Elbow x-ray

Four Questions

Anterior and posterior fat pad signs (in a case of an undisplaced fracture of the radius head which is not visible directly).

A normal anterior fat pad in a non-fractured arm.

1. Are the fat pads normal?
   • A visible ant. fat pad is normal but if displaced anteriorly (Sail sign) it is abnormal
   • A visible post. fat pad is always abnormal
   • What if have fat pad displacement but no fracture or displacement is identified?
     • Adults: Treat as radial head fracture
     • Peds: Be certain that neither an undisplaced supracondylar fracture nor a displaced internal epicondyle fracture is overlooked!
2. Is the radiocapitellar line normal?
   • A line drawn along the longitudinal axis of the radial head and neck should pass through the capitellum
     • If line does not pass through capitellum then dislocation of radial head is probable
   • Whenver there is a fracture of the ulnar shaft must evaluate the radiocapitellar line for possible radial head dislocation (Monteggia fracture dislocation)
   • This rule is always valid on a true lateral film
     • In pediatric cases the AP view may be misleading
3. Is the anterior humeral line normal?
   • A line drawn along the ant cortex of the humerus will have at leats 1/3 of the capitellum anterior to it
     • If less than 1/3 then strong probability of supracondylar fracture with distal fragment displaced posteriorly
4. Are the ossification centers normal (pediatric patients only)?
   • CRITOE (Capitellum, Radial head, Internal epicondyle, Trochlea, Olecranon, Lateral Epicondyle)
     • Dislocated elbow may result in avulsion of internal epicondyle
       • Because the trochlea ossifies after the internal epicondyle if you see the trochlea you must find the epicondyle!

See Also

• Elbow Diagnoses
• Elbow X-ray (Peds)

References

• Accident and Emergency Radiology

Video

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Elbow Ossification by Age (CRITOE)

Ossification Center	Age of Appearance (add 1yr for boys)
Capitellum	1yr
Radial head	3yr
Internal epicondyle	5yr
Trochlea	7yr
Olecranon	9yr
External epicondyle	11yr

Normal pediatric elbow alignment

Anterior "Sail sign"

Reading Film

• Anterior humeral line should intersect with middle third of capitellum
  • If not, consider supracondylar fracture or lateral condyle fracture
• Line drawn along axis of radial head and neck should pass through middle of capitellum
  • If not, consider fracture of lateral condyle, radial neck, Monteggia, or elbow dislocation
• Fat pads
  • Anterior may be normal or if large may be abnormal ("sail sign")
  • Posterior is always abnormal

See Also

• Elbow Diagnoses
• Elbow Fractures (Peds)