10 - Talus Fracture

Question 1

Anatomy

Answer 1

• Surface 60% cartilage
• No muscular insertions
• Blood supply in tenuous due to lack of soft tissue attachment
• Component of 3 joints (STJ, TN, ANKLE)

Question 2

Blood supply

Answer 2

• Artery of tarsal canal
• Artery of tarsal sinus
• Dorsal neck vessels
• Deltoid branches

SEE DIAGRAMS

Question 3

Artery of tarsal canal

Answer 3

• Supplies the MAJORITY of the talar body

Question 4

Fracture incidence

Answer 4

• 2 % of all fractures
• 6-8% of foot fractures
• High complication rates (Avascular necrosis, Post-traumatic arthritis)

Question 5

Mechanism of injury

Answer 5

• Hyper-dorsiflexion of the foot on the tibia
• Neck of talus impinges against anterior distal tibia, causing neck fracture
• If force continues, talar body dislocates posteromedial around deltoid ligament
• Previously called “aviator’s astragalus”
• Usually due to motor vehicle accident or falls from height

Question 6

Hawkins classification of talar neck fractures (1970)

Answer 6

• Of the many fracture classifications this one has value
• Excellent correlation with prognosis
• Predictive of AVN rate
• Widely accepted
• 53% Overall AVN incidence

Question 7

Hawkins I

Answer 7

• Non-displaced neck fracture
• Look at the cortex for alignment
• AVN 0 – 13 %

Question 8

Hawkins II

Answer 8

• Displaced neck fracture
• Subtalar subluxation
• AVN 20 – 50 %

Question 9

Hawkins III

Answer 9

• Subtalar and ankle joint dislocated
• Talar body is tethered around deltoid ligament
• AVN 83 – 100 %
• This makes sense because you are tearing
  the blood supply to the talus

Question 10

Hawkins IV

Answer 10

• Includes talonavicular subluxation
• Rare variant
• Complex talar neck fractures which do not fit classification can be included

Question 11

Goals of management

Answer 11

• Immediate reduction of dislocated joints to prevent joint and
  soft tissue damage
• Anatomic fracture reduction to restore function
• Stable fixation to promote healing and facilitate union
• Facilitate union
• Avoid AVN
• Provide a platform for early active rehabilitation (Move it or lose it)

Question 12

Avascular necrosis (AVN)

Answer 12

• Ischemia
• Due to arterial interruption
• Hallmarks on x-ray (increased density) = Sclerosis and Collapse****

Question 13

AVN imaging - plain radiographs

Answer 13

o Sclerosis

o Decreases with revascularization

Question 14

AVN imaging - MRI

Answer 14

o Very sensitive to decreased vascularity
o T1 = looking at fat, bone with necrosis will lose marrow (fat) so it will look dark
o The MRI often shows patchy areas of bone death

Question 15

AVN imaging - CAT scan

Answer 15

o Computed axial tomography
o Better 3D representation
o Confirms displaced vs non-displaced fractures

Question 16

AVN imaging - 3D reconstruction

Answer 16

o Can do this image with a CT scan
o Reconstructed CT scan into a 3D view
o Can see the extent of the dislocation very well

Question 17

AVN treatment - PRE-collapse

Answer 17

o	Modified WB
o	PTB cast
o	Can take up to 24 months to revascularize 
o	Compliance difficult
o	Efficacy unknown

Question 18

AVN treatment - POST-collapse

Answer 18

o Observation if asymptomatic

o Ankle fusion if symptomatic (Blair fusion if symptomatic)

Question 19

True answer on treatment

Answer 19

o There is no way to fix dead bone, except to let the body get rid of dead bone and make new bone by restoration of blood supply
o Revascularization process can take a long time – might have modified weight-bearing for up to 2 years

Question 20

Post-traumatic arthritis

Answer 20

• Most commonly involves STJ

- Treatment is arthrodesis

Question 21

Talar body fracture

Answer 21

• Treatment strategy and outcomes similar to talar neck fractures
• Medial or Lateral Malleoli Osteotomy frequently required

Question 22

Osteo-chondral defect (OCD)

Answer 22

• Not uncommon especially in chronic recurrent sprains and instability (Inverted ankle injury)
• Talus (Drive shoulder of talus up into tibia and knock off a piece of bone, or Intraarticular fracture)
• Tibia

Question 23

Berndt & Hardy Classification

Answer 23

CORRELATED TO OUTCOME (so actually useful)***

• I – Small area of compression
• II – Partially detached OCD
• III – Fully detached OCD but remains in crater
• IV – Displaced

Question 24

Notes

Answer 24

• I and II do better
• III and IV do worse

Maybe read on this a little more?

Question 25

Generalizations KNOW THIS

Answer 25

• Medial – Posterior – Deeper = More bone, less cartilage

- Lateral – Anterior – Shallower (thin and larger, more superficial) = Less bone, more cartilage

Question 26

Hawkins type I treatment

Answer 26

On-weight bearing cast for 4-6 weeks followed by removable brace and motion

Percutaneous screw fixation and early motion is also a viable option
o Improved muscle health, tendon health, bone health

Immobilization 
o	Bone gets weaker from demineralization – osteoporosis 
o	Fibrosis of the joint (stiffness) 
o	Atrophy of bone 
o	Devitalized cartilage 

Tendon
o Tendon does not even heal correctly when there is no stress or movement

Question 27

Hawkins type III treatment

Answer 27

• Stable fixation for early range of motion

Question 28

Hawkins sign

Answer 28

Subchondral lucency of the talar dome
- If this is present, no worry of AVN

Read up on this a little more

Question 29

MRI study example

Answer 29

• This is a posteromedial view

- Type III because it is completely detached but no displaced

Question 30

Acute or chronic

Answer 30

• Chronic because there is no fluid and ring of white if it is

Question 31

MOST effective treatment for talar dome OCD?

Answer 31

Depends on the lesion:
o I = usually conservatively
o II = usually conservatively
o III and IV = usually excise

Question 32

Excision and micro-fracture

Answer 32

o Removes the piece and break into the marrow space to release stem cells and bone healing growth factors
o Heals with fibro cartilage, not hyaline cartilage
o Most effective for lesions less than 1.5 cm