EMRad: Radiologic Approach to the Pediatric Traumatic Elbow X-ray

This is EMRad, a series aimed at providing “just in time” approaches to commonly ordered radiology studies in the emergency department [1]. When applicable, it will provide pertinent measurements specific to management, and offer a framework for when to get an additional view, if appropriate. We recently covered the adult elbow, here we will cover the approach to the pediatric elbow.

Learning Objectives

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

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

The Pediatric Elbow

• 10% of all pediatric fractures involve the elbow [2].
• Missed injuries can cause significant deformity, pain, or functional/neurologic complications [2].

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 (especially for forearm and leg).
• 2 sides: If unsure regarding a potential pathologic finding, compare 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 pediatric elbow x-ray

1. Adequacy / Alignment
2. Effusions or Fat Pads
3. Bones, Growth Plates, and Ossification Centers
4. Consider an additional view

1.   Adequacy / Alignment

• Check for a “Figure of 8” to ensure that this is a true lateral view.
• Check the anterior humeral line.
  • Pearl: Children (usually those under age 4) can have the anterior humeral line pass through the anterior third of the capitellum without associated pathology [2].
  • Pearl: In pediatric patients, abnormalities in the anterior humeral line can indicate a supracondylar fracture or a lateral condyle fracture
• Check the radiocapitellar line.
  • Pearl: In pediatric patients, abnormalities in the radiocapitellar line can indicate multiple possible pathologies: radial head dislocation (and the associated Monteggia fracture), radial neck fracture, lateral condyle fracture, or an elbow dislocation.

2.   Effusions or Fat Pads

• An anterior fat pad can be normal, but is considered pathologic if excessively prominent (usually around ≥20 degrees from the humerus, or “sail sign”).
• A clearly visualized posterior fat pad is always pathologic.
• If either the sail sign or posterior fat pad is present, consider a supracondylar fracture or intra-articular fracture (e.g. lateral condyle fracture )

Figure 1: Measurement of apical angle of the anterior fat pad ≥ 20 degrees, concerning for sail sign. There is also a visible posterior fat pad. Case courtesy of Dr. Ian Bickle, Radiopaedia.org. Annotations by Daniel Ichwan, MD.

3.   Bones, Growth Plates, and Ossification Centers

Figure 2: Lateral and AP x-rays of the elbow demonstrating humerus (green), radius (violet), and ulna (blue). Case courtesy of Dr. Jeremy Jones, Radiopaedia.org. Annotations by Daniel Ichwan, MD.

• Immature bones with open growth plates (physes) are susceptible to injuries (Salter-Harris fractures) with important growth implications.
  • The Salter-Harris classification is as follows below:
    • Salter-Harris Type 1 (“Slipped”) – epiphysis (part of bone between the growth plate and adjacent joint) separates from metaphysis (neck portion of a long bone).
      • Pearl: Can appear radiographically normal, but tender on physical exam.
      • Requires splinting and ortho follow-up.
    • Type 2 (“Above”) – involves metaphysis (“above the physis”).
      • Requires splinting and ortho follow-up.
    • Type 3 (“Lower”) – involves epiphysis (“below the physis”).
      • Consult orthopedics in the department.
    • Type 4 (“Through”) – involves both the metaphysis and epiphysis.
      • Consult orthopedics in the department.
    • Type 5 (“Erasure”) – crushing of physis. May appear normal or focal narrowing of physis.
      • Consult orthopedics in the department

Figure 3: Salter-Harris Classification. Case courtesy of Dr. Matt Skalski, Radiopaedia.org.

• Pediatric bones have a stronger periosteum than the underlying incompletely ossified bones.
  • Watch out for bowing, torus, greenstick, or avulsion injuries.
• Trace each bone’s cortex carefully on both AP and lateral views.
• Pay close attention to all aspects of the humerus, radius, and ulna.
• Locate each expected ossification center per the patient’s age.
  • If there is one missing or seemingly prematurely present, consider a fracture.

Figure 4: Ossification centers on (a) AP pediatric elbow x-ray (case courtesy of Dr. Leonardo Lustosa, Radiopaedia.org) and (b) lateral pediatric elbow x-ray. Note that not all ossification centers are visible in this view (case courtesy of Dr. Ian Bickle, Radiopaedia.org. Figure 6 (b) annotations by Daniel Ichwan, MD

Table 1: Order and timing of appearance of elbow ossification centers. Some people remember this order by using the mnemonic “CRITOE”: capitellum, radial head, internal (medial) epicondyle, trochlea, olecranon, and external (lateral) epicondyle.

4.  Consider an Additional View

Oblique View

• When: Sometimes included as the 3rd view in a series
• Why: This is better at seeing the radiocapitellar joint, medial epicondyle, radioulnar joint, and coronoid process. Consider obtaining this view if there is a high suspicion for a subtle lateral condyle fracture or radial head fracture.

Figure 6: Lateral oblique x-ray of the elbow. Case courtesy of Dr. Craig Hacking, Radiopaedia.org.

X-rays of Contralateral Elbow

• Given variation among patients, sometimes it might be necessary to image the contralateral extremity to clarify whether the questionable finding is pathologic or actually normal.

References

1. Schiller, P. et al. Radiology Education in Medical School and Residency. The views and needs of program directors. Academic Radiology, Vol 25, No 10, October 2018. PMID: 29748045
2. DeFroda SF, Hansen H, Gil JA, Hawari AH, Cruz AI Jr. Radiographic Evaluation of Common Pediatric Elbow Injuries. Orthop Rev (Pavia). 2017;9(1):7030. Published 2017 Feb 20. PMID: 28286625
3. Chan O. Introduction: ABCs and Rules of 2. In: ABC of Emergency Radiology. John Wiley & Sons, Ltd; 2013:1-10.
4. Blumberg SM, Kunkov S, Crain EF, Goldman HS. The predictive value of a normal radiographic anterior fat pad sign following elbow trauma in children. Pediatr Emerg Care. 2011 Jul;27(7):596-600. PMID: 21712751
5. Black KL, Duffy C, Hopkins-Mann C, Ogunnaiki-Joseph D, Moro-Sutherland D. Musculoskeletal Disorders in Children. In: Tintinalli JE, Stapczynski J, Ma O, Yealy DM, Meckler GD, Cline DM. eds. Tintinalli’s Emergency Medicine: A Comprehensive Study Guide, 8e. McGraw-Hill; Accessed December 22, 2020. https://accessmedicine.mhmedical.com/content.aspx?bookid=1658&sectionid=109408415

Author information

Stephen Villa, MD

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

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