Structured oral examination question 1: Lateral ligament instability of the ankle

1. EXAMINER. Tell me what this diagram represents and name the structures labelled 2, 3 and 5. (Figure 4.1.)

2. CANDIDATE. This diagram is a representation of the lateral aspect of the ankle showingthe bony and ligamentous structures. Structure 2 is the anterior talofibular ligament, structure 3 is the calcaneofibular ligament and structure 5 is the posterior distal tibiofibular ligament.

3. EXAMINER. What structures are injured in a lateral ligament injury?

4. CANDIDATE. The mechanism is usually a rotational injury with sequential failure of the ligaments from front to back, hence the anterior talofibular ligament or ATFL is most commonly injured followed by the calcaneofibular ligament or CFL and the posterior talofibular ligament is the least frequently injured.

5. EXAMINER. How would you go about diagnosing a lateral ligament injury to the ankle?

6. CANDIDATE. In the acute setting I would expect the patient to give a history of an episode of a twisting incident resulting in significant pain and swelling. There may be a history of recurrent sprains and instability. Acutely the lateral side of the ankle would be swollen and tender anterior and inferior to the tip of the fibula but discomfort may make it difficult to elicit a definite sign ofinstability.

7. In a patient with a more chronic history the clinical sign of instability would be a positive anterior drawertest or talar tilt test.

8. EXAMINER. Tell me more about those two tests.

9. CANDIDATE. The patient is examined sitting with their legs over the edge of the couch or sitting in a chair to relax the gastrocnemius soleus complex. For the anterior drawer test the distal tibia is grasped in one hand and the other hand grasps the heel and the foot is drawn anteriorly in relation to the talus. Pain or excess anterior translation or a sulcus sign developing at the anterolateral corner of the ankle are signs of an ATFL injury. The other ankle must be examined for comparison. The talar tilt test involves inversion of the ankle whist palpating the anterolateral corner of the joint to feel for movement of the talus within the mortise. A lack of firm end point or tilt in excess of the normal side would represent instability and the CFL is considered to have been injured if this test is positive.

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