Ankle Fracture on X-ray: Imaging Findings

Plain radiographs (AP, lateral, mortise views) are the first-line modality for ankle fractures. CT is indicated for comminuted fractures, posterior malleolus assessment, pilon fractures, and pre-operative planning of articular reduction. MRI adds value when X-ray and CT are negative but clinical suspicion remains high — particularly for non-displaced stress fractures, syndesmotic ligament integrity (AITFL, PITFL), and associated osteochondral talar dome injury. STIR sequences are the most sensitive for occult fracture marrow edema.

The Lauge-Hansen system predicts injury sequence based on the deforming force. A supination-adduction pattern injures the lateral ligaments (ATFL, CFL) before the medial malleolus, visible on MRI as lateral ligament disruption with a transverse fibular fracture. Supination-external rotation — the most common pattern — progresses from AITFL disruption through distal fibular spiral fracture to posterior malleolus and then deltoid injury. AI can help explain these classification terms, but it cannot confirm ankle stability. A clinician must review the full imaging study and examination findings.

Medial clear space widening greater than 4 mm on mortise radiographs is the classic surgical threshold, but MRI directly visualises the deep deltoid ligament. Complete deep deltoid disruption on coronal T2-FS — shown as a fluid-filled gap medially — combined with fibular fracture at or above the level of the tibial plafond (Weber B/C) indicates rotational instability requiring operative stabilisation. Intact deep deltoid fibres on MRI may support non-operative management even with equivocal stress-view radiographs.