10 - Talus Fracture Flashcards
Anatomy
- Surface 60% cartilage
- No muscular insertions
- Blood supply in tenuous due to lack of soft tissue attachment
- Component of 3 joints (STJ, TN, ANKLE)
Blood supply
- Artery of tarsal canal
- Artery of tarsal sinus
- Dorsal neck vessels
- Deltoid branches
SEE DIAGRAMS
Artery of tarsal canal
- Supplies the MAJORITY of the talar body
Fracture incidence
- 2 % of all fractures
- 6-8% of foot fractures
- High complication rates (Avascular necrosis, Post-traumatic arthritis)
Mechanism of injury
- 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
Hawkins classification of talar neck fractures (1970)
- Of the many fracture classifications this one has value
- Excellent correlation with prognosis
- Predictive of AVN rate
- Widely accepted
- 53% Overall AVN incidence
Hawkins I
- Non-displaced neck fracture
- Look at the cortex for alignment
- AVN 0 – 13 %
Hawkins II
- Displaced neck fracture
- Subtalar subluxation
- AVN 20 – 50 %
Hawkins III
- 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
Hawkins IV
- Includes talonavicular subluxation
- Rare variant
- Complex talar neck fractures which do not fit classification can be included
Goals of management
- 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)
Avascular necrosis (AVN)
- Ischemia
- Due to arterial interruption
- Hallmarks on x-ray (increased density) = Sclerosis and Collapse****
AVN imaging - plain radiographs
o Sclerosis
o Decreases with revascularization
AVN imaging - MRI
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
AVN imaging - CAT scan
o Computed axial tomography
o Better 3D representation
o Confirms displaced vs non-displaced fractures
AVN imaging - 3D reconstruction
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
AVN treatment - PRE-collapse
o Modified WB o PTB cast o Can take up to 24 months to revascularize o Compliance difficult o Efficacy unknown
AVN treatment - POST-collapse
o Observation if asymptomatic
o Ankle fusion if symptomatic (Blair fusion if symptomatic)
True answer on treatment
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
Post-traumatic arthritis
- Most commonly involves STJ
- Treatment is arthrodesis
Talar body fracture
- Treatment strategy and outcomes similar to talar neck fractures
- Medial or Lateral Malleoli Osteotomy frequently required
Osteo-chondral defect (OCD)
- 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
Berndt & Hardy Classification
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
Notes
- I and II do better
- III and IV do worse
Maybe read on this a little more?
Generalizations KNOW THIS
- Medial – Posterior – Deeper = More bone, less cartilage
- Lateral – Anterior – Shallower (thin and larger, more superficial) = Less bone, more cartilage
Hawkins type I treatment
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
Hawkins type III treatment
- Stable fixation for early range of motion
Hawkins sign
Subchondral lucency of the talar dome
- If this is present, no worry of AVN
Read up on this a little more
MRI study example
- This is a posteromedial view
- Type III because it is completely detached but no displaced
Acute or chronic
- Chronic because there is no fluid and ring of white if it is
MOST effective treatment for talar dome OCD?
Depends on the lesion:
o I = usually conservatively
o II = usually conservatively
o III and IV = usually excise
Excision and micro-fracture
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
