What is Weber's classification of ankle injuries on X-ray?

Weber's Classification of Ankle Injuries on X-ray

Weber's classification system categorizes ankle fractures based on the level of the fibular fracture in relation to the syndesmosis, which directly correlates with syndesmotic stability and patient outcomes.

Weber Classification System

The Weber classification (also known as the Danis-Weber classification) divides ankle fractures into three types:

• Type A: Fracture of the fibula below the level of the syndesmosis

  • Typically stable injuries
  • Syndesmotic ligaments remain intact
  • Good prognosis with conservative management

• Type B: Fracture of the fibula at the level of the syndesmosis

  • May have partial syndesmotic disruption
  • Stability varies and requires assessment
  • May require surgical intervention depending on stability

• Type C: Fracture of the fibula above the level of the syndesmosis

  • Associated with syndesmotic disruption
  • Typically unstable injuries
  • Often requires surgical fixation

Clinical Significance and Limitations

• Weber classification has prognostic value for unimalleolar fractures but is less predictive for bimalleolar and trimalleolar fractures 1
• Weber C fractures demonstrate significantly greater degrees of syndesmotic instability than Weber B fractures 2
• The classification does not account for:
  • Number of malleoli involved (which is a significant predictor of outcome)
  • Initial degree of displacement
  • Patient age (older patients tend to have poorer outcomes)

Assessment of Syndesmotic Stability

For Weber B fractures, additional assessment is often needed to determine stability:

• Weight-bearing radiographs: Can help determine fracture stability and guide treatment decisions 3
• Stress tests:
  • Lateral stress test appears superior to external rotation stress test for detecting syndesmotic instability 4
  • Fibular hook traction test can be used intraoperatively to classify syndesmosis stability 2

Radiographic Measurements

Several measurements can be used to assess syndesmotic injury on X-ray:

• Tibiofibular clear space (TFCS): Distance between the medial border of the fibula and the lateral border of the posterior tibia
• Tibiofibular overlap (TFO): Overlap between the anterior tibia and fibula
• Medial clear space (MCS): Distance between the medial malleolus and the talus

However, these measurements have limitations, as they do not always correlate with syndesmotic injury when compared to MRI findings 5.

Advanced Imaging

When radiographic findings are inconclusive:

• CT: Useful for determining fracture extent, displacement, comminution, and intra-articular extension 6
• MRI: Reference standard for ligamentous injury assessment and stability evaluation, particularly important in athletes 6

Common Pitfalls

• Relying solely on the Weber classification without assessing stability can lead to missed syndesmotic injuries
• Overlooking the number of malleoli involved, which is a stronger predictor of outcome than the level of fibular fracture alone 1
• Failing to recognize that Weber B fractures have variable stability and require additional assessment
• Not considering patient factors like age that influence outcomes

Weber's classification provides a foundation for understanding ankle fracture patterns, but comprehensive assessment should include stability evaluation and consideration of additional factors that affect prognosis and treatment decisions.