imaging of the lower limb- foot + ankle

Question 1

What are some body movements relating to the lower limb?

Answer 1

-Dorsiflexion
-Plantar flexion
-Inversion
-Eversion

Question 2

Dorsiflexion

Answer 2

Pointing toes upwards towards the tib/fib- used more in positioning

Question 3

Plantar flexion

Answer 3

pointing toes down and away from the tib/fib

Question 4

Inversion

Answer 4

turning a body part in-wards- reason for x-ray

Question 5

Eversion

Answer 5

turning a body part outwards.

Question 6

What are landmarks?

Answer 6

• Palpable anatomy we can use to aid in positioning and centring.

Question 7

Medial malleolus?

Answer 7

Inside ankle

Question 8

Lateral malleolus?

Answer 8

Outside ankle

Question 9

What views are used to x-ray the foot?

Answer 9

• DP, oblique (more common), and lateral.

Question 10

What is the patient position for DP foot?

Answer 10

-Patient seated on x-ray table
-Hips and knees flexed
-Plantar aspect of foot placed on image receptor
-Ensure anatomy is with IR boundaries
-Ensure foot is perfectly flat/straight
-Unaffected leg is abducted away from affected leg

Question 11

What is the centring point for a DP foot?

Answer 11

-Central ray with 15 degrees cranial angulation (can use 15 degree pad with vertical beam.
-Cuboid-navicular joint

Question 12

How do you collimate a DP foot?

Answer 12

-Include all bones of the foot
-Include all skin borders
-Include the malleoli (can be hidden injuries there)

Question 13

What are some essential image characteristics of a foot DP?

Answer 13

-Foot is not internally or externally rotated
-tib/fib are straight and not superimposed over foot (do not over flex the knee)
-Physical Marker
-No artefacts

Question 14

What is the patients position for a oblique foot?

Answer 14

-Place foot in unexposed part of image receptor.
-From DP Position, patient leans affected leg medially so that sole of foot is approx. 30 - 45° to image receptor.
*Can utilise 45° radiolucent pad under lateral aspect of foot
*Unaffected leg is abducted away from affected leg

Question 15

How do we centre for an oblique foot?

Answer 15

*Centred over cuboid-navicular joint.
*Vertical beam (take 15° angle off from DP)

Question 16

How do we collimate for an oblique foot?

Answer 16

-Include all bones of the foot
- Include all skin borders
-Clear view though intertarsal and tarsometatarsal joints
-Good exposure from toes to tarsus
-Include the malleoli (can be hidden injuries there)

Question 17

What is the patient position for a lateral foot?

Answer 17

*Patient lies on affected side
*Hips and knees flexed
*Lateral aspect of affected foot in contact with image receptor
*Sole of foot 90° to image receptor

Question 18

What is the centring point for a lateral foot?

Answer 18

*Central ray vertical  to the image receptor
*Bases of MT joints

Question 19

How do you collimate fot a lateral foot?

Answer 19

*Include all bones of the foot
* Include all skin borders
*Clear view though intertarsal and tarsometatarsal joints
*Good exposure from toes to tarsus
*Include the malleoli (can be hidden injuries there)

Question 20

What are some additional views for a foot?

Answer 20

-Weight bearing DP
-Weight bearing lateral
-Tangential.

Question 21

What is a weight bearing DP and lateral?

Answer 21

1.Weight Bearing DP – Why? Can guarantee that the joint will be flat, and gives a clear indication as to what forces affect the joint.
2.Weight Bearing Lateral- Why? See any displacement when weight is on it.

Question 22

What views are used for the hallux (big toe)?

Answer 22

DP, Oblique and lateral.

Question 23

Hallux DP and oblique

Answer 23

• DP and Oblique are same technique as DP and Oblique foot respectively. Centre over the Metatarsophalangeal joint.

Question 24

Hallux lateral

Answer 24

: From the DP position, rotate the foot medially until the medial aspect is in contact with the image receptor.
* Pull the other toes back with a bandage (can improvise with pads or plastic aprons)
If pain in metatarsals then x-ray whole foot.

Question 25

How do you position, collimate and centre for a lateral calcaneum (heel)?

Answer 25

-Patient lies on affected side
-Leg is externally rotated until malleoli are superimposed
-Ankle remains in dorsiflexion
-Lateral aspect of foot in contact with image receptor
-Heel in middle of unexposed side of image receptor
-Central ray vertical  to the image receptor & 2.5cm distal to medial malleolus
-Similar to lateral ankle just centred differently

Question 26

How do you position, collimate and centre for an axial calcaneum (heel)?

Answer 26

-Patient seated on x-ray couch with legs extended
-Internally rotate affected ankle until medial and lateral malleoli are equidistant from image receptor
-Place heel at bottom of image receptor
-Dorsiflex foot so that sole of foot is perpendicular to image receptor
-Central ray with 40 ° cranial angulation
-At level of base of 5th MT in midline of plantar aspect of heel
-Primary aim is the elongate the calcaneum

Question 27

What are the main projections for an ankle x-ray?

Answer 27

Ap Mortise & Lateral-
AP Mortise- aim is to see all 3 joints of the ankle.
lateral malleolus- very end of fibula
Medial malleolus- end of tibia
Lateral- need to include base of 5th metatarsal.

Question 28

How do we carry out an AP Mortise ankle?

Answer 28

-Patient seated on x-ray couch with legs extended
-Unaffected leg abducted away from affected leg
-Posterior aspect of affected ankle placed on image receptor, with heel at bottom
-Medially rotate affected ankle until medial and lateral malleoli are equidistant to the image receptor
-Dorsiflex foot so that sole of foot is perpendicular to image receptor
Central ray vertical  to the image receptor
Midway between both malleoli

Question 29

What are some essential image characteristics for an AP Mortise ankle

Answer 29

-Include distal 3rd of tib/fib
-Clear view between the fibula, tibia and talus to create a clear “mortice” view.
-Soft tissue borders laterally.
-Sufficient dorsiflexion so the calcaneum is not superimposed over lateral malleolus and joint space.
-Sufficient internal rotation for proper visualisation of the distal tibiofibular joint.
-AP demonstrates a true representation of the joint whereas the mortise ‘clears’ the joint space

Question 30

How do we position for a lateral ankle?

Answer 30

-Patient lies on affected side
-Affected leg is externally rotated until med and lat malleoli are superimposed
-Ankle remains in dorsiflexion
-Lateral aspect of foot in contact with image receptor
-Heel at bottom of unexposed side of image receptor
-Small wedge pad placed under forefoot

Question 31

How do we centre for a lateral ankle?

Answer 31

Central ray vertical  to the image receptor
Level of medial malleolus

Question 32

What are some essential image characteristics for a lateral ankle?

Answer 32

-Distal 3rd of tib/fib
-Superimposition of medial and lateral trochlear surfaces of the talus (creating talar dome)
-Base of 5th MT visualised on lateral border of image/collimation.
-Assess talar dome and position of fibula to work out if your patient is under or over rotated.

Question 33

What are some additional ankle projections?

Answer 33

-Internal and External Obliques
-Weight Bearing AP & Lateral
-Horizontal Beam (If patient unable to mobilise)