A 24 yo male presents with ankle pain after attempting a flip and twisting his ankle.  Plain films are shown.  What's the diagnosis?  Scroll down for answer.

Answer:  Disruption of the ankle mortise and syndesmosis with posterior malleolus fracture

• most common mechanism of injury is external rotation
• commonaly missed injury so must pay close attention to mortise and talofibular overlap
• normal medial clear space <4mm  -- space between medial malleolus and talus)
• normal tibiofibular clear space is <6mm -- space between the lateral border of the posterior tibia (incisural fibularis) and the medial border of the fibula (measured 1cm proximal to plafond)
• positive squeeze test = pain at distal syndesmosis with squeeze at mid tibia/fibula
• stress radiographs may be helpful, CT or MRI if clinical suspicion is high in the setting of normal plain films
• commonly associated with proximal fibular fracture (Maisonneuve, which this patient had)
• instability suggested by stress radiographs is an indication for surgery
• good functional outcomes are seen with anatomic reduction

Reference:

Hunt, K. J. (2013). Syndesmosis injuries. Current Reviews in Musculoskeletal Medicine, 6(4), 304-312. doi:10.1007/s12178-013-9184-9