What is the radiological appearance of a fracture calcaneus?

Radiological Appearance of Calcaneal Fractures

Calcaneal fractures typically present with characteristic radiological findings depending on the fracture type, with CT being the gold standard for detailed evaluation after initial radiographs to determine extent, displacement, comminution, and intra-articular extension.

Initial Radiographic Evaluation

• Standard radiographs are the first-line imaging modality for suspected calcaneal fractures, though they have limited sensitivity compared to advanced imaging 1
• Key radiographic measurements include:
  • Böhler angle (normally 20-40°) - often decreased or reversed in fractures 2
  • Varus angle - helps evaluate displacement 2
  • Harnroongroj angle - useful for assessing fragment displacement 2

CT Findings - The Gold Standard

• CT is the first-line imaging study after radiographs to determine extent, displacement, comminution, and intra-articular extension 1
• CT is particularly important for calcaneal fractures due to the complex anatomy and in high-impact polytrauma or complex comminuted injuries 1
• Multiplanar CT imaging is recommended to help direct preoperative planning 1
• CT allows detailed characterization of:
  • Fracture lines and patterns
  • Degree of comminution
  • Subtalar joint involvement
  • Fragment displacement 3

Classification of Calcaneal Fractures

Intra-articular Fractures (70-75% of cases)

• Result from axial loading producing shear and compression fracture lines 3
• Sanders classification (based on CT findings) is most commonly used 3:
  • Type I: Non-displaced fractures of the posterior facet
  • Type II: Displaced two-part fractures
  • Type III: Displaced three-part fractures
  • Type IV: Comminuted fractures 4
• Intra-articular fractures involving the subtalar joint show diffuse pain in the rearfoot 1

Extra-articular Fractures (25-30% of cases)

• Include all fractures that do not involve the posterior facet 3
• Avulsion fractures occur in reproducible locations due to the specific attachments of stabilizing ligaments 5

MRI Findings

• MRI allows visualization of bone marrow edema patterns, improving detection of fractures in cases of negative or inconclusive radiographs 1
• MRI is useful for detecting occult calcaneal fractures that may not be visible on initial radiographs 1
• MRI can identify associated soft tissue injuries, which are common with calcaneal fractures 1

Specific Radiographic Views

• Axial Harris-Beath view: Used for suspected calcaneal fractures to determine intra-articular extent 1
• Broden view: Supine flexed knee view with 30-45° internal rotation, useful for evaluating lateral process fractures of the talus 1

Pitfalls and Considerations

• Stress fractures of the calcaneus may not be visible on initial radiographs - symptoms often precede radiographic findings 1
• In cases of suspected stress fractures with negative radiographs, technetium bone scanning or MRI can be helpful 1
• Dual-energy CT has excellent performance in detecting bone marrow edema with 98% sensitivity and 93% specificity, potentially aiding in detection of radiographically occult fractures 1
• Soft tissue trauma, such as acute rupture of the plantar fascia, can cause heel pain with negative radiographs and bone scans 1

Complications Visible on Imaging

• Local inflammatory reactions at fixation points 2
• Thromboembolic complications 2
• Malunion or nonunion 6
• Post-traumatic arthritis of the subtalar joint 3