Courtesy: Dr Mette Andersen, Tromso, Norway

 

High Ankle Sprains (Syndesmotic Injuries): Evaluation & Management

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Overview

High ankle sprains involve injury to the distal tibiofibular syndesmosis and are frequently missed.

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Clinical Importance

Missed diagnosis may lead to:

• Delayed return to sport
• Chronic instability
• Soft tissue impingement
• Post-traumatic osteoarthritis

Nearly 80% of ankle osteoarthritis is post-traumatic

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Case Example

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Typical Scenario

• Athlete: Junior kickboxer
• Mechanism:
  • Hyper-dorsiflexion
  • External rotation
  • Axial loading

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Clinical Findings

• Positive squeeze test
• Tenderness:
  • Deltoid ligament
  • Interosseous membrane

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Imaging

• X-ray: Normal
• MRI findings:
  • AITFL injury
  • Interosseous membrane edema
  • No PITFL tear
  • No deltoid ligament injury
  • No diastasis

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Key Clinical Challenge

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Primary Objectives

• Avoid missed diagnosis
• Differentiate between:
  • Stable injuries
  • Unstable injuries

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Classification: West Point System

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Grade 1

• Partial AITFL tear
• Stable

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Grade 2 (Most Challenging)

• Complete AITFL rupture
• Partial interosseous ligament injury
• No diastasis on X-ray
• Possible subtle instability

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Grade 3

• Complete syndesmotic disruption
• Clear diastasis
• Unstable

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Epidemiology

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Common in

• Collision sports
• Skiing and hockey

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Incidence

• Approximately 20% of ankle sprains (MRI-detected)
• 13–18% in elite football

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Risk

• 14 times higher during matches compared to training

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Mechanism of Injury

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Typical Pattern

• External rotation combined with dorsiflexion
• Pronated ankle

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Key Factor

• Fixed forefoot increases severity

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Clinical Examination

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General Principle

No single test is definitive.

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Most Useful Tests

Squeeze Test

• Highest specificity

External Rotation Test

• Good sensitivity

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Less Reliable Tests

• Cotton test
• Fibular translation test

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Additional Finding

• Tenderness along the interosseous membrane
  • Greater proximal spread indicates more severe injury

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Imaging Modalities

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X-ray

• Detects fractures and gross diastasis
• May miss subtle instability

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CT Scan

• More sensitive than X-ray
• Requires bilateral comparison
• Static assessment

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Weight-Bearing CT

• Promising but limited availability

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Ultrasound

• Dynamic and cost-effective
• Operator dependent

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MRI (Best Imaging Modality)

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Accuracy

• Sensitivity and specificity: 95–100%

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Findings

• AITFL and PITFL injuries
• Interosseous ligament edema
• Associated intra-articular injuries

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Limitation

• Does not directly assess instability

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Important MRI Signs

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• AITFL discontinuity
• Interosseous ligament edema
• PITFL injury
• Posterior malleolar edema
• Periosteal stripping
• “Broken ring of fire” sign

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Associated Injuries

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Incidence

• Up to 50% of cases

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Types

• Loose bodies
• Cartilage lesions

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Gold Standard

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Arthroscopy

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Advantages

• Confirms instability
• Direct visualization
• Allows treatment of associated lesions

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Signs of Instability

• Syndesmotic widening > 2–3 mm
• Positive drive-through sign

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Indicators of Instability

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• Mechanism: dorsiflexion with external rotation
• Positive squeeze test or external rotation test
• Deltoid ligament injury
• PITFL injury on MRI

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Management

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Conservative Treatment (Stable Injuries)

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Protocol

• 3 weeks non-weight-bearing
• Followed by 3 weeks in a walking boot

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Grade 1 Injuries

• Faster recovery (approximately 3 weeks)

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Surgical Treatment (Unstable Injuries)

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Indications

• Grade 3 injuries
• Confirmed instability

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Options

• Syndesmotic screw fixation
• Suture button device
• With or without ligament repair

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Screw vs Suture Button

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Suture Button

• Better functional outcomes
• Lower malreduction rates
• Reduced long-term osteoarthritis risk

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Key Principle

Accurate reduction is more important than implant choice

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Complications

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• Joint stiffness
• Malreduction (up to 40%)
• Implant irritation
• Fractures (especially in osteoporotic bone)

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Rehabilitation Protocol

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• Boot immobilization: approximately 4 weeks
• Weight-bearing: after 2 weeks if tolerated
• Range of motion: begin at 10 days
• Proprioception training: from week 3
• Impact activities: from week 5

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Return to Sport

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• Conservative management: approximately 6 weeks
• Surgical management: 9–14 weeks

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Negative Predictors

• Grade 3 injury
• Age above 25 years
• Associated cartilage injury

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Key Takeaways

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• Maintain high suspicion for syndesmotic injury
• Use a combination of clinical tests and imaging
• MRI is essential but does not confirm instability
• Arthroscopy remains the gold standard
• Stable injuries are treated conservatively
• Unstable injuries require surgical stabilization
• Quality of reduction determines outcome

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Clinical Pearls

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• Most reliable clinical indicators:
  • Squeeze test
  • Local ligament tenderness
• Chronic cases:
  • Taping or stabilization tests may be useful
• Deltoid ligament:
  • Increasingly recognized as a key stabilizer
• Weight-bearing X-ray:
  • Limited role in detecting subtle instability