imaging of lower limb- exc. foot + ankle

Question 1

What are the standard projections for Tibia/fibula?

Answer 1

-Anterior-Posterior (AP)
-Lateral

Question 2

How do you positon for an AP Tib/Fib?

Answer 2

*Patient seated on x-ray couch with legs extended
*Posterior aspect of leg in contact with image receptor (IR)
*Rotate affected leg until malleoli and femoral condyles are equidistant from IR
*Dorsiflex foot so that sole of foot is perpendicular to image receptor
*Position leg on image receptor to ensure both knee and ankle joint included
*Abduct unaffected leg away

Question 3

How do we centre for an AP TIB/FIB

Answer 3

-Central ray vertical to the image receptor
-Midpoint between ankle and knee joint

Question 4

What are some essential image characteristics for an AP TIB/FIB?

Answer 4

-Try to include both the knee and ankle joints on one radiograph. (Position IR so it runs diagonally with tib/fib)
-If not possible do 2 separate images that include both joints on but have overlap between radiographs.
-Include lateral and medial soft tissue borders.

Question 5

How do we position a patient for a lateral TIB/FIB?

Answer 5

-Patient lies on affected side
-Lateral aspect of leg in contact with IR
-Hip and knee slightly flexed
-Ankle remains in dorsiflexion
-Malleoli and femoral condyles superimposed
-Unaffected limb moved away and supported
-Position leg on IR to ensure both knee and ankle joint included

Question 6

How do we centre for a lateral TIB/FIB?

Answer 6

-Central ray vertical to the image receptor
-Midpoint between ankle and knee joint

Question 7

Essential image characteristics for lateral TIB/FIB?

Answer 7

• Try to include both the knee and ankle joints on one radiograph. (Position IR so it runs diagonally with tib/fib)
• If not possible do 2 separate images that include both joints on Hobut have overlap between radiographs.
• Include lateral and medial soft tissue borders.

Question 8

What are some additional projections for TIB/FIB?

Answer 8

• Internal (rotate the leg from the hip medially 45°) (Internal rotation)
• External Oblique (rotate the leg from the hip laterally 45°) (Exter
• Specific Orthopaedic requests (centre over specific ring on Ilizarov Frame)

Question 9

What are some possible clinical indications for a knee x-ray?

Answer 9

• Osteoarthritis
• Pain/swelling/unable to Weight bear
• Trauma
• Follow-up orthopaedic assessment

Question 10

What are the standard knee projections?

Answer 10

-AP
-lateral

Question 11

How do we position for an AP knee?

Answer 11

Ø Patient seated on x-ray couch with legs extended
Ø Unaffected limb abducted
Ø Posterior aspect of knee in contact with image receptor
Ø Rotate affected leg until femoral condyles are equidistant from image receptor
Ø Patella centralised between femoral condyles

Question 12

how do we centre for an AP knee

Answer 12

Ø Central ray vertical to the image receptor
Ø 2.5cm below apex of patella
Ø 5º cranial angle may be used to open joint space

Question 13

Essential characteristics for an AP knee?

Answer 13

• Patella must be central within the distal femoral condyles.
• Include distal 3rd of femur and proximal 3rd of tib/fib.
• Include soft tissue borders included medially and laterally (on slim patients).

Question 14

How do you position a patient for a lateral knee?

Answer 14

• Patient lies on affected side
• Unaffected limb in front or behind affected limb and supported with pads etc
• Affected knee flexed 45º
• Lateral aspect of knee in contact with IR
• Femoral condyles superimposed
• Patella perpendicular to image receptor
• Pad placed under ankle of affected side to bring tibia parallel to IR

Question 15

What is the centring point for a lateral knee?

Answer 15

Ø Central ray vertical to the image receptor
Ø 2.5cm below and behind apex of patella
Ø 5º cranial angle may be used

Question 16

Essential image characteristics for lateral knee?

Answer 16

• Patella is projected clear of femur to demonstrate joint space.
• Femoral condyles are superimposed.
• Prox. Tibiofibular joint not fully visualised
• Include distal 3rd of femur and proximal 3rd of tib/fib.
• Include soft tissue borders included anteriorly and posteriorly (on slim patients).

Question 17

what are some additional projections for a knee?

Answer 17

• Intercondylar notch (tunnel view)
• Stress views – AP + Lateral
• Weight bearing – AP (+ lateral)
• Horizontal beam lateral
• AP medial + lateral oblique
• PA patella
• Skyline patella

Question 18

indercondylar notch (tunnel view)

Answer 18

assess for loose bodies

Question 19

Stress views – AP + Lateral –

Answer 19

Assess laxity and compartmental degeneration (OA)

Question 20

Weight bearing – AP (+ lateral)

Answer 20

Assess true alignment & degeneration of joint using weight of pt. & gravity

Question 21

Horizontal beam lateral

Answer 21

trauma – to avoid exacerbating injuries & demonstrate lipohaemoarthrosis.

Question 22

AP medial + lateral oblique

Answer 22

Demonstrate bones/joint at different angles to assess for injury – patella lat/med borders well demonstrated on obliques.

Question 23

PA patella

Answer 23

Demonstrates patella more clearly as closer to IR therefore no magnification.

Question 24

Skyline patella

Answer 24

demonstrate infero patella-femoral joint space

Question 25

Femur possible clinical indications?

Answer 25

• Trauma/Query Fracture
• Query Pathology (Metastasis) (Common place for malignancies)
• Follow-up imaging (fracture clinic/outpatients)

Question 26

what are common projections for a femur?

Answer 26

-AP
-Lateral

Question 27

How do you position a patient for an AP femur?

Answer 27

• Patient supine with legs extended
• Abduct unaffected leg
• Ensure pelvis is not rotated
• Posterior aspect of femur in contact with IR
• Medially rotate affected limb to centralise patella between femoral condyles (also corrects foreshortening of femoral neck)
• Position leg on IR to ensure both knee and hip joint included if possible
• Hard to fit a patients entire femur on an x-ray.
• Straighter patella is, the straighter the hip will be.

Question 28

What is the centring point for an AP Femur?

Answer 28

Ø Central ray vertical to the image receptor
Ø Centre mid-thigh/femur

Question 29

Essential image characteristics for AP Femur?

Answer 29

• Both hip and knee joints should be included where possible.
• In practice, usually requires hip down and knee up view (2 radiographs)
• What might you consider between the radiographs?

Question 30

How do you position a patient for a lateral femur?

Answer 30

Ø Upper femur – patient lies on affected side and rolls posteriorly approx. 15º with pillows/pads for support.
Ø Unaffected limb behind affected limb with flexed knee to place foot flat on table (and support)
Ø Affected knee flexed to bring patella surface perpendicular to image receptor/table
Ø Femoral condyles superimposed
Ø Position leg on IR to ensure both knee and hip joint included if possible

Question 31

what is the centring point for a lateral femur?

Answer 31

• Central ray vertical to the image receptor
• Centre mid-thigh

Question 32

Essential image characteristics for lateral femur?

Answer 32

• Both hip and knee joints should be included where possible.
• In practice, usually requires hip down and knee up view (2 radiographs)

Question 33

what are some potential problems when it comes to imaging a femur?

Answer 33

• Imaging whole femur on one image- density of knee is different to hip. Hard to get exposure factors that can penetrate the hip but not the knee.
• Differences in densities
• Two images - ? Exact same plane?
• What if patient cannot move? Additional projections? May have to use a horizontal beam.

Question 34

Describe two radiographic projections to demonstrate the left ankle of an ambulant patient (10 marks)

Answer 34

2 projections of the left ankle:
Anterio-posterior (AP Mortise) 
l Patient seated on x-ray table with affected leg extended 
l Place heel of affected ankle at the bottom of one half of the cassette 
l Internally rotate ankle  until medial + lateral malleoli equidistant from cassette 
l Dorsiflex foot  so that sole of foot is perpendicular to the cassette 

AP continued
u Central ray vertical to the cassette 
u Centre midway between medial + lateral malleoli 
u Collimation to include PROX lower 1/3 tibia, DIST proximal MT’s, MED + LAT soft tissue borders 
u Place left anatomical marker onto cassette 
u Place lead rubber apron onto patient’s lap 

Lateral 
l Patient lies on affected side 
l Place patient’s heel at the bottom of unexposed half of the cassette 
l Ankle remains in dorsiflexion 
l Affected leg is externally rotated  until medial + lateral malleoli are superimposed 
l Central ray vertical to the cassette 
l Centre over medial malleolus 