Review Question - QID 489

The clinical presentation is consistent with a supination external rotation (SER) injury. An external rotation stress radiograph is the most appropriate method to assess the competency of the deltoid ligament.

Plain static radiographs alone can not be relied on to detect deltoid injury, which is one variable used to assess ankle stability. Various preoperative methods have been suggested, including the presence of medial tenderness, allowing the patient to weight bear with follow up radiographs, manual ER stress radiographs, and gravity ER stress radiographs. Evidence shows both a manual or gravity external rotation stress radiograph can indicate deltoid competency, although this isn't absolute.

Park et al. performed a cadaveric study of SER ankle injuries and found that a medial clear space of > or =5 mm on radiographs taken in dorsiflexion with an external rotational stress was most predictive of deep deltoid ligament transection after distal fibular fracture. All other stress conditions and increases in medial clear space of 2 or 3 mm were less predictive.

DeAngelis et al. performed a study to identify whether medial tenderness is a predictor of deep deltoid ligament incompetence in supination-external rotation ankle fractures. The identified 55 Weber B type fractures, and sought to correlate medial tenderness with positive stress radiographs. They found no statistical significance between the presence of medial tenderness and deep deltoid ligament incompetence.

Figure A shows a a spiral fibula fracture at the level of the tibial plafond, consistent with a supination external rotation (SER) injury. Illustration A shows the Lauge Hansen classification of supination-external rotation ankle injuries (SER 1-4). Illustration B shows an external rotation stress with medial clear space widening, indicating incompetent deltoid ligament. Illustration C shows a ankle gravity stress test where the patient lies in the lateral position and the ankle is allowed to hang down freely over a support. Finally, Illustration D shows an intra-operative example of the Cotton test, which involves direct lateral stress on the fibula with use of a clamp.

Incorrect Answers:
Answer 1: The anterior drawer assesses the anterior talofibular ligament and is a physical exam test that can be done pre/intra/postoperatively.
Answer 4: The lateral stress (Cotton) test is used intraoperatively to assess for syndesmotic injury (Illustration D). This test involves manual/clamp distraction of the fibula away from the tibia under fluoroscopy after stabilization of the lateral and medial malleoli.