A 60 yo female presents with ankle pain after a fall from a ladder.  On exam patient has a grossly deformed left ankle and an inverted foot.  An xray is shown.  What's the diagnosis?  Scroll down for answer.

Answer:  Comminuted fracture of the talus with medial dislocation of the subtalar joint.  (Hawkins Type IV fracture of talus)

Subtalar dislocations

• Rare, account for 1-2% of foot/ankle dislocations
• There is disruption of the articulation of both the talocalcaneal and talonavicular joints
• may appear as an ankle dislocation but tibiotalar and ankle mortise are intact
• usually accompanied by fractures
• approximately 25% are open at initial presentation
• Medial subtalar dislocations (85%)
• foot inverted, calcaneous displaced medially
• AP xray will show medially displaced calcaneous as above and lateral will show talar head superior to navicular bone

• Lateral subtalar dislocations (15%)
• Foot is everted, calcaneous is displaced lateral to the talus
• lateral xray will show talar head inferior to navicular
• Prompt reduction is warranted with knee in flexion to relax the gastrocnemius
• 30% require open reduction
• High risk of infection for open fracture dislocation

Sources

Tintinalli's Emergency Medicine Manual, 8e Eds. Ch 175 Rita K. Cydulka, et al. New York, NY: McGraw-Hill

Giannoulis, Papadopoulus, Mavrodontitus, Subtalar dislocation without associated fractures: Case report and review of literature. World Journal of Orthopedics, 2015 April 18; 6(3): 374-379

Cervera, T. Subtalar Dislocation Case Report and Literature Review. Global Journal of Medical Research: Orthopedics and Musculoskeletal System

Eisenstein, Hillier, Ahmad, Medial subtalar dislocation with navicular and posterior talar process fracture: the first report in the literature, BMJ Case Report 2013: 2013: bcr2012007763