What is the initial emergency department workup for a 34-year-old female presenting with ankle edema and pain?

Initial Emergency Department Workup for 34-Year-Old Female with Ankle Edema and Pain

The initial emergency department workup for a 34-year-old female with ankle edema and pain should include application of the Ottawa Ankle Rules to determine the need for radiography, followed by appropriate physical examination to assess for ligamentous injury if radiographs are negative. 1

Initial Assessment

Ottawa Ankle Rules

• Apply the Ottawa Ankle Rules to determine need for radiography based on:
  • Inability to bear weight immediately after injury or inability to take 4 steps in the emergency department 1
  • Point tenderness over the medial malleolus, posterior edge or inferior tip of lateral malleolus, talus, or calcaneus 1
• The Ottawa Ankle Rules have high sensitivity (86-99%) but variable specificity (25-46%) for detecting fractures 1
• Following these rules can reduce unnecessary radiographs in approximately 30-40% of cases 1, 2

Physical Examination

• Assess for:
  • Distribution of edema (unilateral vs. bilateral) 3
  • Presence of hematoma (suggests ligament rupture) 1
  • Pain on palpation around distal fibula (suggests lateral ligament injury) 1
  • Anterior drawer test (positive test suggests anterior talofibular ligament injury) 1
  • Crossed-leg test (positive test suggests high ankle/syndesmotic sprain) 1
  • Neurovascular status of the foot 1

Diagnostic Imaging

Initial Radiography

• If Ottawa Ankle Rules are positive, obtain ankle radiographs including:
  • Anteroposterior view
  • Lateral view
  • Mortise view (15-20 degrees internal rotation) 1
• Radiographs can identify:
  • Fractures
  • Osteoarthritis
  • Joint effusions
  • Ossific fragments (indicating ligamentous injury) 1

Additional Imaging (if indicated)

• If radiographs are negative but pain persists for more than 1 week:
  • MRI without IV contrast or CT without IV contrast may be appropriate 1
• If radiographs are negative but physical exam suggests ligamentous injury:
  • MRI without IV contrast is the preferred next study 1
  • Alternatively, stress radiographs may be considered 1

Laboratory Testing

• Consider basic laboratory tests if systemic cause of edema is suspected:
  • Complete blood count
  • C-reactive protein and erythrocyte sedimentation rate (if infection or inflammation suspected)
  • Basic metabolic panel 4

Special Considerations

Differential Diagnosis for Ankle Edema

• Traumatic causes:
  • Ankle sprain (lateral, medial, or syndesmotic)
  • Fracture (malleolar, talar, calcaneal)
  • Achilles tendon injury 1, 5
• Non-traumatic causes:
  • Systemic illness (heart failure, liver disease, thyroid disorder)
  • Local conditions (infection, venous thrombosis)
  • Medication side effects 3

Grading of Ankle Sprains

• Grade I: Mild sprain with minimal functional loss
• Grade II: Moderate sprain with partial ligament tear
• Grade III: Severe sprain with complete ligament tear 1

Common Pitfalls

• Failing to apply Ottawa Ankle Rules appropriately, leading to unnecessary radiographs 1, 2
• Overlooking syndesmotic injuries, which require different management than lateral ankle sprains 1
• Premature assessment of ligamentous injuries (optimal assessment is 4-5 days post-injury when swelling has decreased) 1
• Focusing only on traumatic causes and missing systemic causes of ankle edema 3
• Inadequate pain management (both NSAIDs and acetaminophen can be effective) 6

By following this systematic approach, emergency physicians can efficiently evaluate ankle edema and pain, appropriately utilize imaging resources, and develop an effective treatment plan based on accurate diagnosis.