The anterior to posterior fibular gap illustrates the displacement of the proximal and distal fibular fragments in trans-syndesmotic lateral malleolar fractures on the lateral view of the ankle and might indicate a medial injury.
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Usage
The anterior to posterior fibular gap can be used in the setting of trans-syndesmotic fibular fractures (Weber B) to predict a medial injury.
Measurement
The anterior to posterior fibular gap is assessed on the lateral view of the ankle as the perpendicular distance between the anterior and posterior fibular fracture fragments 1,2.
Interpretation
An anterior to posterior fibular gap of ≥1 mm has been associated with widening of the medial clear space of ≥5mm on gravity stress radiographs of the ankle in one study 1,2. It is hypothesized that this might indicate a medial injury 2.
However, fibular displacement on the mortise view has been demonstrated to be a poor predictor 3. Also, a lack of any displacement should not be falsely interpreted as a sign of stability 4.