| Name of projection | Ankle - Lateral |
| Area Covered | The distal third of the tibia and fibula, navicular, cuboid, base of the 5th metatarsal, calcaneus |
| Pathology shown | Displacement of the anterior pretalar fat pad or the posterior pericapsular fat pad indicates joint effusion |
| Radiographic Anatomy | Ankle Radiographic Anatomy |
| IR Size & Orientation | 18 x 24cm
Portrait |
| Film / Screen Combination | Detail
(CR and DR as recommended by manufacturer) |
| Bucky / Grid | No |
| Filter | No |
| Exposure | 60 kVp
3.2 mAs |
| FFD / SID | 100cm |
| Central Ray | Directed to the medial malleolus
Perpendicular to the IR |
| Collimation | Centre: The medial malleolus
Shutter A: Open to include the distal third of the tibia and fibula & the calcaneus
and proximal metatarsals
Shutter B: Open to include the calcaneus, proximal metatarsals,anterior and posterior skin margins |
| Markers | Proximal and Anterior
Marker orientation AP |
| Shielding | Gonadal (check your department's policy guidelines) |
| Respiration | Not applicable |
| Positioning | Mediolateral (this is usually easier for the patient to achieve)
- Patient is recumbent
- Rotate the leg and foot of the affected side so that the lateral foot surface is parallel to (and against) the IR
- Leg can be bent approxiately 45° for patient comfort, or done with a straight leg
- The lower leg should be parallel to the table in most cases, however if not, then the foot and IR can be elevated on sponges to achieve this desired position
- Ask the patient to dorsiflex their foot, if possible, so that the plantar surface is at 90° to the lower leg. (This will best show the anterior pretalar fat pad)
- Position the plantar surface so it is perpendicular to the lR
- Align ankle so malleoli are superimposed
|
Critique
| Positioning
- A lateral position is achieved as evidenced by
- The talar domes are superimposed
- The tibiotalar joint space is shown open
- The distal fibula is superimposed by the posterior tibia
- The foot is dorsiflexed 90° to the lower leg to show any fat pad displacement
Area Covered
- The distal third of the tibia and fibula, navicular, cuboid, base of the 5th metatarsal, calcaneus are visualised
Collimation
- Centre: The medial malleolus
- Shutter A: Open to include the distal third of the tibia and fibula & the calcaneus
and proximal metatarsals
- Shutter B: Open to include the calcaneus, proximal metatarsals,anterior and posterior skin margins
Exposure
- Bony trabecular patterns and cortical outlines are sharply defined
- Soft tissues are visualised
- Correct contrast and density to show the fat pads of the foot and ankle (posterior pericapsular and anterior pretalar fat pads)
|
| Special Notes | The effect of incorrect lower leg angle
i.e. Lower leg not being parallel to table
- Talar domes will not be superimposed, one will show more superior to the other. If the proximal tibia is higher than the distal tibia then the lateral talar dome will appear higher (more proximal) than the medial talar dome. If the distal tibia is higher than the proximal tibia then the medial talar dome will appear higher (more proximal) than the lateral talar dome.
- Tibia talar joint will not show open
The effect of poor foot and ankle positioning
i.e. Lateral foot surface not being parallel to IR
- Talar domes will not be superimposed, one will show more anterior to the other. If the leg and foot are externally rotated too far (that is, the heel is raised too far) then the medial talar dome is more anterior than the lateral talar dome. If the toes are raised too much (that is, the heel lateral heel is pressed against the IR) then the lateral talar dome is more anterior than the medial talar dome.
- Tibia talar joint will not show open
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