Definition
High ankle sprain
Epidemiology
Uncommon
- often unrecognised or misdiagnosed as lateral ligament injuries
- seen in ice hockey
1-15% of ankle sprains involve the syndesmosis
Mechanism Injury
Hyperdorsiflexion and forced external rotation
Anatomy
Structures
- anterior inferior tibiofibular ligament (AITFL)
- posterior inferior tibiofibular ligament (PITFL)
- interosseous ligament (provides only 10% of strength)
Examination
1. Tenderness over the AITFL
2. Positive squeeze test
- pain at ankle with squeezing the tibia & fibula at mid-calf
3. Painful ER
- probably most reliable test
- neutral ankle with knee flexed 90o
- hold tibia in neutral
- externally rotate foot
Xray
Usually is no evidence of syndesmotic widening
3 reliable indicators of syndesmotic widening
1. Clear space
- between the medial border of the fibula and the lateral border of the posterior tibia (incisura fibularis)
- measured 1 cm above the plafond
- distance should be approximately 5 mm or less on both the AP and mortise views in the normal ankle
2. Overlap of the fibula and the anterior tibial tubercle
- greater than 6 mm on the AP views
- greater than 1 mm on the mortise view
3. Stress films for syndesmotic instability
- application of an external rotation and abduction force
- anesthesia is often required because of the painful nature of this examination
Chronic
May see HO / MO interosseous ligament
CT
Normal
MRI
Highly accurate
- see disruption of ligament
- bone contusions posteromedial talus and posteromedial tibia
Arthroscopy
Inspect the syndesmosis under external rotation stress test
- see widening > 2mm between tibia and fibula
- can also visualise AITFL and PITFL
- often a tibial chondral injury
Management
1. Xray evidence of widening
Management
- diastasis screw / tightrope
2. Syndesmotic injury with no widening
Takes 6 - 12 weeks to resolve
- impossible to strap
- WBAT but no impact sports 6 weeks
3. Chronic injury / pain
Ogilvie-Harris Arthroscopy 1994
- arthroscopic debridement of sydesmosis and chondral injuries in 19 patients
- good results reported
- elimination of external rotation test