Assessment of reduction

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 Assessment of reduction in ankle fractures
 Mortise displacement
 Shortening of the fibula
 Assessment of reduction in type C ankle fractures
Assessment of reduction in ankle fractures

Three radiographic views of the ankle are required:

  • Anteroposterior view
  • Lateral view
  • AP view obtained in 15° or 20° angle of internal rotation to bring the transmalleolar axis parallel to the plate (mortise view)

 


Mortise displacement

The line of the articular surface of the talus should be parallel to the ankle mortise line. The joint space between the talus and tibial plafond should equal the space between the medial malleolus and medial talus. The distance between the articular side of the medial malleolus and the respective articular surface of the talus should be less than 4 mm.


Shortening of the fibula

Fibular shortening can be recognized radiographically as a step in the alignment of the subchondral plates of the tibial plafond and the lateral malleolus.

The articular surface of the lateral malleolus bears a small “spur” at its proximal extent and the curve of this is continuos with the image of the tibial plafond on the internal rotation view of the ankle – the so-called “Shenton’s line” of the ankle. Any step in this line indicates fibular shortening.

The tip of the fibula touches the circumference of a circle that corresponds to the lateral arch of the calcaneum.


Assessment of reduction in type C ankle fractures

The distance between the medial cortex of the fibula and the posterior edge of the incisura fibularis should be less than 5mm.

The distance between the medial cortex of the fibula and the anterior edge of the incisura fibularis should be more than 10mm.

 


Shortening of the fibula in 44-C fractures is best detected by comparison of x-rays of the injured ankle with those of the uninjured side.


Rotational displacement of the fibula is difficult to evaluate on radiographs. A CT scan of both ankles is recommended.