Episode 172.0 – Ankle Sprains

Show Notes

Background

• Among most common injuries evaluated in ED
• A sprain is an injury to 1 or more ligaments about the ankle joint
• Highest rate among teenagers and young adults
  • Higher incidence among women than men
• Almost a half are sustained during sports
• Greatest risk factor is a history of prior ankle sprain

Anatomy

• Bone: Distal tibia and fibula over the talus → constitutes the ankle mortise
• Aside from malleoli, ligament complexes hold joint together
  • Medial deltoid ligament
  • Lateral ligament complex
    • Anterior talofibular ligament
      • Most commonly injured
      • Weakest
      • 85% of all ankle sprains 
    • Posterior talofibular ligament
    • Calcaneofibular ligament
  • Syndesmosis

Mechanism of Injury

• Lateral ankle sprains 
  • Most common among athletes
  • ATFL most commonly injured
    • Combined with CFL in 20% of injuries
  • 2/2 inversion injuries
• Medial ankle sprains
  • Less common than lateral because ligaments stronger and mechanism less frequent
    • More likely to suffer avulsion fracture of medial malleolus than injure medial ligament
  • 2/2 eversion +/- forced external rotation
  • Typically landing on pronated foot -> external rotation
• High Ankle sprains
  • Syndesmotic injury
  • More common in collision sports (football, soccer, etc)

• Grade I
  • Mild
  • Stretch without “macroscopic” tearing
  • Minimal swelling / tenderness
  • No instability
  • No disability associated with injury
•     Grade II
  • Moderate
  • Partial tear of ligament
  • Moderate swelling / tenderness
  • Some instability and loss of ROM
  • Difficulty ambulating / bearing weight
•     Grade III
  • Severe
  • Complete rupture of ligaments
  • Extensive swelling / ecchymosis / tenderness
  • Mechanical instability on exam
  • Inability to bear weight

Examination

•     Beyond visual inspection for swelling, ecchymoses, abrasions, or lacerations
  • Palpation 
  • Pain when palpating ligament is poorly specific but may indicate injury to structure
  • Check sites for Ottawa ankle rules to evaluate if there may be an associated fracture with injury
    • Posterior edge or tip of lateral malleolus (6 cm)
    • Posterior edger or tip of medial malleolus (6 cm)
    • Base of fifth metatarsal
    • Navicular bone
  • Acute ATFL rupture / Grade III Sprain
    • 90% chance of this injury if hematoma and localized tenderness with palpation present on exam over this ligament 
    • Anterior drawer test
      • Assess for anterior subluxation of talus from the tibia
        • Ankle in relaxed position, distal extremity is stabilized with one hand while the other cups the heel to apply anterior force
      • Compare to contralateral side
      • Difficult to determine if there is an acute rupture at this point and may be more easily diagnosed in subacute phase (4-5 days after injury)
      • Ability to perform exam adequately limited by pain, swelling and potential muscle spasm
    • Talar tilt test
      • If applying inversion force to ankle and there is excessive mobility → calcaneofibular ligament
    • Thompson test
      • Can be performed if there is concern for concomitant Achilles tendon injury 
  • Do not miss a Maisonneuve fracture by palpating proximally about the fibular ahead as forces may be transmitted through the syndesmosis 
    • Squeeze test – pressure just proximal to ankle
      • If elicits pain → concern for syndesmotic injury

Diagnostics

•     X-rays indicated if unable to rule out using Ottawa Ankle Rules
  • Sn (Up to 99.6) (one of the best validated tools we use in the ER)
  • May have trouble applying rule if there is question of patients ability to sense pain (diabetic neuropathy), in which case obtain radiographs

Treatments

•     RICE
  • Crutch train so they can be weight bearing a tolerated