AVN
Largely related to degree of displacement
Incidence
Hawkins Type I
- 0% to 13%
Hawkins Type II
- 20% to 50%
- usually only patchy and not a problem (rarely collapses)
- usually unites
Hawkins Type III / IV
- 90% to 100%
- often a problem
Hawkins Sign 1970
Means talus is vascularised
- makes diagnosis of AVN unlikely
AP view
- at 6 - 8 weeks see disuse atrophy of bones
- due to NWB
- thin rim of radiolucency under cartilage of talar dome
- subchondral atrophy
MRI
Best method to diagnose AVN
CT
NHx
Usually posterolateral corner
- furtherest from medial blood supply
Collapse occurrs despite years of NWB
- NWB does not prevent collapse
Creeping substitution can take up to 36 months
Collapse in most is well tolerated
Hawkins advocates weightbearing once united as re-ossification takes years
Management Limited collapse with OA
Arthrodesis of the affected joint
Management Complete collapse
Issue
- have a dead talus
- very difficult to obtain tibio-talar-calcaneal fusion
1. Blair fusion / tibio-talar arthrodesis / sliding anterior tibial graft
Advantage
- maintains length
Anterior approach between EDL and EHL
- excise avascular body
- use saw to take 5 x 2.5 cm graft anterior tibia
- slide graft from distal tibia
- insert into notch in residual viable talar neck and head
- foot in 0o DF, 5o valgus, 10o ER
- single screw x graft into tibia
- additional tibio-talar scrws
- Pack cancellous bone grafts around the fusion site.
- Apply a long leg cast with the knee flexed 30o
Results
- 4 united, 3 pseudos
- 5 good, 1 fair, 1 poor
2. Pantalar fusion with IM nail
3. Ilizarov Tibio-calcaneal Fusion
Disadvantage talus excision
- makes leg short
- 3cm short on average
Technique
- frame tibio-calcaneal fusion
- Ilizarov proximal corticotomy and lengthening
Mal-union
Incidence
More of a problem than AVN in Type II
- may be up to 40%
- most common with non operative or single incision operations
Issue
Varus secondary to medial comminution
- creates cavus foot with supination
- walk on lateral border of foot / walk with IR foot
- predispose to premature OA
Options
1. Talus osteotomy
2. Medial column lengthening with tri-cortical graft
3. Lateral column shortening
Arthritis
Subtalar joint arthritis
- most common complication
- rarely requires fusion
Non operative
STJ
- UCBL
Ankle
- moulded AFO
Operative
Fusion
Delayed Union
Definition
- > 6 months
- incidence is 10%
- very common
Non-union
Definition
- >12 months
- rare