gov/pubmed/29748045.
  2. 2.
    Goldflam K. Evaluation and treatment of the elbow and forearm injuries in the emergency department. Emerg Med Clin North Am. 2015;33(2):409-421. https://www.ncbi.nlm.nih.gov/pubmed/25892729.
  3. 3.
    Chan O. Introduction: ABCs and Rules of 2. In: ABC of Emergency Radiology. John wiley & Sons, Ltd; 2013:1-10.
  4. 4.
    Blumberg S, Kunkov S, Crain E, Goldman H. The predictive value of a normal radiographic anterior fat pad sign following elbow trauma in children. Pediatr Emerg Care. 2011;27(7):596-600. https://www.ncbi.nlm.nih.gov/pubmed/21712751.
Stephen Villa, MD

Stephen Villa, MD

Medical Education Fellow
Department of Emergency Medicine
University of California, Los Angeles
Stephen Villa, MD

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