Ankle Lateral (Lateromedial) is a radiography positioning projection of the Lower Extremity. Patient lateral on non-affected side, medial ankle on IR. CR perpendicular. SID 40". The centering point is located ankle joint: medial malleolus level (Bontrager), or 1/2 inch above the lateral malleolus (Merrill's). Medial border of foot on IR. The central ray is perpendicular to the IR, through the ankle joint: to the medial malleolus (Bontrager), or entering 1/2 inch above the lateral malleolus (Merrill's). Medial border on IR. Image-quality criteria include tibiotalar joint open with an even joint space, no rotation: distal fibula over the posterior half of the tibia. A sample technique is 70 kVp with DR 1.25 or CR 2.2 mAs, at an SID of 40 inches (102 cm).
Anatomy demonstrated
- Distal fibula over the posterior half of the tibia.
- Talocrural articulation visible.
- Distal tibia and fibula superimposed in a true lateral.
- Medial and lateral talar domes superimposed (Merrill's).
Patient preparation
- WARNING: with possible spinal injury or severe trauma, do not attempt to move the patient; do not rotate a severely injured part or remove splints (Bontrager). Merrill's: do not attempt true AP or lateral positioning of a severely injured limb; take two projections 90 degrees apart, moving it as little as possible, and move the IR and tube if the patient cannot reach the position.
- Verify patient identity using two identifiers.
- Remove footwear, socks, and any radiopaque foot jewelry.
- Position the patient lateral recumbent on the non-affected side.
- Turn the affected foot inward (medially) with medial border on IR.
- Foot at 90 degrees to the leg. Merrill's keeps the leg extended, with knee support if needed.
Position & centering point
Ankle joint: medial malleolus level (Bontrager), or 1/2 inch above the lateral malleolus (Merrill's). Medial border of foot on IR.
Central ray
Perpendicular to the IR, through the ankle joint: to the medial malleolus (Bontrager), or entering 1/2 inch above the lateral malleolus (Merrill's). Medial border on IR.
Exposure / technique
- kVp
- 70
- mAs
- DR 1.25 / CR 2.2
- SID
- 40" (102 cm)
- Notes
- Position patient on non-affected side. Merrill's keeps the leg extended, with support under the knee if needed. Sample technique: DR 1.25 / CR 2.2 mAs at 70 kVp, 40 in SID, for a 7 cm part. Adjust for your equipment.
kVp and mAs are sample values. Use caution when applying them in your department.
Image-quality criteria
- Tibiotalar joint open with an even joint space.
- No rotation: distal fibula over the posterior half of the tibia.
- Talus, calcaneus and the 5th metatarsal tuberosity in lateral profile.
- Distal tibia and talus well visualized.
- Bone trabeculae sharp, no motion blur.
- Collimation: 1 inch on the sides, 8 inches lengthwise (Merrill's).
Common errors
- 1 Rotation moves the fibula off the posterior half of the tibia.
- 2 Tibiotalar joint not open with a uniform joint space.
- 3 CR not directed through the ankle joint.
- 4 Leaving the foot plantar flexed makes a true lateral harder to hold.
Clinical indications
- Fractures, dislocations and joint effusions, as for the mediolateral lateral.
- Alternative to the mediolateral: less comfortable, but a true lateral may be easier (Bontrager).