Review Question - QID 596

The radiograph shows a trimalleolar ankle fracture, which can be associated with syndesmosis injuries. The syndesmosis acts to maintain the relationship of the fibula in the incisura fibularis of the distal tibia as well as the congruity of the ankle joint. Failure to detect these injuries can lead to lateral talar shift and negative outcomes. So, if there was an isolated fibula fracture, the stress examination would test the deep fibers of the deltoid ligament complex. However, in this case, with fixation of the fibula, widening of the ankle joint would require an injury to the syndesmosis, as this structure would prevent it after restoration of the lateral column of the ankle (fibula).

Beumer et al describe that stress radiographs may be performed by external rotation stress on the hindfoot or by providing a lateral "pull" on the distal fibula after fixation (Cotton test).

Park et al showed that "ankle stress radiographs taken in dorsiflexion-external rotation were most predictive of deep deltoid ligament disruption after distal fibular fracture. Under this stress condition, a medial clear space of > or =5 mm was the most reliable predictor of deep deltoid ligament status."