Indications for imaging
Trauma, degenerative conditions, bone pain.
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Anatomy Demonstrated
Ankle joint, distal tibia and fibula and proximal talus.
Ankle Rt AP Anatomy
Meschan, I. 1955 An Atlas of Normal Radiographic Anatomy
Saunders, London
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Basic Patient Position
There are two variations, a) the true AP and b) the oblique. the
true AP does not separate the distal tibio-fibula joint the
oblique does.
The patient lies supine on the table legs extended, long
axis of the limb in line with the long axis of the table, the
foot is dorsi flexed to bring the plantar aspect 90 to the film.
a) The distal tibial and fibula malleoli are not
equidistant from the film and the long axis of the foot is
positioned vertically.
b) The distal tibial and fibula malleoli are equidistant
from the film and the long axis of the foot is positioned
rotated medially approximately 10 degrees.
Note that the foot is extremely mobile and rotating the foot
inwards does not rotate the tibia and fibula, when rotating the
ankle the whole leg has to be rotated.
Ankle AP Lt Patient Position
Meschan, I. 1955 An Atlas of Normal Radiographic Anatomy
Saunders, London
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Radiation protection
Direct lead rubber gonad protection using a "half
apron".
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Central Ray
The vertical central ray is centered midway between the
malleoli.
*This centering point maximally visualises the talo-tibia joint
space, to include the distal tibia and fibula, the collimation
has to extend well below the plantar surface of the foot, if the
joint is positioned on the lower half of the cassette there will
be no collimation visible distally.
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Exposure Factors
| Kv |
mAS |
FFD (cm) |
Grid |
Focus |
AEC |
Cassette |
| 60 |
5 |
100 |
No |
Fine |
No |
18 x 24 cm |
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Evaluation of the Image
ID and markers must be present and correct in the appropriate
area of the film
Evidence of collimation on three* sides equally around the
centering point.
Limits of the examination, superiorly the distal portion of the
tibia and fibula, laterally and medially the skin surfaces of
the ankle.
a) true AP tibio talo joint space should be open and the
distal fibula will overlap the medial tibial
expansion.
b) oblique tibio talo and tibio fibula joint spaces should
be open and the distal fibula will not overlap the medial tibial
expansion.
Optimal exposure should penetrate all the bone structures
and contrast should be low enough to visualise fully the bone
and soft tissue structures.
Ankle AP Lt, Radiograph
http://www.vh.org/Providers/TeachingFiles/NormalRadAnatomy/Images/
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Related Projections
Tibia and fibula AP and lateral.
Tarsal bone projections.
Foot DP and DP Oblique.
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Additional modalities
CT
MRI
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