Working Diagnosis:
Massioneuve fracture and posterior malleolus fracture.

Treatment:
Due to the instability of the ankle with a Maisonneuve fracture, she underwent surgical fixation of the syndesmosis four days after clinic evaluation and 16 days from her injury. Case Photo #7 , Case Photo #8 . She remained non weight bearing for 6 weeks after surgery and then progressed in a boot over two months. She returned to skateboarding at 5 months post surgery.

Author's Comments:
Posterior malleolar fractures are commonly associated with instability of the ankle joint and are typically non-isolated injuries. Apparent isolated posterior malleolar fractures may be associated with Maisonneuve fractures. One mechanism of injury of a Maisonneuve fracture is external rotation of the foot, which results in a force transmitted through the interosseous membrane and exits at the proximal fibula. The widening of the medial joint space and the posterior malleolar fracture exhibited on radiographs are both consistent with injury involving external rotation of the ankle. Although the patient cannot recall specific details of her injury, it is probable she experienced this mechanism of injury causing the resulting injuries.

Editor's Comments:
Posterior malleolar fractures occur in over 40% of ankle fractures (Weber B or Weber C) and are rarely an isolated injury. Therefore, an "isolated" posterior malleolus fracture should trigger further clinical evaluation for other fracture, ligamentous, or syndesmotic instability. Typically the mechanism of injury results from rotational mechanism: supination and adduction, supination and external rotation, or pronation and external rotation. This case illustrates the need for full examination for concomitant injury, stress radiographs to assess stability of the fractures, and importance computerized tomography scan plays in fracture assessment.

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