Talar Neck Fractures -

Anatomy

60% of the bone is covered by articular cartilage
Bone density is greater in the lateral part of the head than the medial part of the head, & in the inferolateral part of the body than the inferomedial
neck of the talus deviates around 20° medially in the adult
There are two bony processes, posterior & lateral, that can be fractured. The posterior process consists of a medial & lateral tubercle. The two are separated by a groove for FHL. An unfused lateral tubercle is called an os trigonum
talus has no muscular or tendinous attachments

This is by branches of the peroneal artery, posterior tibial artery & dorsalis pedis
perforating branch of the peroneal artery anastomoses with the dorsalis pedis artery to form the artery of the tarsal sinus. This anastomoses with the artery of the tarsal canal, a branch of the posterior tibial artery
deltoid branches arise from the posterior tibial artery, & supply the medial third of the talar body
Multiple branches to the neck arise from the dorsalis pedis artery, in addition to the anastomotic branch to the artery of the tarsal sinus
Branches of the peroneal artery make a minor contribution to the posterior process

Usually due to hyperextension of the forefoot with the hind foot in equinus – as in aviator’s astralagus or when pushing on brakes

best view to assess the position of the neck fracture is with the foot maximally plantar flexed, pronated 15°, & with the tube angled 75° cephalad from the horizontal (Canale)

By the Hawkins classification.

Type I
- nondisplaced vertical fracture of the talar neck
Type II
- displaced fracture of the talar neck with subluxation or dislocation of the subtalar joint (the ankle joint remains aligned). The head tends to displace into varus
Type III
- displaced fracture of the talar neck with dislocation of the body of the talus from both the ankle & subtalar joints
Type IV
- displaced fracture of the talar neck with dislocation of the head of the talus
- body tends to displace posteromedially, & tilt into plantarflexion

ORIF is usually required. On very rare occasions an anatomical reduction can be obtained & maintained by closed means
strongest biomechanical construct has been shown to be two screws passed in an antegrade fashion from the body into the head of the talus. The screws should ideally be titanium to allow MRIs
typical approach is with two incisions, one medial & one lateral, to verify the reduction on both sides of the neck

body usually rotates around the deep deltoid ligament fibres, to point laterally & cephalad. It is vital to retain the deep deltoid fibres, because these often provide the only remaining blood supply to the body of the talus. If the body cannot be reduced, it may be necessary to perform a medial malleolar osteotomy. A transverse calcaneal traction pin may be used as a reduction aid
Delayed primary closure should be considered because of the extreme swelling in the area

rate of infection is high in this injury. If infection becomes established in the body of the talus it is virtually impossible to eliminate, & treatment consists of talectomy & calcaneotibial fusion

Residual dorsal displacement of the head fragment limits ankle dorsiflexion & produces a painful gait
most frequent malunion is in varus. This leads to a varus hindfoot, ↑ weight bearing on the lateral side of the foot & stress on the subtalar joint

Type I – 0-13%
Type II – 20-50%
Type III – 83-100%
Overall rate is between 21 & 58%, making this the most common complication. AVN is apparent as an apparent ↑ density; actually the surrounding bone is becoming osteopenic because it is nonweightbearing
Hawkins’ sign may appear at the 6 to 8 week mark. It consists of a radiolucent line just below the subchondral surface on the AP of the ankle, & is a sign of viability which rules out AVN
MRI will clearly demonstrate AVN at three weeks
Union will still occur when AVN is present. The patient should be kept non weight bearing until union has occurred
It takes up to 3 years for full creeping substitution to occur
patient may be placed in a PTB once union has occurred, until the avascular body has reconstituted
In patients with collapse of the talus & degenerative joint disease, a tibiocalcaneal fusion can be performed, or a Blair fusion (this consists of excision of the talar body, & placement of a sliding corticocancellous graft from the anterior distal tibia into the residual viable talar head & neck). The Blair fusion preserves the appearance of the ankle

This is common, due to articular cartilage damage at the time of injury & the lack of motion necessary to allow the talar neck fracture to unite