Age / Sex : 22 / F

Chief complaint : pain and joint limitation after sports injury (taekwondo)

What is your impression?

Two weeks later, you can see the final diagonosis with a brief discussion of this case (Please submit only one answer).

Courtesy : Dong-Ho Ha, Dong-A university Hospital

Discussion

Answer: Isolated radial head posterior dislocation

Findings:

Plain film 

Disruption of radiocapitellar line

: A line drawn down the neck of the radius should intersect the capitellum. It is important to ensure that you draw the line down the radial neck and not along the shaft because of the slight angulation at the neck of the radius. If the line does not intersect the capitellum, there is radial head dislocation.

Differential Diagnosis:

Radial head dislocation

Diagnosis: 

Isolated radial head posterior dislocation

Discussion:

Isolated dislocation of the radial head without concomitant ulnar fracture or humeroulnar subluxation in adults is a rare injury.

Most of the earlier reported cases were in children and were considered Monteggia variants.

The mechanism leading to an isolated radial dislocation has been variously described. Most authors describe an indirect mechanism.

The dislocation can be occurred anteriorly and posteriorly.

References:

Apollo Medicine,2014, Volume 11, Issue 2, 137-139

J Med Case Reports. 2007; 1: 38.

J Orthop Case Rep. 2015 5(1): 73–75.