In an adult with foot pain and possible trauma, what does widening between the calcaneus and talus on a lateral foot X‑ray indicate and how should it be initially managed?

Widening Between Calcaneus and Talus on Lateral Foot X-ray

Widening between the calcaneus and talus on a lateral foot X-ray in an adult with foot pain and possible trauma most likely indicates subtalar joint dislocation or disruption, which requires urgent orthopedic evaluation and prompt closed reduction to prevent neurovascular compromise and long-term complications.

Primary Diagnostic Considerations

Subtalar Dislocation

• Widening of the talocalcaneal joint space represents simultaneous dislocation of both the talonavicular and talocalcaneal joints, typically caused by high-mechanism injuries 1
• Lateral subtalar dislocations (86.96% of cases) result from violent eversional forces that drive the talar head medially while displacing the calcaneus and rest of the foot laterally 2, 3
• Clinical presentation includes hindfoot pain, swelling, deformity, and often a history of significant trauma such as falls or motor vehicle accidents 1, 3

Associated Radiographic Signs

• The "double-density sign" on lateral radiographs appears in 47.83% of calcaneal fracture-dislocations and indicates overlapping of displaced bones 3
• Varus tilt of the talus within the ankle mortise is evident in 39.13% of cases and suggests disruption of the subtalar relationship 3
• Look for associated fractures, as they are more common with lateral dislocations than medial dislocations and may obstruct closed reduction 2

Initial Imaging Protocol

Standard Radiographic Evaluation

• Three-view foot radiographs (anteroposterior, lateral, and oblique) are the appropriate initial imaging study for acute foot trauma 4
• Weight-bearing views should be obtained when possible to assess joint stability and alignment, though this may not be feasible in acute trauma 4
• The lateral view is critical for identifying widening between the talus and calcaneus 4

Advanced Imaging Indications

• CT without IV contrast is excellent for evaluating the extent of displacement, comminution, and associated fractures that may complicate reduction 5
• CT is particularly valuable when radiographs show complex fracture patterns or when closed reduction fails 4
• MRI without IV contrast is the most sensitive modality for detecting associated soft tissue injuries, including ligamentous disruptions and bone marrow edema 5

Immediate Management Algorithm

Emergency Department Management

1. Perform immediate closed reduction under procedural sedation for the majority of closed subtalar dislocations to avoid soft-tissue or neurovascular compromise 1, 2
2. Avoid manipulation prior to radiographs only if there is neurovascular deficit or critical skin injury 4
3. Post-reduction radiographs and CT are essential to confirm anatomic alignment and identify occult fractures 4, 5

Indications for Open Reduction

• Open reduction is required when closed reduction fails, particularly with entrapment of the posterior tibial tendon or obstructing fracture fragments 2
• Open dislocations have significantly worse outcomes and require urgent surgical debridement and reduction 1
• Associated intra-articular fractures (Sanders type II in 65.22% and type III in 30.43% of cases) often necessitate open reduction and internal fixation 3

Post-Reduction Management

Immobilization

• A short period of immobilization (typically 4-6 weeks) limits loss of subtalar range of motion while allowing soft tissue healing 2
• Cast immobilization or fixed-ankle walker-type devices are appropriate 4
• Early mobilization after adequate healing prevents stiffness 2

Follow-up Imaging

• Serial radiographs are necessary to monitor for loss of reduction 4
• Consider delayed MRI (4-5 days post-injury) if persistent symptoms suggest occult soft tissue injuries, as sensitivity and specificity of physical examination are optimized at this timeframe 5

Critical Pitfalls to Avoid

Missed Diagnosis

• Subtalar dislocations can be misdiagnosed as simple ankle sprains, leading to delayed treatment and poor outcomes including post-traumatic arthritis 3
• One case series reported a misdiagnosed patient who developed early post-traumatic arthritis requiring future subtalar arthrodesis 3
• Maintain high clinical suspicion when hindfoot deformity, severe swelling, or abnormal talar positioning is present 1, 3

Delayed Reduction

• Prompt closed reduction is essential—delays increase the risk of soft tissue compromise, neurovascular injury, and difficulty achieving reduction 1, 2
• The longer the dislocation remains unreduced, the higher the likelihood of requiring open reduction 2

Long-Term Complications

Expected Sequelae

• Avascular necrosis of the talus and navicular can occur following subtalar dislocation 1, 2
• Post-traumatic subtalar arthritis is common and may ultimately require triple arthrodesis 1, 2
• Subtalar instability and chronic pain affect functional outcomes 1
• Patients treated surgically (86.96% in one series) generally achieve satisfactory outcomes when reduction is timely and anatomic 3

Prognostic Factors

• Closed injuries managed with prompt reduction have better outcomes than open dislocations 1
• Associated fractures worsen prognosis and increase the need for surgical intervention 2, 3
• Conservative treatment has poor clinical outcomes and should be avoided 3