David Sanders MD, MSc, FRCSC

London Health Sciences CentreUniversity of Western Ontario London, Ontario, Canada

Fractures of the Talus and Subtalar Dislocations

Outline:

Talar Neck Fractures• Anatomy• Incidence• Imaging• Classification• Management• Complications

Talar body, head and process fractures

Subtalar dislocations• Classification• Management • Outcomes

• Surface 60% cartilage• No muscular insertions

Anatomy

Blood SupplyArterial supply:• Artery of tarsal canal• Artery of tarsal sinus• Dorsal neck vessels• Deltoid branches

mediallateral

Inferior view of talus, showing vascular anastomosis

Vascularity• Artery of tarsal canal supplies majority of

talar body

Side ViewTop ViewDeltoid Branches

Posterior tuberclevessels

Artery of TarsalSinus

Artery ofTarsal Canal

Superior Neck Vessels

Superior Neck Vessels

Artery of TarsalSinus

Artery ofTarsal Canal

Posterior tuberclevessels

Incidence

• 2 % of all fractures• 6-8% of foot fractures• Importance due to high

complication rates• avascular necrosis• post-traumatic arthritis• malunion

Mechanism of Injury

• Hyperdorsiflexion of the foot on the leg

• Neck of talus impinges against anterior distal tibia, causing neck fracture

• If force continues:• talar body dislocates posteromedial• often around deltoid ligament

Injury mechanism

• Previously called “aviator’s astragalus”

• Usually due to motor vehicle accident or falls from height

• Approximately 50 % have multiple traumatic injuries

Biomechanics

• Theoretical shear force across talar neck:• 1200 N during active motion

[Swanson 1992]

Imaging• Complex 3-D structure• Multiple plain film

orientations:

Canale View

Canale View

• Ankle plantarflexion• 15 degree pronation• Tube 15 degree off vertical

Canale View

CT scan

• Can be a useful assessment tool

• Confirms truly undisplaced fractures

• Demonstrates subtalar comminution, osteochondral fractures

MRI Scan

• Primary role in talus injuries is to assess complications, especially avascular necrosis

• May be poor quality if extensive hardware present

Zone of osteonecrosis following distribution of Artery of Tarsal Canal

Talar Neck Fractures: Classification

• Hawkins 1970

• Predictive of AVN rate

• Widely used

Hawkins 1

• I: undisplaced

• AVN 0 – 13 %

Hawkins 2

• Displaced fracture• Subtalar subluxation

• A) fracture line enters subtalar joint

• B) subtalar joint intact

• AVN 20 – 50 %

Hawkins 3

• Subtalar and ankle joint dislocated

• Talar body extrudes around deltoid ligament

• AVN 83 – 100 %

Hawkins 4

• Incorporates talonavicular subluxation

• Rare variant• Complex talar neck

fractures which do not fit classification can be included

Classification:

• Comminution:• An important additional predictor of results,

especially regarding:• Malunion• Subtalar joint arthritis

Goals of Management

• Immediate reduction of dislocated joints• Anatomic fracture reduction• Stable fixation• Facilitate union• Avoid complications

Treatment of talar neck fractures

• Emergent reduction of dislocated joints• Stable internal fixation • Choice of fixation and approach depends

upon personality of fracture

Treatment of talar neck fractures

• Post operative rehabilitation:• Sample protocol:

• Initial immobilization, 2-6 weeks depending upon soft tissue injury and patient factors, to prevent contractures and facilitate healing

• Non weight-bearing, Range of Motion therapy until 3 months or fracture union

Hawkins I Fracture

Options:• Non-Weight-Bearing Cast

for 4-6 weeks followed by removable brace and motion

• Percutaneous screw fixation and early motion

Hawkins II, III, and IV fractures:

• Results dependent upon development of complications

• Osteonecrosis• Malunion• Arthritis

Case Example

• 29 yo male• ATV rollover• Isolated injury

LLE

Diagnosis

• Hawkins’ 3 talar neck fracture• Associated comminution, probably

involving medial column and subtalar joint

Controversies for this Case:

• Surgical timing• Closed reduction• Surgical approach• Fixation

Surgical timing

• Emergent reduction of dislocated joints

• Allow life threatening injuries to take priority and resuscitate adequately first

Closed reduction?

• May be very useful, particularly if other life threatening injuries preclude definitive surgery

• Difficult in Hawkins’ 3 and 4 injuries

Closed reduction technique:

• Adequate sedation• Flex knee to relax gastrocs• Traction on plantar flexed forefoot to

realign head with body• Varus/valgus correction as necessary

Closed reduction example

External Fixation

• Limited roles:• Multiply injured patient with

talar neck fracture in whom definitive surgery will be delayed

• Temporizing measure to stabilize reduced joints

Surgical Approaches: Options

• 1 incision techniques:• Anteromedial or• Anterolateral

• Problem: difficult to visualize talar neck and subtalar joint without significant soft tissue stripping

• Benefit: potentially less skin injury

Surgical Approaches: Options

• 2 incision technique:• Anteromedial and direct lateral

• Problem: 2 skin incisions, close together• Benefit: excellent fracture visualization at critical sites

of reduction and subtalar joint

1st Approach: Anteromedial

• Medial to TA and Anterior Compartment contents

• Make incision more posterior for talar body fractures to facilitate medial malleolar osteotomy

1st Approach: Anteromedial

• Provides view of neck alignment and medial comminution

2nd Approach: Direct Lateral

• Tip of Fibula directly anterior• Mobilize EDB as sleeve• Protect sinus tarsi contents

2nd Approach: Direct Lateral

• Visualizes Anterolateral alignment and subtalar joint

• Facilitates Placement of “Shoulder Screw”

Protect the skin post op

Fixation Options

• Stable Fixation to allow early motion is the goal

• 1200 N stress across talar neck during early motion

• (Swanson JBJS 1992)

Surgical Tactics: Fixation

• Anterior• Partial threaded screws• Fully threaded screws• Mini-fragment plates

• Posterior• Lag screws

Implant selection depends upon injury, degree of comminution, bone quality

But should be strong enough to withstand motion

Posterior to Anterior Fixation:• stronger than anterior to posterior fixation

with 2 screws• Able to withstand the theoretical shear force

of active motion (Swanson, JBJS 1992)

• Screws perpendicular to fracture site

90°

Anterior Screw Fixation:

Non-comminuted fractures:• Easy to insert under direct

visualization and no cartilage damage • Displaced type 2: 3 A-P screws

including medial “buttress” fully threaded cortical screws and lateral “shoulder” screws

Anterior Screw Fixation:

Comminuted fractures:• Buttress screw: comminuted

column; compression screws through non-comminuted column

• Mini-fragment screws for osteochondral fragments

• Consider Titanium for MRI

Anterior Plate Fixation:

• Comminuted fractures:• Medial and / or lateral mini-

fragment plates

Complications

• AVN• Malunion

• Nonunion• Arthritis

AVN: incidence after talus fracture

• Canale (1972): • I: 15 %• II: 50 %• III: 85 %• IV: 100 %

• Behrens (1988):• Overall 25 %

• Ebraheim/Stephen(2001):• Overall 20 %

AVN: Diagnosis

• Hawkins’ Sign: Xray finding 6-8 weeks post injury

• Presence of subchondral lucency implies revascularization

AVN: Imaging

• Plain radiographs: sclerosis common, decreases with revascularization

• MRI: very sensitive to decreased vascularity

AVN Treatment:

• Precollapse:• Modified WB• PTB cast• Compliance difficult• Efficacy unknown

• Postcollapse:• Observation• Blair fusion if

symptomatic

Malunion: Incidence

• Common: up to 40 %

• Most often Varus

Malunion: Diagnosis

• Varus alignment on clinical exam

• Dorsal malunion on Xray

Malunion

• Mechanical effects known• > 3 degrees: decreased ROM

(Daniels TR, JBJS 1996)• > 2mm: altered subtalar

contact forces (Sangeorzan J Orthop Res 1992)

Clinical Effect of Malunion

• Malunion:• More pain• Less satisfaction• Less ankle motion• Worse functional outcome

Malunion Rx:

• Calcaneus osteotomy• Tendo Achilles Lengthening

Post Traumatic Arthritis

• Incidence of post-traumatic arthritis• 30-90 %

Post-Traumatic Arthritis

• Most commonly involves Subtalar joint

• Rx: Arthrodesis

Nonunion

• Uncommon, even with AVN

• Delayed Union very common

• Frequently results in late malalignment

Talar Body Fractures

• Treatment strategy similar to talar neck fractures

• Medial or Lateral Malleolar Osteotomy frequently required

Medial Malleolar Osteotomy

Talar Body + Fibula Fracture

• Visualize body through the fibula fracture

Talar Body Case Example

• 58 year old female• 4 week old fracture• Missed initially

Case cont’d

• Extensive comminution into subtalar joint• Fragments very small

Selected Rx: Primary Arthrodesis

Osteochondral injuries

• Frequently encountered with talus neck and body fractures

• Require small implants for fixation• Excise if unstable and too small to fix

Osteochondral injuries

Osteochondral fragment repair

Large fragment repaired, small fragment excised

Talar Head and process fractures

• Treat according to injury• Operate when associated with joint

subluxation, incongruity, impingement or marked displacement

• Fragments often too small to fix and require excision

Case example: Talar head fracture

• Talar head injury• Subtle on plain xray

Talar Head fracture continued

• CT demonstrates subtalar injury and subluxation

Treatment of talar head fracture

• Required 2 incisions to debride subtalar joint from lateral approach, and reduce / stabilize fracture from medial side

Lateral process example• Usually require CT scan• Often excised due to size of fragments • Difficult to achieve union

Subtalar Dislocations

• Spectrum of injuries

Relatively Innocent

Very Disabling

Classification

• Usually based upon direction of dislocation:

• Medial dislocation: 85 %, low energy

• Lateral dislocation: 15 %, high energy

Other important considerations:

• Open vs Closed

• High or low energy mechanism

• Stable or unstable post reduction

• Reducible by closed means or requiring open reduction

• Associated impaction injuries

All have prognostic significance:

Important Distinction:

• Total talar dislocation, peri talar dislocation, or pan talar dislocation

• Results from continuation of force causing subtalar dislocation

• High risk of AVN, usually open, poor prognosis

Open peritalar dislocation with skin loss showing Imperfect reduction: Result was AVN and

pantalar fusion

Management of subtalar dislocation

• Urgent Closed reduction:• Adequate sedation• Knee flexion• Longitudinal foot traction• Accentuate, then reverse deformity

• Succesful in up to 90 % of patients

Open reduction:

• More likely after high energy injury

• More likely with lateral dislocation

• Cause:• soft tissue interposition

(Tib post, FHL, extensor tendons, capsule)

• bony impaction between the talus and navicular

Rehabilitation:

• Stable injuries: • 4 weeks immobilization• Physio for mobilization

• Unstable injuries:• Usually don’t require internal fixation once reduction

achieved

Outcome of Subtalar dislocations:

• Less benign than previously thought

• Subtalar arthritis:• Up to 89 % radiographically• Symptomatic in up to 63 %

• Ankle and midfoot arthritis less common

Summary:

Talar Neck Fractures• Anatomy• Incidence• Imaging• Classification• Management• Complications

Talar body, head and process fractures

Subtalar dislocations• Classification• Management • Outcomes

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