Syndesmodial Injury of the Lower Leg

Ovid: 5-Minute Sports Medicine Consult, The

Syndesmodial Injury of the Lower Leg
Delmas J. Bolin
Lauren Wood
  • Involves disruption of ligaments supporting the integrity of the mortise joint
  • Associated with prolonged symptoms of pain and dysfunction
  • Relevant injured structures can include anterior tibiofibular, posterior tibiofibular and transverse tibiofibular ligaments, interosseous membrane, and interosseous ligament, which serve to prevent lateral displacement of distal fibula during weight bearing
  • Synonym(s): High ankle sprain
  • Mechanism of injury involves sudden, forceful external rotation of the dorsiflexed ankle.
  • The talus is pressed against the fibula, opening the distal tibiofibular articulation and rupturing the tibiofibular syndesmosis.
  • 10–20% of all ankle sprains
  • Higher percentage of ankle sprains involve the syndesmosis when occurring in collision sports such as football, rugby, and lacrosse.
Risk Factors
  • Collision sports are at higher risk:
    • Football
    • Rugby
    • Lacrosse
  • Sports that immobilize the foot in a high ankle shoe or boot:
    • Hockey
    • Slalom skiing; catching inner ski on gate
  • Sports played on turf, eg, soccer
Commonly Associated Conditions
  • Deltoid ligament tear
  • Fibular or medial malleolar fracture
  • Heterotopic ossification or synchondrosis of the syndesmosis in 25–100% of cases
  • Tibiofibular synostosis resulting in prolonged pain and chronic disability
  • Longer healing time and more missed practices
  • Occult talar dome fracture
  • Patient is often unable to adequately or completely describe mechanism; patients commonly report an inversion mechanism.
  • Focus history on mechanism of injury; raise index of suspicion with history of forceful external rotation, hyperdorsiflexion, or hyperplantarflexion.
  • Examples of common mechanisms include soccer (player tackling ball), football (player prone, has foot stepped on, leading to forceful external rotation), and skiing (slalom skiers, catch ski on gate)
  • Pain is usually between anterior distal tibia and fibula; also posteromedially at ankle joint.
  • Patients complain of pain with weight bearing, pushing off, or with external rotation.
Physical Exam
  • Less swelling than anticipated with severe lateral ankle sprain
  • Palpation of the tibia and fibula helpful to rule out fracture:
    • Anterior joint line and anterior syndesmosis are often tender.
  • Squeeze test: Compression above mid-calf produces distal pain in the anterior ankle joint (syndesmosis).
  • External rotation test: Distal lower leg is stabilized with ankle in neutral position while mediolateral force/external rotation of the foot is performed. Positive test noted by pain and/or increased rotation relative to unaffected side.
  • Push-off test: Push-off/heel raise on affected side may be weak or absent.
  • Fibular translation (drawer) test: Increased translation of fibula from anterior to posterior or loss of firm end-point relative to uninjured side
  • Stabilization test: Distal syndesmosis is stabilized with athletic tape and assess if symptoms are decreased with running and jumping.
  • Cotton test: Increased translation or pain with translation of talus from medial to lateral (may indicate deltoid ligament tear)
  • Crossed-leg test: Pain at syndesmosis with gentle pressure exerted on the medial side of the knee while resting the mid-tibia of affected leg on uninjured knee
  • Evaluate distal neurovascular status with any lower leg injury to rule out acute compartment syndrome (1)[B].
Diagnostic Tests & Interpretation
  • X-rays: Initial studies are static films. 50% of syndesmotic injuries have avulsion fractures associated:
    • Weight-bearing anteroposterior view:
      • Tibiofibular clear space is among most sensitive indicators of syndesmotic injuries. Measured 1 cm proximal to ankle joint; widening demonstrated by >6 mm between medial border of fibula and medial cortical density of tibia.
      • Tibiofibular overlap; measured 1 cm proximal to joint; normal is >6 mm overlap between medial border of fibula and lateral border of tibia
      • Medial clear space should be <4 mm; >4 mm termed diastasis
    • Standing mortise view to evaluate talocrural angle; the angle of a line drawn across tips of malleoli intersecting with a line perpendicular to a line drawn across the superior aspect of tibial plafond. Variation from contralateral side of >5° is significant.
    • Lateral
  • Dynamic radiographs:
    • Cotton test: Grasp distal fibula and pull laterally; modified cotton test: Push or pull fibula in sagittal plane. Comparison to contralateral side is frequently required.
    • Varus and valgus ankle stress views are essential to assess instability.
    • External rotation stress views not considered reliable indicators of syndesmotic injury
  • P.571

  • MRI can clarify diagnosis and extent of soft tissue injury:
    • Compared with ankle arthroscopy, had sensitivity 100%/100% and specificity 93%/100% for anterior inferior/posterior inferior tibiofibular ligament disruption, respectively
  • CT helpful for bony detail of suspected talar dome injuries (2)[B].
Differential Diagnosis
  • Pronation-external rotation ankle fracture (Weber type C)
  • Supination-external rotation ankle fracture (Weber type B)
  • Fracture of the proximal fibula (Maisonneuve)
  • Ossification of the syndesmosis
  • Calcification of the syndesmosis
  • Deltoid ligament tear
  • Talar dome fracture
  • Tibiofibular synostosis resulting in prolonged pain and chronic disability
845.03 Tibiofibular (ligament) sprain, distal

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