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 branchesSEE 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 vascularityo T1 = looking at fat, bone with necrosis will lose marrow (fat) so it will look darko 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 WBo PTB casto Can take up to 24 months to revascularize o Compliance difficulto 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 conservativelyo 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 cartilageo Most effective for lesions less than 1.5 cm
