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)	Age at Fusion
Capitellum	1yr	12-14 yrs
Radial head	3yr	14-16 yrs
Internal epicondyle	5yr	16-18 yrs
Trochlea	7yr	12-14 yrs
Olecranon	9yr	15-17 yrs
External epicondyle	11yr	12-14 yrs

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)