From the Guidelines
Posterior ankle dislocation images typically show the talus displaced posteriorly relative to the tibia, often with associated fractures, and standard imaging should include anteroposterior, lateral, and mortise views of the ankle. When evaluating these images, look for the talus positioned behind its normal articulation with the tibial plafond on lateral radiographs 1. The imaging characteristics of a posterior dislocation of the ankle can be assessed using various modalities, including radiography, CT, and MRI.
Key Imaging Characteristics
- The talus is displaced posteriorly relative to the tibia on lateral radiographs
- Associated fractures are common, particularly of the medial and lateral malleoli, posterior malleolus, and syndesmotic complex
- CT scans provide more detailed assessment of associated fractures and articular surface damage
- MRI may be indicated to evaluate soft tissue injuries, particularly ligamentous structures and the posterior tibial neurovascular bundle
Imaging Modalities
- Radiography: initial imaging study, includes anteroposterior, lateral, and mortise views of the ankle 1
- CT: provides more detailed assessment of associated fractures and articular surface damage, particularly useful for complex injuries such as posterior malleolar fracture and posterior pilon variant fractures 1
- MRI: may be indicated to evaluate soft tissue injuries, particularly ligamentous structures and the posterior tibial neurovascular bundle 1
Clinical Implications
- Prompt recognition of posterior ankle dislocations on imaging is crucial as these injuries represent orthopedic emergencies requiring immediate reduction to prevent skin necrosis, neurovascular compromise, and long-term complications such as post-traumatic arthritis
- The integrity of the medial and lateral malleoli, posterior malleolus, and syndesmotic complex should be carefully evaluated, as these structures are frequently injured in conjunction with posterior dislocations 1
From the Research
Imaging Characteristics of Posterior Dislocation of the Ankle
The imaging characteristics of a posterior dislocation of the ankle can be identified through various diagnostic tools, including:
- Radiographs: Initial assessment of the ankle dislocation and identification of any associated fractures 2
- Computed Tomography (CT) scan: Further evaluation of the ankle joint and surrounding structures to rule out any fractures or other injuries 2, 3
- Magnetic Resonance Imaging (MRI): Assessment of soft tissue injuries, including ligamentous and tendinous structures, as well as identification of any osteochondral lesions 2
Key Findings
Key findings on imaging studies for posterior dislocation of the ankle may include:
- Posteromedial dislocation of the ankle joint without fracture 2
- Multiligamentous ankle injury 2
- Osteochondral lesions of the talar dome 2
- Entrapment of tendons, such as the posterior tibial tendon, in the interosseous membrane or other structures 3, 4, 5
Importance of Early Diagnosis and Management
Early diagnosis and management of posterior dislocation of the ankle are crucial to prevent long-term complications and improve outcomes 4, 6, 5. Delayed treatment can lead to soft tissue contractures, malunited fractures, and avascular necrosis, making surgical correction more challenging 6.