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Ankle Case 3 Diagnosis

Malleolar Fractures

Diagnosis is by plain radiographs (AP, lateral, and mortise views):

Note whether fibular fractures are distal, proximal, or at the level of the tibia-fibula syndesmosis. The lateral view is best for assessing the posterior tibial articular surface.

On the mortise view (taken with the leg in 15 degrees internal rotation), measure the distance between the talus and medial malleolus (the "medial clear space"); >4mm suggests instability.
An additional view to assess stability is a mortise stress view. This is taken with the examiner holding the leg internally rotated with one hand while the foot is externally rotated with the other hand. Medial clear space > 5 mm on stress view suggests ankle instability, either from medial malleolar fracture or deltoid ligament rupture. This view can often be deferred until orthopedics follow-up.