Ligamentous ankle and midfoot injuries with ankle haemoarthrosis

Case contributed by Henry Knipe
Diagnosis almost certain

Presentation

Fall from height onto inverted ankle. Numbness in the side of the foot and fourth and fifth toes. Pain on weight-bearing. X-ray no fracture.

Patient Data

Age: 40 years
Gender: Male

Large subcutaneous hematoma overlying the anterolateral ankle. Ankle and posterior subtalar joint hemarthrosis with synovial thickening.

No osteochondral injury of the talar dome or distal tibial plafond. Mild bone marrow edema in the plantar lateral cuboid. No other focus of bone marrow edema. No fracture or focal osseous lesion is seen.

Syndesmotic ligaments are intact. Anterior talofibular ligament and calcaneofibular ligament are completely torn. Heterogeneity of deep deltoid ligament with a minor focus of medial talar bone marrow edema at the site of partial tear anteriorly. Superomedial spring ligament is partially torn with redundancy of the tibiospring ligament. Edema of both the medioplantar and inferoplantar spring ligament. Dorsal talonavicular ligament high signal. High signal of the lateral limb bifurcate ligament, medial limb appears intact. 

Mild edema within the sinus tarsi, interosseous talocalcaneal and lateral cervical ligaments appear intact. Likely partial tear of the lateral limb of the extensor retinaculum. Plantar fascia origin is normal. Achilles tendon insertion is intact.

Small tendon sheath effusion of tibialis anterior and extensor hallucis longus adjacent to the hematoma. Small tibialis posterior tendon sheath effusion, remaining flexor tendons are intact. Incidental peroneus quartus. Small tendon sheath effusion of peroneus longus and brevis with a short interstitial split tear of the inframalleolar peroneus brevis tendon.   

Case Discussion

Severe ligamentous injury of the ankle involving the medial and lateral collateral ligaments and midtarsal joint primarily involving the spring ligament. Ankle and posterior subtalar joint hemarthrosis is uncommon to see. 

The numbness in the foot presumably relates to compression of the lateral dorsal cutaneous nerve at the level of the distal fibula, although the nerve is not directly visualized given the degree of soft tissue edema and hematoma.

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