A 32-year-old male presents to the ED after an inversion ankle injury during a football match. AP mortise view X-ray is obtained. The structure marked **D** (mortise joint space) shows widening of the medial clear space to 6 mm, which is greater than the tibiotalar superior clear space of 3 mm. The ankle mortise appears asymmetric. No obvious fibular fracture is visible on the ankle series. Which of the following is the most appropriate next step in management?

Explanation

## Why option 1 is right Widening of the medial clear space (>4 mm) in the mortise joint space (**D**) on the mortise view X-ray indicates deltoid ligament injury or lateral talar shift, signifying an **unstable ankle injury**. This finding is a critical red flag for associated **syndesmotic injury** and potential **proximal fibular fracture (Maisonneuve fracture)**, which may not be visible on standard ankle series. According to Apley's Orthopedic Surgery, widening of the medial clear space alone warrants imaging of the proximal fibula to exclude a high fibular fracture with syndesmotic disruption—a classic teaching point in ankle trauma. This is an unstable injury requiring surgical planning, not conservative management. ## Why each distractor is wrong - **Option 2**: Conservative management (cast alone) is inappropriate for an unstable ankle injury. Widening of the medial clear space indicates deltoid ligament injury and potential syndesmotic disruption, which require operative fixation (ORIF) if confirmed. Casting without addressing the underlying instability risks chronic ankle instability and poor functional outcome. - **Option 3**: Immediate arthroscopy is not the next step. The priority is to **rule out a proximal fibular fracture and syndesmotic injury** through imaging. Arthroscopy may be considered intraoperatively during ORIF if there is concern for intra-articular pathology, but it is not the first diagnostic step for an unstable mortise widening. - **Option 4**: While MRI is useful for soft tissue assessment, it does not address the immediate need to exclude a **Maisonneuve fracture**. Plain radiography of the proximal fibula is the standard, efficient next step. MRI may be obtained later for ligamentous detail if needed, but it should not delay the diagnosis of a high fibular fracture. **High-Yield:** Medial clear space widening on mortise view = unstable injury; always check the proximal fibula for Maisonneuve fracture and assess syndesmosis. [cite: Apley 10e — Ankle Mortise, Fibular Fractures, Weber Classification, Maisonneuve Injury]