What is Ankle Instability?
Ankle Instability is characterised by the feeling of ankle ready to give way.
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Basics
Description
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Recurrent ankle sprains occurring primarily from an inversion stress on a plantarflexed ankle, which lead to chronic ankle pain and instability
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Divided into 2 types:
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Functional instability:
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Pain causes ankle to be unstable.
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Feeling of ankle giving way
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Neuromuscular deficit
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True mechanical instability:
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Frank insufficiency of ligaments
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Physiologic ROM is exceeded.
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Positive anterior drawer or talar tilt test
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General Prevention
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Treat initial ankle sprains aggressively using:
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Activity modification
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Bracing
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Functional rehabilitation program
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Epidemiology
Incidence
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Ankle sprains account for as many as 40% of all athletic injuries .
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27,000 ankle sprains occur each day in the United States.
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Symptomatic ankle instability will develop in up to 20% of patients after an inversion sprain of the lateral ankle ligaments.
Prevalence
High in soccer and basketball players
Risk Factors
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History of previous sprain (most common risk factor)
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Connective-tissue disorders
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Cavovarus foot alignment
Etiology
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Complex causes of functional instability:
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Neural: Proprioception, reflexes, muscle reaction time
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Muscular: Strength, power, endurance
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Mechanical: Lateral ligamentous laxity
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Ankle sprains cause sequential disruption of:
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Anterolateral joint capsule
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ATFL
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CFL
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Primary static restraints to ankle inversion injury:
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ATFL:
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Most commonly injured ankle ligament
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Primary restraint to inversion with ankle plantarflexed
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Torn in inversion, plantarflexion, and internal rotation
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CFL:
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Stabilizes ankle and subtalar joints
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Resists inversion with ankle dorsiflexed
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Tears in inversion and dorsiflexion
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Primary dynamic restraints:
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Peroneal tendons
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Key anatomy:
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ATFL:
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Originates 1 cm proximal to tip of lateral malleolus
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Inserts into talus 18 mm superior to subtalar joint, coursing anteriorly at a 90° angle to fibula
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7 mm wide, 10 mm long
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Intimately associated with joint capsule
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CFL:
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Originates adjacent to the ATFL, 8 mm proximal to tip of fibula
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Courses at a 30° angle to the fibula, heading posteriorly and distally to insert on the calcaneus 13 mm distal to subtalar joint
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Extracapsular: Floor of peroneal sheath
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Posterior talofibular ligament: Rarely injured except with ankle dislocations
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Associated Conditions
Connective-tissue disorders: Ehlers-Danlos
Diagnosis
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Must differentiate functional from mechanical instability.
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30% of simple ankle sprains result in residual symptoms with peroneal weakness (functional instability).
Signs and Symptoms
Recurrent ankle pain and swelling
History
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Recurrent sprains with minimal trauma
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Subjective feeling of ankle giving way
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Repeated episodes of instability with asymptomatic periods between episodes
Physical Exam
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Assess hindfoot alignment.
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Evaluate gait.
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Neurovascular examination: Increased superficial peroneal nerve injuries in patients with recurrent ankle sprains
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Palpate peroneal tendons.
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Assess ankle ROM.
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Crepitus and pain with ROM may be indicative of cartilaginous injury.
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Assess subtalar motion.
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Rigidity may suggest tarsal coalition.
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Assess subtalar stability.
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Assess CFL integrity.
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Dorsiflex ankle and apply inversion force to calcaneus.
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Medial translation of calcaneus is indicative of subtalar instability.
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Evaluate for mechanical instability.
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Anterior drawer test:
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Evaluates ATFL
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Position ankle in neutral and apply anterolateral force to heel.
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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.
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Talar tilt test:
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Evaluates CFL
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Patient seated, ankle neutral
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Apply inversion force to hindfoot and midfoot as a unit.
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Do not allow forefoot to rotate medially.
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Positive test: Talar tilt >9° total, talar tilt 3° more on involved than uninvolved side; confirm on stress mortise radiograph.
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Tests
Imaging
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Lateral and mortise radiographs:
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Posttraumatic changes:
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Tibial marginal osteophytes
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Talar exostoses (at ATFL insertion)
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Osteochondral lesions of talus
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Os subfibulare
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Mortise and lateral stress radiographs:
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Anterior translation (assesses ATFL):
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Measured on lateral stress radiograph
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Perpendicular distance between posterior edge of tibial articular surface and talus
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Anterior translation 5 mm more than other side or 10 mm absolute is indicative of mechanical instability.
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Talar tilt (assesses CFL):
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Measured on mortise stress view
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Angle between tibial and talar surfaces
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Talar tilt angle 3° more than the other side or 10° absolute is indicative of mechanical instability.
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Differential Diagnosis
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Ankle pain may be associated with ankle instability.
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Other causes of ankle pain include (2,5):
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Intra-articular fibrosis/synovitis
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Talus OATS
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Peroneal tendon tears
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Peroneal tendon subluxation
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Lateral process of talus fracture
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Treatment
General Measures
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Initial treatment for ankle instability is nonoperative.
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RICE protocol
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Ankle brace:
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Moderate to severe sprains may be braced for 6 months to allow return to sports.
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Functional rehabilitation
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Residual lateral ankle pain and functional instability most often are secondary to inadequate rehabilitation.
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Activity
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Restrict sports until:
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Rehabilitation program is completed.
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Strength and ROM are normal.
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Patient is able to perform sport-specific tasks (cutting, jumping).
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Functional bracing or taping during return to athletics may help prevent recurrence.
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Braces do not interfere with performance.
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Special Therapy
Physical Therapy
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Should emphasize:
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ROM, concentric and eccentric muscle strengthening
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Endurance training of peroneals
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Proprioception
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Tilt-board exercises
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Surgery
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Indications for surgery:
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Persistent instability after a functional rehabilitation program
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Extreme laxity
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Recurrent sprains with normal activities
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Instability with sports despite bracing/taping
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Surgical techniques:
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Anatomic repair:
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Best results for patients with good-quality soft tissues
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Benefits: Restores normal anatomy, preserves subtalar motion, preserves peroneals (dynamic stabilizers)
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Contraindications: Connective-tissue disorder (Ehlers-Danlos), failed previous surgery, severely attenuated tissue (>10 years of instability)
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Brostrom repair : Direct late repair, torn ends of ATFL shortened and repaired; sometimes CFL imbrication is necessary
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Gould modification : Immobilization and reattachment of inferior extensor retinaculum to fibula after imbrication of ATFL and CFL; provides additional stability
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Combination of Brostrom and Gould technique is the gold standard, with 90% success rate .
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Reconstruction (Chrisman-Snook, Evans):
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Indications: Patient with poor-quality soft tissue (ligaments are attenuated), salvage for a failed Brostrom procedure, obesity/high-demand patient
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Benefits: Increased strength of repair
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Problems: Nonanatomic reconstruction, loss of talocrural and subtalar motion, adjacent peroneal nerve injury
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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.
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Evans reconstruction : Harvest proximal portion of peroneus brevis; weave it anterior to posterior through a fibular drill hole; does not address subtalar instability
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Realignment procedures: Hindfoot varus calcaneal osteotomy can be performed in conjunction with repair or reconstruction.
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Follow-up
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Postoperatively:
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Cast in eversion for 6 weeks
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Then switch to removable brace
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Physical therapy for 3 months
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Protective brace for at least 6 months
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Prognosis
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High success rate regardless of anatomic repair or tenodesis procedure
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Predictors of poor outcome after surgery:
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10 years of symptoms
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Ankle osteoarthritis
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Joint hypermobility
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Complications
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Highest percentage occur in nonanatomic reconstruction procedures
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Loss of subtalar and talocrural motion
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Peroneal nerve injury
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Tendon failure: Tendons are stiffer and have less strain to failure than ligaments.
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Miscellaneous
Codes
ICD9-CM
718.87 Ankle instability
Patient Teaching
Activity
Modify activities until appropriate rehabilitation program is completed.
Prevention
Brace may prevent recurrence during athletics.
FAQ
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.