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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