An approach to ankle x-rays
Aric Storck PGY2(acknowledgement to Dr. Dave Dyck for several slides)
September 11, 2003
Objectives
Review basic ankle fracture classification
Review x-rays of common ankle fractures
Discuss management of common ankle fractures
Case 1:
25 year old female• Jumped off roof
• Right ankle pain
• Inability to weight bear on right foot
What else do you want to know on history and physical examination?
Does she need x-rays ?
Ottawa Ankle Rules:
Order ankle x-rays if acute trauma to ankle and one or more of• Age 55 or older
• Inability to weight bear both immediately and in ER (4 steps)
• Bony tenderness over posterior distal 6 cm of lateral or medial malleoli
Sensitivity ~100% Specificity ~40%
You have decided to order an “ankle x-ray.” The nurse entering your orders asks which views you want …
Ankle X-rays: 3 views
AP• Identifies fractures of malleoli, distal tibia/fibula,
plafond, talar dome, body and lateral process of talus, calcaneous
Mortise• Ankle 15-25 degrees internal rotation
• Evaluate articular surface between talar dome and mortise
Lateral • Identifies fractures of anterior/posterior tibial margins,
talar neck, displacement of talus
AP x-ray:
Identifies fractures of • malleoli
• distal tibia/fibula
• plafond
• talar dome
• body and lateral process of talus
• calcaneous
Now apply what you’ve learned …
Lateral malleolar fracture
Tib/fib clear space <5mm
Tib/fib overlap >10 mm
No evidence of syndesmotic injury
Mortise X-Ray
Taken with ankle in 15-25 degrees of internal rotation
Useful in evaluation of articular surface between talar dome and mortise
Mortise x-ray:
Medial clear space• Between lateral border of
medial malleous and medial talus
• <4mm is normal
• >4mm suggests lateral shift of talus
Mortise x-ray:
Talar tilt • Normal = -1.5 to +1.5
degrees (ie. Parallel)
• Can go up to 5 degrees in stress views
• <2mm difference between medial and lateral talar/plafond distances
Lateral x-ray:
Identifies fractures of • Anterior/posterior tibial
margins
• Talus
• Displacement of talus
• Os trigonum
Stable vs Unstable
The ankle is a ring• Tibial plafond
• Medial malleolus
• Deltoid ligaments
• calcaneous
• Lateral collateral ligaments
• Lateral malleolus
• Syndesmosis Fracture of single part usually
stable Fracture > 1 part = unstable
Source: Rosen
Lauge-Hansen:
15 basic types of injury in 5 major categories• Described by two words
1.Position of foot at time of injury
2.Direction of talus within mortise causing fracture
• Eg: supination-external rotation
• Further subdivided into worsening areas of injury
Impossible to remember and clinically useless in the ED
Danis-Weber
• Defines injury based on level of fibular fracture• A=below tibiotalar joint
• No disruption of syndesmosis
• Usually stable
• B=at level of tibiotalar joint
• Partial disruption of syndesmosis
• C=above tibiotalar joint
• Disrupts syndesmosis to level of fracture
• unstable
• THE MORE PROXIMAL THE FIBULAR # THE MORE SEVERE THE INJURY
AO classification:
Similar to Danis-Weber scheme
Takes into account damage to other structures (usually medial malleolous)
~2 pages of classifications• Remember them all for your exam!
Pott’s classification:
Easy to remember
First degree• unimalleolar
Second degree• bimalleolar
Third degree• trimalleolar
Lateral Malleolar FractureDanis-Weber A
Mechanism• Suppination/adduction (inversion)
Mortise intact Stable fracture Treatment
• Below knee cast
Bimalleolar (lat & post malleoli)
Mechanism• Inversion
• Avulsion of posterior malleolus (post tibiofibular ligament)
Medial mortise wide• Suggests instability
Management• Posterior slab
• Orthopedic consult
Source: McRae’s Practical Fracture Treatment
Unstable• Multiple ligamentous injuries
• Usually involves syndesmosis
Treatment• Posterior slab
• Urgent orthopedic consultation
• ORIF
Trimalleolar Fractures
Fracture of distal tibial metaphysis• Often comminuted
• Often significant other injuries Mechanism
• Axial load
• Position of foot determines injury Treatment
• Unstable
• X-ray tib/fib & ankle
• Orthopedic consultation
Pilon (tibial plafond) fractures
Source:Rosen
Tillaux Fracture
Occurs in 12-14 year olds• 18 month period when epiphysis is closing
Salter-Harris 3 injury• Runs through anterolateral physis until reaches fused part,
then extends inferiorly through epiphysis into joint
• Visible if x-ray parallel to plane of fracture (may require oblique)
Mechanism• External rotation
• Strenth of tibiofibular ligament > unfused epiphysis
Tillaux Fracture
Management• Inadequate reduction of articular surface can lead
to early OA
• Gap >2mm in articular surface is unacceptable
• Advanced imaging techniques may be necessary
• Early orthopedic consultation
• Non-displaced• NWB below knee cast
• Displaced• surgery
Maisonneuve Fracture
Mechanism• Eversion + lateral rotation
• May cause medial malleolar fracture or deltoid ligament disruption
• Injury proceeds along syndesmosis and involves proximal fibula
Always rule out Maisonneuve fracture in medial malleolar/ligamentous injury
Maisonneuve Fracture
Mechanism• Eversion + lateral rotation
• Causes medial malleolar fracture or deltoid ligament disruption
If injury proceeds along syndesmosis it involves proximal fibula = Maisonneuve Fracture
Always rule out Maisonneuve fracture in medial malleolar/ligamentous injury
As talus continues to rotate• Posterior tib-fib ligament ruptures
• Interosseous membrane rips
• Gross diastasis
• Dupuytren fracture – dislocation of the ankle