A 38-year-old female from Mumbai slipped on a wet floor and twisted her right ankle inward. She presents with moderate pain and swelling localized to the lateral ankle. On examination, the ankle is stable with no gross deformity. Plain radiographs show a fracture of the fibula 6 cm proximal to the ankle joint with an intact medial malleolus and no posterior malleolar involvement. There is widening of the medial ankle space on the mortise view. What is the most appropriate diagnosis?

Explanation

## Diagnosis: Unimalleolar Fracture with Syndesmotic Injury (Maisonneuve-type) ### Definition A **Maisonneuve fracture** is a high fibular fracture (typically in the proximal third, but any fracture ≥6 cm proximal to the ankle joint) associated with disruption of the **syndesmotic ligament complex** and often the **deltoid ligament**, resulting in ankle instability despite an intact medial malleolus. **Key Point:** The defining features are: (1) fibular fracture well proximal to the ankle joint, (2) intact medial malleolus, and (3) widening of the medial ankle space on mortise view indicating deltoid ligament rupture and syndesmotic disruption. ### Classic Presentation | Feature | Maisonneuve / Syndesmotic | Pott Fracture | Bimalleolar | |---------|--------------------------|---------------|-------------| | **Fibular fracture level** | ≥6 cm proximal to joint / proximal fibula | At or just above lateral malleolus (distal fibula) | At lateral malleolus | | **Medial malleolus** | Intact (deltoid ruptured) | Intact (deltoid ruptured) | Fractured | | **Syndesmosis** | Disrupted | Usually intact | Variable | | **Mortise view** | Widened medial space | Widened medial space | Variable | **High-Yield:** A fibular fracture **6 cm proximal** to the ankle joint with medial space widening is the radiographic hallmark of a Maisonneuve-type injury — a subset of unimalleolar fractures with syndesmotic disruption. This is distinct from a classic Pott fracture, where the fibular fracture is at the level of the distal fibula/lateral malleolus. ### Mechanism of Injury External rotation (and/or pronation) forces cause: 1. Deltoid ligament rupture → medial ankle space widening 2. Syndesmotic ligament disruption (anterior and posterior tibiofibular ligaments, interosseous membrane) 3. Force propagates proximally along the interosseous membrane → high fibular fracture **Clinical Pearl:** The proximal fibular fracture may be missed if the entire fibula is not imaged. Any patient with medial ankle space widening and no medial malleolus fracture should have full-length fibula radiographs to exclude a Maisonneuve fracture (per Rockwood & Green's Fractures in Adults). ### Why Not Pott Fracture? Pott fracture (as classically described by Percivall Pott, 1768) involves a **distal fibular fracture at or near the level of the ankle joint** combined with deltoid ligament rupture. The fracture in this stem is **6 cm proximal** to the ankle joint — this location is inconsistent with a classic Pott fracture and instead indicates a Maisonneuve-type syndesmotic injury. ### Management **High-Yield:** Maisonneuve fractures with syndesmotic disruption are **unstable** injuries requiring **operative fixation** — typically syndesmotic screw placement (or tightrope fixation) to restore the mortise, with or without fixation of the fibular fracture depending on its level and displacement (per Campbell's Operative Orthopaedics). **Warning:** Do NOT treat this injury conservatively. The syndesmotic and deltoid ligament disruption renders the ankle mortise unstable, predisposing to post-traumatic arthritis if not anatomically reduced and stabilized.