When there is a multifragmentary fracture at the level of the syndesmotic ligaments, this is classified as an AO/OTA 44B2.3 fracture.
This is usually associated with a medial injury, either a rupture of the medial collateral ligament, or transverse or oblique fracture of the medial malleolus.
One of the fibular fragments may represent the detachment of the tip of the main proximal fibular fragment. This usually bears some intact portion of the anterior syndesmotic ligament. It may become entrapped between the other fibular fragments.
The most common injury pattern occurs with axial loading of a maximally supinated foot. Progressive talar external rotation results in further opening of the fibular fracture, with posterior displacement of the lateral malleolus, corresponding to Lauge-Hansen supination external rotation stage III. Finally the talus exits the ankle mortise posteriorly and disrupts the medial collateral structures, corresponding to Lauge-Hansen supination external rotation stage IV. In about 5% of malleolar fractures, the injury cause is a forced abduction of the hind part of the pronated foot (corresponds to Pronation-abduction fractures, stage I-III in the Lauge-Hansen classification).
Complete radiological evaluation (AP, lateral and AP with internal rotation) is crucial for correct classification and decision making.