When there is a simple, displaced, oblique fracture at the level of the syndesmotic ligaments, associated with a rupture of the medial collateral ligament, this is classified as an AO/OTA 44B2.1 fracture.
The anterior syndesmotic ligament is ruptured, or it may be avulsed, either at its fibular (Le Fort / Wagstaff), or tibial (Tillaux-Chaput) insertion.
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).