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Ankle Instability

  • Recurrent ankle sprains occurring primarily from an inversion stress on a plantarflexed ankle, which lead to chronic ankle pain and instability
  • Divided into 2 types:
    • Functional instability:
      • Pain causes ankle to be unstable.
      • Feeling of ankle giving way
      • Neuromuscular deficit
    • True mechanical instability:
      • Frank insufficiency of ligaments
      • Physiologic ROM is exceeded.
      • Positive anterior drawer or talar tilt test
General Prevention
  • Treat initial ankle sprains aggressively using:
    • Activity modification
    • Bracing
    • Functional rehabilitation program
  • Ankle sprains account for as many as 40% of all athletic injuries .
  • 27,000 ankle sprains occur each day in the United States.
  • Symptomatic ankle instability will develop in up to 20% of patients after an inversion sprain of the lateral ankle ligaments.
High in soccer and basketball players
Risk Factors
  • History of previous sprain (most common risk factor)
  • Connective-tissue disorders
  • Cavovarus foot alignment
  • Complex causes of functional instability:
    • Neural: Proprioception, reflexes, muscle reaction time
    • Muscular: Strength, power, endurance
    • Mechanical: Lateral ligamentous laxity
  • Ankle sprains cause sequential disruption of:
    • Anterolateral joint capsule
    • ATFL
    • CFL
  • Primary static restraints to ankle inversion injury:
    • ATFL:
      • Most commonly injured ankle ligament
      • Primary restraint to inversion with ankle plantarflexed
      • Torn in inversion, plantarflexion, and internal rotation
    • CFL:
      • Stabilizes ankle and subtalar joints
      • Resists inversion with ankle dorsiflexed
      • Tears in inversion and dorsiflexion
  • Primary dynamic restraints:
    • Peroneal tendons
  • Key anatomy:
    • ATFL:
      • Originates 1 cm proximal to tip of lateral malleolus
      • Inserts into talus 18 mm superior to subtalar joint, coursing anteriorly at a 90° angle to fibula
      • 7 mm wide, 10 mm long
      • Intimately associated with joint capsule
    • CFL:
      • Originates adjacent to the ATFL, 8 mm proximal to tip of fibula
      • Courses at a 30° angle to the fibula, heading posteriorly and distally to insert on the calcaneus 13 mm distal to subtalar joint
      • Extracapsular: Floor of peroneal sheath
    • Posterior talofibular ligament: Rarely injured except with ankle dislocations
Associated Conditions
Connective-tissue disorders: Ehlers-Danlos
  • Must differentiate functional from mechanical instability.
  • 30% of simple ankle sprains result in residual symptoms with peroneal weakness (functional instability).
Signs and Symptoms
Recurrent ankle pain and swelling
  • Recurrent sprains with minimal trauma
  • Subjective feeling of ankle giving way
  • Repeated episodes of instability with asymptomatic periods between episodes
Physical Exam
  • Assess hindfoot alignment.
  • Evaluate gait.
  • Neurovascular examination: Increased superficial peroneal nerve injuries in patients with recurrent ankle sprains
  • Palpate peroneal tendons.
  • Assess ankle ROM.
    • Crepitus and pain with ROM may be indicative of cartilaginous injury.
  • Assess subtalar motion.
    • Rigidity may suggest tarsal coalition.
  • Assess subtalar stability.
    • Assess CFL integrity.
    • Dorsiflex ankle and apply inversion force to calcaneus.
    • Medial translation of calcaneus is indicative of subtalar instability.
  • Evaluate for mechanical instability.
    • Anterior drawer test:
      • Evaluates ATFL
      • Position ankle in neutral and apply anterolateral force to heel.
      • Positive test: >10 mm of anterior translation on involved side, >3 mm of anterior translation greater than on uninvolved side; confirm with lateral stress radiograph.
    • Talar tilt test:
      • Evaluates CFL
      • Patient seated, ankle neutral
      • Apply inversion force to hindfoot and midfoot as a unit.
      • Do not allow forefoot to rotate medially.
      • Positive test: Talar tilt >9° total, talar tilt 3° more on involved than uninvolved side; confirm on stress mortise radiograph.
  • Lateral and mortise radiographs:
    • Posttraumatic changes:
      • Tibial marginal osteophytes
      • Talar exostoses (at ATFL insertion)
      • Osteochondral lesions of talus
      • Os subfibulare
  • Mortise and lateral stress radiographs:
    • Anterior translation (assesses ATFL):
      • Measured on lateral stress radiograph
      • Perpendicular distance between posterior edge of tibial articular surface and talus
      • Anterior translation 5 mm more than other side or 10 mm absolute is indicative of mechanical instability.
    • Talar tilt (assesses CFL):
      • Measured on mortise stress view
      • Angle between tibial and talar surfaces
      • Talar tilt angle 3° more than the other side or 10° absolute is indicative of mechanical instability.
Differential Diagnosis
  • Ankle pain may be associated with ankle instability.
  • Other causes of ankle pain include (2,5):
    • Intra-articular fibrosis/synovitis
    • Talus OATS
    • Peroneal tendon tears
    • Peroneal tendon subluxation
    • Lateral process of talus fracture
General Measures
  • Initial treatment for ankle instability is nonoperative.
    • RICE protocol
    • Ankle brace:
      • Moderate to severe sprains may be braced for 6 months to allow return to sports.
    • Functional rehabilitation
    • Residual lateral ankle pain and functional instability most often are secondary to inadequate rehabilitation.
  • Restrict sports until:
    • Rehabilitation program is completed.
    • Strength and ROM are normal.
    • Patient is able to perform sport-specific tasks (cutting, jumping).
  • Functional bracing or taping during return to athletics may help prevent recurrence.
    • Braces do not interfere with performance.
Special Therapy
Physical Therapy
  • Should emphasize:
    • ROM, concentric and eccentric muscle strengthening
    • Endurance training of peroneals
    • Proprioception
    • Tilt-board exercises
  • Indications for surgery:
    • Persistent instability after a functional rehabilitation program
    • Extreme laxity
    • Recurrent sprains with normal activities
    • Instability with sports despite bracing/taping
  • Surgical techniques:
    • Anatomic repair:
      • Best results for patients with good-quality soft tissues
      • Benefits: Restores normal anatomy, preserves subtalar motion, preserves peroneals (dynamic stabilizers)
      • Contraindications: Connective-tissue disorder (Ehlers-Danlos), failed previous surgery, severely attenuated tissue (>10 years of instability)
      • Brostrom repair : Direct late repair, torn ends of ATFL shortened and repaired; sometimes CFL imbrication is necessary
      • Gould modification : Immobilization and reattachment of inferior extensor retinaculum to fibula after imbrication of ATFL and CFL; provides additional stability
      • Combination of Brostrom and Gould technique is the gold standard, with 90% success rate .
    • Reconstruction (Chrisman-Snook, Evans):
      • Indications: Patient with poor-quality soft tissue (ligaments are attenuated), salvage for a failed Brostrom procedure, obesity/high-demand patient
      • Benefits: Increased strength of repair
      • Problems: Nonanatomic reconstruction, loss of talocrural and subtalar motion, adjacent peroneal nerve injury
      • Chrisman-Snook reconstruction : Split peroneus brevis at its attachment to base of 5th metatarsal; harvest proximal portion of split peroneus brevis and weave it anterior to posterior through a drill hole in fibula; then weave it posterior to anterior through a calcaneal bone tunnel; suture it back to itself.
      • Evans reconstruction : Harvest proximal portion of peroneus brevis; weave it anterior to posterior through a fibular drill hole; does not address subtalar instability
    • Realignment procedures: Hindfoot varus calcaneal osteotomy can be performed in conjunction with repair or reconstruction.
  • Postoperatively:
    • Cast in eversion for 6 weeks
    • Then switch to removable brace
    • Physical therapy for 3 months
    • Protective brace for at least 6 months
  • High success rate regardless of anatomic repair or tenodesis procedure
  • Predictors of poor outcome after surgery:
    • 10 years of symptoms
    • Ankle osteoarthritis
    • Joint hypermobility
  • Highest percentage occur in nonanatomic reconstruction procedures
    • Loss of subtalar and talocrural motion
    • Peroneal nerve injury
    • Tendon failure: Tendons are stiffer and have less strain to failure than ligaments.
718.87 Ankle instability
Patient Teaching
Modify activities until appropriate rehabilitation program is completed.
Brace may prevent recurrence during athletics.
Q: Does the patient have functional or mechanical instability?
A: Check anterior drawer and talar tilt test to document presence or absence of mechanical instability.
Q: What are the initial treatment recommendations for a patient presenting with functional ankle instability?
A: Activity modification, ankle brace, functional rehabilitation program focusing on proprioception and endurance training of peroneals.
Q: What is the gold standard initial surgery for mechanical ankle instability in a healthy athlete?
A: An anatomic repair procedure such as the Brostrom repair with Gould modification.

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