What imaging is needed for a deltoid ligament injury (DTI) to the ankle?

Imaging for Deltoid Ligament Injury (DTI) to the Ankle

For suspected deltoid ligament injury to the ankle, stress radiographs (gravity stress view) are the most appropriate initial imaging modality, with MRI indicated when radiographs are negative but clinical suspicion remains high. 1

Initial Assessment and Imaging Algorithm

Step 1: Clinical Assessment

• Apply Ottawa Ankle Rules to determine need for imaging:
  • Check for point tenderness over the malleoli
  • Assess ability to bear weight and walk 4 steps immediately after injury
  • Evaluate for pain on palpation at the base of the fifth metatarsal or navicular bone

Step 2: Initial Imaging

1. Standard Radiographs:

   • Weight-bearing anteroposterior (AP), lateral, and mortise views
   • Look for fractures and medial clear space widening

2. Stress Radiographs:

   • Gravity stress view is more reliable than manual stress view for evaluating deltoid ligament disruption 1
   • A medial clear space measurement ≥5.5 mm on injury radiographs correlates with complete deltoid ligament injury 2
   • Medial clear space >4 mm correlates with disruption of both deltoid and tibiofibular ligaments 3

Step 3: Advanced Imaging (if needed)

• MRI: Indicated when radiographs are negative but clinical suspicion remains high 4

  • Excellent for evaluating both superficial and deep components of the deltoid ligament
  • Can identify associated injuries (syndesmosis tears, lateral collateral ligament tears) 5

• Ultrasonography: Alternative to stress views

  • Has shown 100% sensitivity and specificity in diagnosing medial deltoid rupture compared to arthrogram 6
  • Avoids ionizing radiation and is less invasive

Deltoid Ligament Injury Patterns

The deltoid ligament has 5 components:

• 3 superficial components
• 2 deep components

Common injury patterns:

• Combined superficial and deep tears (58.3%) 5
• Superficial component tears only (16.7%) 5
• Deep component tears only (11.1%) 5

Most common tear locations:

• Superficial deltoid: proximal attachments (94%) 5
• Deep anterior tibiotalar ligament: proximal attachment (91.7%) 5
• Deep posterior tibiotalar ligament: distal attachment (82.6%) 5

Associated Injuries to Evaluate

When assessing deltoid ligament injuries, look for:

• Ankle fractures (63.9% association) 5
• Syndesmosis tears (55.6% association) 5
• Lateral collateral ligament complex tears (44.4% association) 5
• Deltoid ligament injuries are also common (72%) in patients with chronic lateral ankle instability 7

Clinical Pitfalls and Caveats

1. Radiographic measurements alone are unreliable:

   • Tibiofibular clear space and overlap measurements on radiographs do not reliably correlate with syndesmotic injury on MRI 3
   • Clinical correlation is essential

2. Complete vs. Partial Tears:

   • Complete deltoid ligament tears correlate with medial clear space ≥5.5 mm
   • Partial tears typically show medial clear space between 4.0-5.0 mm 2

3. Occult Injuries:

   • Deltoid ligament injuries can occur in patients with lateral ankle instability without medial ankle pain 7
   • Consider comprehensive ligament assessment even with primarily lateral symptoms

4. Follow-up Imaging:

   • For persistent symptoms despite appropriate treatment, follow-up MRI may be necessary to evaluate healing and identify complications

By following this imaging algorithm, you can accurately diagnose deltoid ligament injuries and associated pathologies to guide appropriate treatment decisions.