Ankle Fracture

An ankle fracture can involve the lateral malleolus, medial malleolus, posterior malleolus or combinations of these structures with associated deltoid and syndesmotic ligament injury.

The treatment question is not simply whether a malleolus is fractured. The key question is:

Is the talus stable and anatomically centred within the ankle mortise?

Loss of even small degrees of talar alignment substantially alters ankle contact mechanics.

Danis Weber classification

Classifies the fibular fracture according to its relationship to the distal tibiofibular syndesmosis.

Weber A

Fibular fracture below the syndesmosis.

Usually stable if the medial structures are intact.

Often corresponds to supination adduction injury.

Weber B

Fibular fracture at the level of the syndesmosis.

Syndesmotic stability varies.

Commonly corresponds to supination external rotation.

Weber C

Fibular fracture above the syndesmosis.

Strongly associated with syndesmotic disruption and an unstable ankle.

A very proximal Weber C fracture associated with syndesmotic and medial injury is a Maisonneuve fracture.

Palpate the entire fibula in every apparently isolated medial ankle injury.

Lauge Hansen classification

Describes foot position followed by direction of deforming force.

Supination external rotation

Most common pattern.

Stage 1:

Anterior inferior tibiofibular ligament injury.

Stage 2:

Oblique spiral distal fibular fracture at the syndesmosis.

Stage 3:

Posterior inferior tibiofibular ligament rupture or posterior malleolar fracture.

Stage 4:

Medial malleolar fracture or deltoid ligament rupture.

Supination adduction

Stage 1:

Distal fibular avulsion or transverse infrasyndesmotic fracture.

Stage 2:

Vertical medial malleolar fracture, often with medial plafond impaction.

Pronation external rotation

Stage 1:

Medial malleolar fracture or deltoid disruption.

Stage 2:

Anterior syndesmotic injury.

Stage 3:

Spiral fibular fracture above the syndesmosis.

Stage 4:

Posterior syndesmotic injury or posterior malleolar fracture.

Pronation abduction

Stage 1:

Medial malleolar fracture or deltoid disruption.

Stage 2:

Syndesmotic injury.

Stage 3:

Transverse or comminuted suprasyndesmotic fibular fracture.

The mechanism classification is useful for understanding injury sequence, but it does not predict every ligament injury reliably.

Patients present with ankle pain, swelling and inability or difficulty bearing weight.

Inspect for:

• Gross dislocation
• Open wound
• Skin tenting over the medial malleolus
• Fracture blisters
• Medial tenderness
• Proximal fibular tenderness

Document:

• Dorsalis pedis and posterior tibial pulse
• Superficial peroneal sensation
• Deep peroneal sensation
• Tibial nerve sensation
• Motor function where pain permits

An ankle fracture dislocation can rapidly threaten medial skin and requires immediate reduction.

Obtain:

• AP
• Mortise
• Lateral ankle radiographs

The mortise view is obtained with approximately 15° internal rotation and allows assessment of talar centring.

Obtain full length tibia and fibula imaging when:

• Proximal fibula is tender
• Medial injury exists without obvious distal fibular fracture
• Maisonneuve injury is possible

CT: obtain for:

• Posterior malleolar fracture
• Trimalleolar fracture
• Pilon overlap
• Complex articular injury
• Preoperative planning where posterior fragment morphology changes approach

Stable versus unstable isolated Weber B fractures can be clarified with weight bearing radiographs once pain allows or selected stress imaging.

Medial clear space widening suggests deep deltoid incompetence and talar instability, but interpretation should consider mortise positioning and comparison with the superior clear space.

Emergency reduction

Immediately reduce:

• Fracture dislocation
• Threatened skin
• Neurovascular compromise
• Severe talar displacement

Use adequate analgesia or procedural sedation.

After reduction:

• Repeat neurovascular examination
• Obtain post reduction radiographs
• Apply a well moulded splint

Do not leave the ankle in a redislocated position because the splint was inadequately moulded.

Stable fracture

Stable isolated lateral malleolar fractures with a congruent mortise can be managed nonoperatively using a walking boot or functional brace.

Early weight bearing as tolerated is increasingly appropriate in stable injuries.

Repeat imaging is required if stability was initially uncertain.

Unstable fracture

Operative fixation is appropriate for:

• Bimalleolar fracture
• Bimalleolar equivalent fracture with deltoid incompetence and talar shift
• Trimalleolar fracture with instability
• Talar displacement
• Unstable syndesmotic injury
• Displaced medial malleolar fracture causing mortise incongruity
• Open fracture
• Failure to maintain acceptable reduction

Lateral malleolus

Simple oblique fibular fractures can be treated with lag screw compression plus a neutralisation plate or with an antiglide construct.

Comminuted fibular fractures require restoration of:

• Length
• Rotation
• Alignment

A bridging plate can preserve comminution biology.

Fibular shortening is unacceptable because it permits lateral talar shift.

Medial malleolus

Reduce the articular surface anatomically.

Common fixation uses:

• Lag screws
• Screw plus antiglide strategy for vertical patterns
• Cerclage compression constructs for small fragments

A vertical medial malleolar fracture must be protected against vertical shear rather than treated as a simple transverse avulsion.

Posterior malleolus

The older rule of fixing only fragments involving more than 25% of the articular surface is no longer sufficient.

Fixation should be considered according to:

• Articular displacement
• Posterior fragment morphology
• Involvement of the incisura
• Syndesmotic instability
• Persistent posterior talar subluxation
• Size of the fragment

Direct posterior reduction is increasingly preferred for substantial displaced fragments because it restores both articular congruity and the posterior syndesmotic attachment.

Syndesmosis

After malleolar fixation, assess syndesmotic stability.

Fix an unstable syndesmosis only after the fibula has been restored to correct length and rotation.

Options include:

• 3.5 or 4.5 mm syndesmotic positioning screw
• Flexible suture button construct

A positioning screw should stabilise rather than compress the distal tibiofibular relationship. AO technique places the screw just above the distal tibiofibular joint, parallel to the plafond, with the ankle neutral.

Malreduction of the syndesmosis is a major cause of poor outcome.

Deltoid ligament

Routine deltoid repair is unnecessary when fixation restores a congruent stable mortise.

Explore or repair when:

• Medial tissue is interposed and blocks reduction
• Persistent medial instability remains despite correct osseous and syndesmotic reconstruction.

Postoperative management

Begin ankle movement once wound condition and fixation stability permit.

Stable anatomically reconstructed fractures can often begin early protected weight bearing, although severe fractures, poor bone quality and syndesmotic constructs may require greater restriction.

Major complications include:

• Wound problems
• Infection
• Syndesmotic malreduction
• Fibular shortening
• Ankle stiffness
• Post traumatic osteoarthritis
• Symptomatic hardware
• Nonunion, particularly medial malleolus
• Chronic instability