Ankle Imaging

Question 1

Ankle exposure factors and rationale

Answer 1

55 kVp - high image contrast, large attentuation difference
100 mA - fine focus image detail
0.05 s - gives required mAs of 5 when using 100mA, appropriate image density
No grid - minimal scatter radiation

Question 2

Imaging techniques for ankle

Answer 2

**AP (Mortise) **
- legs extended
- internally rotate 5 degrees to open up joint space
- centre midway between medial and lateral malleolus
- straight tube
- collimate lower third of tibia and fibula, ankle joint, lateral and medial malleoli, talus and surrounding soft tissues

**Lateral **
- ensure medial aspect of foot is in contact with IR
- roll on affected side
- malleoli should be superimposed vertically
- centre over medial malleolus
- foot to be as dorsiflexed as possible
- small foam wedge if needed

Oblique
- not common but if used then internally rotate 30 degrees using radiolucent pad
- angle 15-20 degrees cranially
- centre midway between malleoli

Question 3

Avulsion Fracture Distal Fibula

Answer 3

caused by inversion injury, tendon is stretched and pulls a fragment of bone off the distal fibula

Question 4

What projections for Avulsion Fracture Distal Fibula? Explain rationale for each

Answer 4

AP (Mortise) - to see the bone fragment that has been pulled off the fibula and the anatomy of ankle

Lateral - to see if there has been any anterior or posterior displacement of the fragment and to ensure all joints are in alignment

Question 5

Radiographic appearance of avulsion fracture distal fibula

Answer 5

a fragment of bone has been pulled off the corner of the distal fibula

Question 6

Trimalleolar Fracture

Answer 6

where all malleoli have been fractured

Question 7

What projections for Trimalleolar Fracture? Explain rationale for each

Answer 7

AP (Mortise) - shows fracture to the medial and lateral malleolus
Horizontal beam lateral - very serious fracture and will be unlikely to move, to see if there has been any anterior/posterior displacement, to see the posterior malleolus

Question 9

Radiographic appearance of trimalleolar fracture

Answer 9

fractures to all malleoli

Question 10

Potts’ Fracture

Answer 10

fracture of the lateral and medial malleoli, bimalleolar fracture

Question 11

What projections for Potts’ Fracture? Explain rationale for each

Answer 11

AP (Mortise) - shows fracture to the medial and lateral malleolus
Horizontal beam lateral - very serious fracture and will be unlikely to move, to see if there has been any anterior/posterior displacement

Question 12

Radiographic appearance of Potts’ Fracture

Answer 12

clear fracture lines in the lateral and medial malleoli

Question 13

Maisonneuve Fracture

Answer 13

fracture through proximal fibula and fracture in the medial malleolus

Question 14

What projections for Maisonneuve Fracture? Explain rationale for each

Answer 14

**AP (Mortise) **- to see the gap between medial malleolus and talus, fracture lines in the fibula and malleolus

Lateral - to see anterior/posterior displacement of the fragment

Question 15

Radiographic appearance of Maisonneuve Fracture

Answer 15

• increased gap between medial malleolus and talus
• fracture through proximal fibula and medial malleolus

Question 16

Pilon Fracture

Answer 16

when the talus puts upward pressure on the tibia caused a fracture in tibia and/or fibula

Question 17

What projections for Pilon Fracture? Explain rationale for each

Answer 17

AP (Mortise) - to look at the joint space, see the fracture lines and if it is comminuted

Lateral - to check for anterior/posterior displacement of the fragments

Question 18

Radiographic appearance of Pilon Fracture

Answer 18

possible comminuted fractures, reduced joint space