Epidemiology
Second most common hindfoot after calcaneal fractures
Aetiology
Aviators Astragalus
Fall from height
- hyper-dorsiflexion injury
- neck of talus strikes the anterior tibia
Anatomy
More than half surface covered by articular cartilage
- medial articular wall straight
- lateral articular wall curves posteriorly
- meet at posterior tubercle
Neck of talus
- medially 10 - 44o from axis of body
- plantar 5 - 50o
No muscle or tendon attachments
Ligaments
- deep deltoid medially
- ATFL, PTFL
- FHL tendon in groove posteriorly
- head supported by spring ligament (CN ligament)
Facets
- posterior / middle / anterior
- correspond to calcaneal facets
- sinus tarsi between posterior and middle
Blood Supply
3/5 talus covered by articular cartilage
- blood can only enter through 2/5
1. Posterior tibial / artery of tarsal canal
- main supply to body
- branches to deltoid ligament
- enters talar neck and supplies most of body
2. Anterior tibial / Dorsalis pedis
- supplies head and neck
3. Peroneal / artery of tarsal sinus
- supplies head and neck head and neck
Pathology
Often with rotation
- with DF body of talus locks in mortice
- fracture neck on tibia
- remainder of foot displaces medially thru STJ
- disrupt inter-osseous and lateral / posterior ligaments
- dislocation of STJ and AKJ
Body of talus is forced out postero-medially swinging on intact deltoid
- comes to lie posterior to medial malleolus & anterior to T achilles
- often associated medial +/- lateral malleolus fracture
Classification Hawkins 1970
1. Undisplaced fracture
Fracture of neck between posterior and medial facet
- precluded by any displacement of 1 - 2 mm
- may need CT to confirm
- means only one blood supply is disrupted
AVN 10%
2. Subluxation / dislocation STJ
Subluxed posteriorly or medially
- blood supply through neck and in canal disrupted
- blood supply through medial body usually maintained
AVN 39% Vallier et al JBJS Am 2004
3. Subluxed STJ & AKJ
Body extruded postero-medially
- head maintains relationship with navicular
- 25 % open
- all three blood supplies are disrupted
AVN 67% Vallier et al JBJS Am 2004
4. Type 3 + subluxed TNJ
Dislocation of head and neck
- poor outcome
- significance is that blood supply to head may also be disrupted
AVN 90 - 100%
Examination
Open wounds
Skin under threat (Type III / IV)
NV compromise
- fragment can compress circulation
X-ray
Canale view
- evaluates talar neck
- foot 15o pronated
- beam angled 75o to foot
- look for medial shortening / varus
CT
Management
Non-operative
Indication
Only for true type 1 injuries
Technique
Frequent review to prevent loss of position
SL NWB POP 6/52
Operative Management
Goal
Anatomic reduction
- rotation / length / angulation of talar neck
Any displacement of 2mm
- increases contact stresses of STJ
- leads to premature STJ OA
Closed Reduction
Occasionally need to do closed reduction
- pressure on skin
- vascular compromise
- patient severely injury
Technique
- flex knee to relax gastrocnemius
- traction on plantarflexed foot to realign head and body
- varus / valgus correct as required
- place temporary percutaneous K wires
Timing of Surgery
Does early reduction prevent AVN?
Vallier et al JBJS Am 2004
- 102 patients
- no evidence that surgical delay increased AVN
- AVN associated with neck comminution and open fractures
- recommend is reasonable to wait for swelling to subside
Sanders 2004 JBJS Am
- similar conclusion
- 29 patients
- delay in surgery did not affect union or AVN rates
Surgical Technique
1. Closed Type 2 - 4
Position
- supine on radiolucent table
- tourniquet, IV Abx, II available
Incisions
- 2 incision technique
Anteromedial
- just medial to T anterior tendon
- begin at TNJ
- can extend to MM
- no stripping of dorsal neck
- preserve deep deltoid for blood supply
- may require medial malleolar osteotomy
- in this case can curve incision up and around medial malleolus
Anterolateral
- allows assessment of reduction
- lateral screw prevents compression into varus and loss of medial length
- lateral to EDL, mobilise EDB
- > 7 cm skin bridge
- expose lateral talar neck
Reduce and ORIF
- only accept anatomical reduction
- avoid varus and shortening medial neck
- anteromedial and anterolateral K wires
- insert proximal to articular surface of head
- aim into posterior body
- parallel
- check II
- cannulated lag screws (titanium for future MRI)
- minifragment screws for osteochondral fragments
2. Devitalised Type 3 / 4 with compound wound
Managment is controversial
1. Reasonable to clean / replace / ORIF
- if become's infected remove
- Abx spacer
- apply frame
- fuse late once infection cleared +/- lengthening
2. Can discard primarily & close wound
- fusion once soft tissues healed
- acute shortening and fusion with frame with proximal corticotomy and lengthening