Lower limb Flashcards
Preparation
- Ensure your room is clean, tidy and safe. As with other exams this is the key
- Set the appropriate preliminary exposure factors and programme on the software.
- Set up the equipment you need (i.e. wall bucky, free detector or cassettes).
- Get your markers out and ready to use.
- Wash your hands. Follow infection control protocols.
- Ensure there are no hazards
Exposure factors: foot
60kV 2mAs
Exposure factors: ankle
60kV 2.5mAs
Exposure factors: Tib/fib
60Kvs 4mAs
The foot: possible clinical indications
- OA/Pain
- Trauma
- Stress fracture?
- Osteomyelitis
- Foreign body?
- Follow-up imaging
- Congenital abnormalities (with justification of why imaging will help)
- Hallux vagal (pre-operative assessment)
Dorsoplantar foot (DP) technique
- Patient seated on x-ray table
- Hips and knees flexed
- Plantar aspect of foot placed on IR
- Ensure anatomy is with IR boundaries
- Ensure foot is perfectly flat/straight
- Unaffected leg is abducted away from affected leg
- Central ray with 15 degrees cranial angulation (can use 15-degree pad with vertical beam)
- Cuboid-navicular joint
Essential image characteristics of Dorsoplantar foot (DP) technique
- Include all bones of the foot
- Include all skin borders
- Include the malleoli (can be hidden injuries there)
- Foot is not internally or externally rotated
- Tib/fib are straight and not superimposed over foot (do not flex the knee)
- Physical markers
- No artefacts
Oblique foot technique: patient position
- 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 degrees to IR
- Can utilise 45 degrees radiolucent pad under lateral aspect of foot
- Unaffected leg is abducted away from affected leg
- Centred over cuboid-navicular joint
- Vertical beam (take 15 degrees angle off from DP)
Essential image characteristics of Oblique foot technique
- Include all bones of the foot
- Include all skin borders
- Clear view through intertarsal and tarsometartarsal joints
- Good exposure from toes to tarsus
- Include the malleoli (can be hidden injuries there)
- Physical markers
- No artefacts
- No over or under internal rotation (MTs too superimposed or not superimposed)
Lateral foot technique: Patient position
- Patient lies of affected side
- Hips and knees flexed
- Lateral aspect of affected foot in contact with image receptor
- Sole of foot 90 degrees to IR
Lateral foot technique: Centring point
- Central ray vertical to the IR
- Bases of MT joints
Essential image characteristics: Lateral foot technique
- Include all bones of the foot
- Include all skin borders
- Clear view through intertarsal and tarsometartarsal joints
- Good exposure from toes to tarsus
- Include the malleoli (can be hidden injuries there)
- Physical markers
- No artefacts
- No over or under internal rotation (MTs too superimposed or not superimposed)
Additional views: Foot technique
Weight Bearing DP – Guaranteed joint is going to be flat, and gives clear indication as to what forces affect the joint
Weight Bearing Lateral- See any displacement when weight is on it.
Tangential- Might be able to see where the foreign body is.
Hallux: DP, Oblique and Lateral
- DP and Oblique are same technique as DP and Oblique foot respectively. Centre over the Metatarsophalangeal joint.
- Lateral: 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.
Calcaneum: possible clinical indications:
Injury (fall from a height landing on feet)
Pain/Swelling
Follow up (fracture clinic)
Query Osteomyelitis
Query Foreign Body
Query bone pathology (cyst)
(No longer X-ray for calcaneal spurs in many Trusts as there is no surgical solution)
Lateral calcaneum: Patient position
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
Axial calcaneum: Patient position
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
Ankle
- Anterior-posterior (ap)/ AP Mortise
- Lateral
Ankle: possible clinical indications
OA/Pain
Trauma/? Bony Injury (E.g. Inversion injury)
Follow-up assessment (fracture clinic)
? Foreign Body
Swelling/Hot to touch? Septic Arthritis
Fall from Height
Thoracic pain following fall…what is the correlation?
AP mortise ankle: Patient position
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
AP mortise ankle: Centring point
Central ray vertical to the image receptor
Midway between both malleoli
Essential image characteristics: AP mortise ankle
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
Lateral ankle: Patient position
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
Lateral ankle: Centring point
Central ray vertical to the image receptor
Level of medial malleolus
Lateral ankle: Essential image characteristics
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.
Additional ankle projections
- Internal and External Oblique’s
- Weight Bearing AP & Lateral
- Horizontal Beam (If patient unable to mobilise)
Tibia/fibula
- Anterior-posterior (AP)
- Lateral
- Additional projections
Tib/fib: possible clinical indications
Trauma
Pain ?Bony Pathology
Follow-up imaging (fracture clinic)
Ilizarov frame (Orthopaedics)
? Foreign Body
AP Tib/fib: Patient position
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
Central ray vertical to the image receptor
Midpoint between ankle and knee joint
AP Tib/fib: Essential image characteristics:
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.
Lateral tib/fib: Patient position
- 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
- Central ray vertical to the image receptor
- Midpoint between ankle and knee joint
Lateral tib/fib: Essential image characteristics:
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.
Additional projections: Tib/fib
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)
Knee: possible clinical indications
Osteoarthritis
Pain/swelling/unable to Weight bear
Trauma
Follow-up orthopaedic assessment
AP knee technique
Patient seated on x-ray couch with legs extended
Unaffected limb abducted
Posterior aspect of knee in contact with image receptor
Rotate affected leg until femoral condyles are equidistant from image receptor
Patella centralised between femoral condyles
Central ray vertical to the image receptor
2.5cm below apex of patella
5º cranial angle may be used to open joint space
AP knee technique: Essential image characteristics:
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).
Lateral knee technique:
- 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
Lateral knee technique: Centring point
Central ray vertical to the image receptor
2.5cm below and behind apex of patella
5º cranial angle may be used
Lateral knee technique: Essential image characteristics:
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).
Knee: Additional projections
o Intercondylar notch (tunnel view) – assess for loose bodies
o Stress views – AP + Lateral – Assess laxity and compartmental degeneration (OA)
o Weight bearing – AP (+ lateral) – Assess true alignment & degeneration of joint using weight of pt. & gravity
o Horizontal beam lateral – trauma – to avoid exacerbating injuries & demonstrate lipohaemoarthrosis.
o AP medial + lateral oblique – Demonstrate bones/joint at different angles to assess for injury – patella lat/med borders well demonstrated on oblique’s.
o PA patella – Demonstrates patella more clearly as closer to IR therefore no magnification.
* Skyline patella- demonstrate infero patella-femoral joint space
Patella (supplement radiograph with knee imaging)
Clinical Indication is usually ? Dislocation.
u ?Fracture is a contraindication as may risk making injury worse acquiring radiograph.
Femur: possible clinical indications
Trauma/Query Fracture
Query Pathology (Metastasis) (Common place for malignancies)
Follow-up imaging (fracture clinic/outpatients)
AP femur technique
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
AP femur technique: Centring point
Central ray vertical to the image receptor
Centre mid-thigh/femur
AP femur technique: Essential image characteristics
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?
Lateral femur technique
Upper femur – patient lies on affected side and rolls posteriorly approx. 15º with pillows/pads for support.
Unaffected limb behind affected limb with flexed knee to place foot flat on table (and support)
Affected knee flexed to bring patella surface perpendicular to image receptor/table
Femoral condyles superimposed
Position leg on IR to ensure both knee and hip joint included if possible
Lateral femur technique: Centring point
Central ray vertical to the image receptor
Centre mid-thigh
Lateral femur technique: Essential image characteristics
Both hip and knee joints should be included where possible.
In practice, usually requires hip down and knee up view (2 radiographs)
Femur Potential problems
Imaging whole femur on one image
Differences in densities
Two images -? Exact same plane?
What if patient cannot move? Additional projections?
Describe two radiographic projections to demonstrate the left ankle of an ambulant patient (10 marks)
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
List five additional projections of the knee that may be
undertaken and explain one reason for
undertaking each projection.
(5 x 2 marks)
5 additional projections of the knee and
why:
Intercondylar notch (tunnel view) Investigate fragments/loose bodies within the intercondylar notch
Stress views – AP + Lateral The impact of the joint when directional pressures are applied
Weight bearing – AP (+ lateral) To investigate the impact of gravity on the integrity/alignment of the joint
Horizontal beam lateral To obtain a lateral projection and avoiding causing additional pain/further injury/ to visualise lipohemarthrosis
Skyline patella To investigate/see the patellofemoral joint in profile
State the centring point for the
following:
u AP knee
u Lateral ankle
u DP oblique foot
u AP tibia and fibula
u Etc, etc
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