rad tech - lower extremity and knee

are AP toes a dorsoplantar or plantodorsal projection?

dorsoplantar

Dorsoplantar (AP) Axial Toes

Patient Position

•  Sitting or lying on X-ray table

•  Leg of interest on table

Part Position

•  Plantar surface of foot on IR

•  No rotation of foot

•  Metatarsal of interest centered to IR

CR

•  10-15◦ toward calcaneus

• Centered to MTP of interest

Collimation 

• Include entire toe and at least ½ of metatarsal

Evaluation Criteria of AP toes

 Digits and minimum of distal ½ of metatarsal demonstrated

 No overlap of soft tissues

 IP and MTP joints appear open

 No rotation of foot

 Equal concavity of phalanges

 Optimal exposure factors

Dorsoplantar (AP) Oblique Toes

Patient Position

 Same as AP

Part Position

 Foot is rotated 30-45◦ medially for 1st- 3rd & laterally for 4th & 5th

 May need to pull other toes out of the way

 Can use tape or rubber tubing etc

CR

 CR is perpendicular to MTP of interest

Collimation

 Same as AP

Evaluation Criteria for oblique toes

 Digits and minimum of distal ½ of metatarsal demonstrated

 IP and MTP joints appear open.

 Increased concavity on one side of shaft

 Heads of metatarsals with no or minimal overlap

 Other toes do not obscure toe of interest

 Optimal exposure factors

Lateral Toe

Patient Position

 Same as AP & oblique

Part Position

 1st ,2nd & 3rd rotated onto medial surface

•  Lateromedial projection

 4th & 5th rotated onto lateral surface

•  Mediolateral projection

CR

 CR perpendicular to PIP or IP ( 1st toe)

Collimation

 Same as AP & oblique

Evaluation Criteria for lateral toes

 Digits presented in true lateral position

 Anterior surface is concave

 IP and MTP joints appear open

 Digit free of superimposition

 Optimal exposure factors

Dorsoplantar (AP) Axial Foot

Patient Position

 Sitting or lying on table

 Planter surface of foot on the table

 May be performed with patient standing on IR*

 NOTE: CR angle may need to be increased when patient is standing

Part Position

 Plantar surface flat against IR

 No rotation

CR

 Angle approx. 10◦ toward heel; centered to base of 3rd metatarsal

 Patients with a high longitudinal arch require a greater angle

o 15-degrees

 A low longitudinal arch requires less angle

o 5-10 degrees

Collimation

• Include entire foot

Evaluation Criteria for AP foot

 Entire foot visualized

 No rotation of metatarsals

 MTP joints generally open

 Bases of 1st & 2nd metatarsals separated

 Bases of 3rd- 5th overlap

 Joint space between 1st & 2nd cuneiform is open

 Distal phalanges not overexposed

o May need to use a compensating filter to maintain an uniform image exposure

Dorsoplantar (AP) Oblique Foot

Patient Position

 Same as AP axial

Part Position

 Foot is rotated medially 30-40 degrees

 Dorsum of foot near parallel to IR

 Low arch= less rotation; high arch= more rotation

CR

 Perpendicular to base of 3rd metatarsal

Collimation

• Include entire foot and ankle joint

Evaluation Criteria for oblique foot

 Entire foot visualized

 Third through fifth metatarsal bases free of superimposition

 Bases of 1st – 2nd are overlapped

 Tuberosity demonstrated at base of fifth metatarsal

 Sinus tarsi visualized

 Cuboid-cuneiform joint space is open

is a lateral foot mediolateral or lateromedial

mediolateral

Lateral Foot

Patient Position

 Patient lies on affected side or standing at upright IR

 If recumbent: Flex affected knee 45-degrees

 Other leg is placed behind

Part Position

 Foot in a lateral position with lateral surface against IR

 Dorsiflex foot and place plantar surface perpendicular to IR

CR

 perpendicular to medial cuneiform

Collimation

to include at least 2.5 cm of the ankle

Evaluation Criteria for lateral foot

 Entire foot visualized

 Talar domes are superimposed and tibiotalar joint demonstrated

 Metatarsals are nearly superimposed

 Base of the fifth metatarsal visible

 Distal fibula superimposed on posterior tibia

 Long axis of foot forms a 90 degree angle with the tib/fib

AP Ankle

Patient Position

 Sitting or lying on table

o Can be standing

 Affected leg extended on table

Part Position

 Foot is dorsiflexed to form a right angle to tib/fib

 Note: we don’t force this if there is an injury

 Intermalleolar line forms a 15-20 degree angle to the IR

CR

 Perpendicular to a point midway between malleoli

Collimation

Include approx of 1/3 tib/fib, talus and proximal metatarsals

Must include base of 5th metatarsal

Evaluation Criteria of AP ankle

 Distal ⅓ of tibia and fibula demonstrated

 Proximal ½ of metatarsals included

 Medial and superior aspect of Mortise joint open

 Lateral distal tibia+ lateral talus superimposed over fibula

 Closed lateral Mortise joint

AP Oblique ( Mortise) Ankle

Patient Position

 Same as AP

Part Position

 Foot is not dorsiflexed, allow it to remain extended (visualize the base of the 5th MT).

 Entire lower limb is rotated 15-20◦ to place intermalleolar line parallel to IR

CR

 Perpendicular to midway b/w malleoli

Collimation

• Include distal tib/fib (⅓ ) and proximal metatarsals, especially the base of the 5th medially

Evaluation Criteria for AP mortise ankle

• Entire ankle mortise open

• Medial , lateral & superior aspects

• Distal ⅓ of tibia and fibula demonstrated

• Little, if any, overlap of distal tib/fib

• Proximal ½ of metatarsals included

• Optimal exposure factors

Lateral Ankle

Patient Position

 Lying on affected side with lateral ankle against IR

o Can be standing

Part Position

 Foot dorsiflexed to place foot at right angle to tib/fib

 Affected ankle in a true lateral

 Lateral malleolus located 1 cm posterior to the medial malleolus

CR

 perpendicular to medial malleolus

Collimation

 to include entire ankle joint, distal tib/fib and base of 5th metatarsal

 especially the base of the 5th

Evaluation Criteria of lateral ankle

 Entire talus and calcaneus visualized

 Base of 5th metatarsal demonstrated

 Lateral malleolus superimposed over posterior half of tibia

 Talar domes superimposed & tibiotalar joint is open

 Optimal exposure factors – visualize the distal fibula through the talus.

 Should see anterior pretalar and posterior pericapsular fat pads

• Note: Foot must be dorsiflexed 90° for anterior pretalar fat pad to properly demonstrated

is this lateral ankle over or under rotated

under

is this lateral ankle over or under rotated

over rotated

AP Tibia & Fibula

Patient Position

• Lying on x-ray table

• Affected leg extended

Part Position

• Entire affected limb is in a true AP

• Affected foot is dorsiflexed 90o

CR

• perpendicular to the IR; centered to midshaft region of tib/fib

Collimation

• Knee to ankle must be included

• Usually requires the IR to be placed diagonally

• May also require increase SID

Evaluation Criteria for AP Tib/Fib

• Entire tibia and fibula demonstrated

• Knee and ankle joints demonstrated

• Partial superimposition of fibula and tibia at proximal and distal ends

•  Due to divergence of the beam, neither knee nor ankle joint is fully open

• Optimal exposure factors

Lateral Tibia & Fibula

Patient Position

• Lying on affected side

Part Position

• Both knee and ankle are in a true lateral position

• Patellar surface perpendicular to IR

CR

• perpendicular to IR & centered to mid tib/fib

Collimation

• to include both joints

Evaluation Criteria for lateral tib/fib

• Entire tibia and fibula demonstrated

• Knee and ankle joints demonstrated

• Proximal head of fibula superimposed by tibia

• Distal fibula superimposed over posterior half of tibia

• Optimal exposure factors

Plantodorsal Axial Calcaneus

Patient Position

• Sitting or lying on table

• Affected leg extended

•  Foot is dorsiflexion

Part Position

• Plantar surface of foot should be 90o to the IR

• Patient may hold foot in place with “strap”

CR

 angled 40o toward the plantar surface (cephalad)

• Centered to the base of the third metatarsal

Collimation

• include entire calcaneus + ankle joint

Tip: Imagine a line between the base of the fifth metatarsal and the lateral malleolus ;CR should be parallel to this line (Angle less if foot is flexed more, angle more if not flexed enough)

Evaluation Criteria of plantodorsal axial calcaneous

• Entire calcaneous visualized

• Including open talocalcaneal joint space

• No rotation

• Base of the 5th MT seen laterally

• Sustentaculum tali visible in profile medially

Lateral Calcaneus

Patient Position

• Lying on affected side

Part Position

• Affected foot/ankle in a true lateral position

• Lateral malleolus is slightly (1 cm) posterior to medial malleolus

• Foot dorsiflexed 90o

CR

• is perpendicular to IR; centered 2.5cm (1″) inferior to medial malleolus

Collimation

• to include ankle joint and entire calcaneus

• Note: if lateral calcaneus is performed only to rule out heel spurs, collimation may be closer

AP Knee

Patient Position

• Supine with no rotation

• Affected knee extended ( can be standing)

Part Position

• Knee is in a true AP position

• Femoral epicondyles are in profile

• A line drawn between the epicondyles is parallel to the IR

• Leg internally rotated ≈ 3-5°

CR

• CR is parallel to the tibial plateau

• Amount of CR angle required depends on thickness of patient’s thighs (See below)

• CR is centered 1.25 cm inferior to the apex of the patella

Collimation

• Include about ¼ of distal femur + proximal tib/fib

Evaluation Criteria for AP knee

• Femorotibial joint space open

• Femoral condyles are symmetrical

• Femoral epicondyles in profile

• Knee joint centered to collimation field

• Articular facets of tibia on end

• Intercondylar eminence centered within the fossa

• Intercondylar fossa is barely seen

• Approx ½ of fibular head superimposed by tibia

• Head of fibula approx 1.25 cm from tibial plateau

• Patella sits slightly lateral to midline

Lateral Knee ( mediolateral)

Patient Position

• Lying on affected side

• Unaffected leg either behind or in front of affected leg

• (can be standing)

Part Position

• Affected knee is flexed 20-30°

• Some texts suggest only 10- 15 °

• Use caution if flexing injured knee; may leave knee extended or partially flexed

• Knee in a true lateral

• Femoral epicondyles are superimposed

• Patellar surface is perpendicular to IR

CR

• CR is angled 5-7° cephalad; centered 2.5 cm inferior to medial epicondyle of femur

• ≤ 5° for taller, thinner patients

• ≥ 7 ° for shorter patients with wider pelvis

• Tip: rotate collimator so CR is directed across the femoral condyles

Collimation

• Include distal femur/proximal tib/fib

NOTE: May use “boomerang” filter for better soft tissue demonstration

Evaluation Criteria for lateral knee

• Femoral condyles superimposed

•  Determined by rotation

•  Use abductor tubercle to determine if medial condyle is anterior/posterior

• Distal articular surfaces of femoral condyles superimposed

•  Determined by adequate CR angle

• Patella in profile (indicates no rotation)

• Patellofemoral joint space open

• Fibular head is partially superimposed by tibia

• Soft tissues well demonstrated

• Filter used

Medial & Lateral Oblique Knee

 @ QEH not part of knee protocol; only performed if specifically requested

• Knee is rotated 45° medially & then 45° laterally

• Both obliques acquired

• Centering, CR angle & Collimation are the same as an AP Knee

Medial Oblique knee evaluation criteria

• Proximal tibiofibular joint open

• Demonstrates lateral femoral and tibial condyles

• Half of patella superimposed over medial femoral condyle

Lateral Oblique knee evaluation criteria

• Fibula superimposed over mid tibia

• Demonstrates medial femoral and tibial condyles

• Half of patella superimposed over lateral femoral condyle