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British Medical Books Health Issues Computerized Tomography

Ankle Fractures

  • common fracture
  • tendency for operative Rx in more severely injured ankles

Anatomical & Biomechanical considerations

  • articulations of 3 bones: distal tibia, distal fibula & talus
  • major articulation between dome of the talus & tibial plafond - forms a congruent saddle shaped joint
  • talus has a medial facet (articulates with medial malleolus) & a lateral facet (articulates with lateral malleolus)
  • 80 to 90% of the load is transmitted thro the plafond to the dome of the talus
    • with varus or valgus stress 20% transmitted thro the medial facet & 10% thro the lateral facet
    • normally the 17% of the load is transmitted proximally thro the fibula

Ligaments

  • the distal tib & fib are bound by the anterior & posterior tibio-fibular ligs & the syndesmosis
  • laterally the fibula is attached to the hindfoot by 3 ligs:
    • anterior talo-fibular lig
    • calcaneofibular lig
    • posterior talo-fibular lig
  • medially the ankle is stabilized by the deltoid lig which has 2 parts:
    • superficial part - fans onto the neck of the talus - resists eversion &
    • deep part - inserts onto the medial part of the talus - resists external rotation of the talus
  • plantar flexion is a combination of sliding & rolling
  • ROM with axial loading is 30° of dorsiflexion & 45° of plantar flexion
  • motion of the talus in dorsi & plantar flexion causes motion of the fibula
  • new studies show that the primary stabilizer of the ankle is on the MEDIAL side of the joint & that the major instability is EXTERNAL ROTATION of the talus, not lateral shift (which is a two dimensional X Ray illusion)
  • during peak loading the ankle joint carries 4X’s the body weight

Goals of Treatment

  • most scientific studies do not show that operative Rx gives better clinical results

2 indications for surgery

  • static incongruity = step off in the weight bearing part of the articular surface (pilon fracture’s)
  • dynamic incongruity or instability = abnormal talar tracking
    • operative Rx results in an anatomical reduction more frequently
    • incidence of infection with ORIF - 1 to 4%

Classification

  • 2 purposes of a classification
    • determine the most appropriate treatment
    • prognosticate
  • 2 widely used classifications

Lauge-Hansen

  • based on fracture patterns in cadavers
  • 2 part nomenclature
    • the 1st word = the position of the foot at the time of injury: supination or pronation
    • the 2nd word = direction of deforming force: rotation (ER or IR) or translation (abd or add)
  • Concept:
    • supination puts the lateral structures under tension
    • pronation puts the medial structures under tension
  • Supination ER fracture
    • Injury begins anteriorly & progresses around the ankle - stage 1 to 4
      • 1 = injury to anterior tib-fib lig
      • 2 = lateral malleolus
      • 3 = posterior capsule or posterior malleolus
      • 4 = medial malleolus or deltoid lig
  • Pronation ER fracture
    • injury begins medially & ends posteriorly (also 1 to 4)
  • Supination abduction fracture
    • initial injury is to the lateral malleolus followed by a medial fracture or lig injury
  • Pronation abduction fracture
    • initial injury is 1st medial then lateral
  • complicated & difficult to apply
  • was designed as a guide for the Rx of closed unstable fractures

Weber Classification

3 Types

  • A, B & C
  • further subdivided into types 1, 2 & 3
  • popular system because it is easy to apply
  • type B fractures account for 80-90% of all ankle fractures

Diagnosis

History, mechanism of injury

  • twisting force

Clinical

  • open or closed
  • ST damage
  • localize tenderness

X-Rays

  • AP, lateral & mortise view (= true AP of the ankle joint)

1. isolated fractures of the lateral malleolus

  • 85% of these fracture have NO injury to the medial side
  • 1mm lateral shift of the talus decreases the contact area of the tib-talar joint by 42% (Ramsey & Hamilton)
  • recent studies - displacement of the fibula does not cause talar shift in isolated lateral malleolus fracture
  • operative Rx DOES NOT give better clinical results than conservative Rx
  • no dynamic instability without a medial injury - operative Rx not justified

2. combined medial & lateral injuries = bimalleolar fractures

  • fracture of the lateral malleolus + a medial malleolus or deltoid injury
  • an anatomic reduction yields better results

Diagnosis of a medial injury

  • medial tenderness
  • 5mm space between medial malleolus & talus (either on initial X ray or stress views)
  • deltoid ligament injuries should be considered to be bimalleolar fracture’s

ORIF of lateral malleolus

  • routine exploration of the medial side is not indicated unless there is block to reduction
  • delay in operative Rx is associated with
    • a higher rate of complications
    • difficulty in obtaining an anatomic reduction
  • Gustillo & Anderson grade I, II & IIIa - immediate ORIF with delayed closure at day 5
  • Gustillo & Anderson grade IIIb & c - debridement & external fixation

3. Injuries to the syndesmosis

  • injuries proximal to the plafond - injury to the syndesmosis

Diagnosis of a syndesmosis injury

  • 5mm between the distal aspects of the tib & fib on the mortise view
  • persistent displacement of the fibula will result in a poor clinical outcome

Syndesmosis screw (4,5mm cortical screw thro 3 or 4 cortices) is required

  • a lag screw should not be used - narrowing of the syndesmosis with dorsiflexion
  • screw should be parallel to the joint line to avoid displacement of the fibula
  • screw is placed with the foot in dorsiflexion
  • screw is usually removed before weight bearing - can be left in

4. posterior malleolus fractures

  • clinical results of trimalleolar fractures are worse than bimalleolar fractures
    • fractures of > 30% of the posterior malleolus are associated with instability
  • reduction & fixation of the lateral malleolus usually reduces the posterior malleolus & restores stability
  • closed reduction of fractures < 25% have good clinical results
  • the posterior fragment can be approached thro a posterolateral incision

Post operative management

  • no substantial difference in: ROM or level of activity in patients Rx’ed with early mobilization & those Rx'ed with immobilization for 3 to 6 weeks
  • non union is uncommon in fracture's about the ankle
  • good result is expected in > 85% of cases of bimalleolar fracture’s if an anatomic reduction is achieved
  • poorer results occur with non anatomic reductions
  • patients can expect a gradual improvement in function as late as 9 years post-op
  • OA, when it occurs, develops within 2 years
    • uni-malleolar fractures < 5% incidence of OA
  • swelling is a usual finding after a fracture
    • more persistent & severe after ORIF
    • takes about 3 months to disappear after closed Rx & 9 - 18/12 after ORIF
  • removal of hardware
    • neither improves function nor reduces the incidence of complications
    • may give local pain relief