Definition
Fracture talus through articular cartilage into subchondral bone
- 2° force transmitted from distal tibia
Osteochondritis dissecans v osteochondral fracture
Epidemiology
6% ankle sprains
Average age = 25
M > F
Location
1. Anterolateral 50%
2. Posteromedial 50%
Aetiology
30% associated with other injuries
- medial and lateral malleolar fractures
- ankle sprains
A. Traumatic / anterolateral
2° to inversion injuries
- will usually heal
B. Atraumatic / posteromedial
2/3 caused by trauma
- 1/3 no history trauma
- are chronic and won't heal
Non-traumatic causes
- ? AVN
- 20% bilateral (can be asymptomatic)
- some patients have multiple joints with OCD
- can have family history of talus OCD
Pathology
Start as acute intra-articular fracture
Bony fragment may
- revascularise & unite
- undergo AVN & not unite
Overlying cartilage may degenerate
Cyst may develop under fragment
Berndt & Harty Xray Classification
Stage 1
- subchondral compression fracture
Stage 2
- partially attached osteochondral fragment / flap
Stage 3
- fragment detached in-situ / not displaced
Stage 4
- detached displaced fragment
MRI
Determine stability of fragment
- stable lesion has intact overlying cartilage
- unstable lesion has fluid at fragment-crater interface
Stage 1
- stable
- no detachment, no synovial fluid
Stage 2
- partially detached, some synovial fluid
Stage 3
- completely detached, not displaced
Stage 4
- displaced
History
Lateral ankle sprain from inversion injury
Chronic symptoms after ankle sprain settled
- activity-related pain, stiffness & swelling
- crepitus, instability & locking (true locking rare)
Symptoms of lateral ligament instability
Examination
Tenderness around ankle joint
Pain with dorsiflexion / eversion
Decreased ROM, especially dorsiflexion
Effusion
Test for ligament instability
DDx
Chronic ligament instability
Lateral gutter ST impingement
Calcaneal fracture
Lateral process fracture
Tarsal coalition
Sinus tarsi syndrome
Management
Non Operative
Higher success with acute injury
- POP & NWB 6/52
- progressive to weight bearing over 3 - 4 months
Tol et al Foot Ankle Int 2000
- meta-analysis
- 14 studies with 201 patients
- 45% success rate
Operative
1. Percutaneous Drilling
Indication
- Type 1, 2
2. ORIF
Indications
- acute
- large type 2 , 3
- in situ but unstable and not healing
Approach
A. Lateral lesion
- approached through anterolateral approach
- ± Fibular osteotomy if large
B. Medial lesion
- approached through anteromedial approach
- ± medial malleolar osteotomy
Technique
- partially displace
- debride base
- insert bone graft as paste
- fix with bioabsorbably headless compression screws
3. Excision / curettage / abrasion / microfracture
Indications
- small lesion
- fragment detached with chondral lesion
Results
Tol Meta-analysis
- 88% success stage 3 and higher
- less if no curettage or dilling
- can do so arthroscopically
4. Allograft
Indications
- large lesions
- > 1cm diameter and > 5mm thick
Post operative
- PTB brace 1 year
Results
Gross Foot Ankle Int 2001
- 3/9 resorbed
4. Osteochondral autograft / mosaicoplasty
Indications
- stage 4 lesion
Donor Site
- taken from knee NWB surface
- allograft
Technique
- fresh frozen talus
- 6.5 mm chisel used to take 10 mm plug
- medial malleolar osteotomy
- 6.5 mm drill into OCD site with drill guide, over drill 4 mm
- dilator
- insert plug, countersink 1 - 2 mm
Results
Management Algorithm
Stage 1
Restricted activity / watch to see if heals
Stage 2
Symptomatic
- SL POP for 6/52
- Successful in 90%
Failure
1. ORIF
2. Removal of necrotic fragment & drill base
Stage 3
Surgery probably indicated as very unstable
- ORIF
Stage 4
Surgery
- acute ORIF if possible (i.e fragment is replaceable)
- chronic may have to discard fragment
- manage chondral defect / abrasion