Radiography of Lower Limb

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Radiography of Lower Limb

• Part I

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Lower Limb

• Foot
• Leg tibia fibula
• Femur (distal and mid)

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Foot

• Divided into three groups
• Phalanges (toes/or digits) 14
• Metatarsals (instep) 5
• Tarsals 7
• Total 26

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Phalanges Toes (Digits) and Metatarsals
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Joints
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Tarsals

1. Calcaneus (os calcis)
2. Talus (astragalus)
3. Cuboid
4. Navicular (scaphoid)
5. 1st, 2nd, and 3rd cuneiforms

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Calcaneus (Os Calcis)

• The largest and strongest bone in the foot
• The posterior portion often called the heel bone
• Inferoposteriorly it has a rough striated process
  called tuberosity
• Tuberosity has two small rounded processes at its
  widest points called the lateral process
  (smallest) and medial process (largest)
• Peroneal trochlea is seen in the lateral aspect
• Sustentaculum tali (support for the talus) is
  seen in the medial aspect

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Calcaneus (Os Calcis)

• Articulations
• Articulate with two bones
• The cuboid anteriorly
• The talus superiorly
• Forms the subtalar (talocalcaneal) joint
• Three articulation facets
• Posterior articular facet (largest)
• Middle articular facet it is the upper portion
  of the sustentaculum tali
• Anterior articulation facet
• Calncaneal sulcus a deep depression b/w
  posterior and middle articular facets which forms
  the sinus tarsi (tarsal sinus) when combined with
  similar depression of the talus

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Talus (Astragalus)

• 2nd largest tarsal bone
• Articulations
• Articulates with four bones
• Tibia and fibula superiorly
• Calcaneus inferiorly
• Navicular anrteriorly

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Navicular (Scaphoid)

• Flattened oval-shaped
• Articulations
• Articulates with four bones
• Talus posteriorly
• Three cuneiforms anteriorly

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Cuneiforms

• Wedge-shaped
• Three bones
• Medial largest
• Intermediate smallest
• Lateral
• Articulations
• Medial cuneiform
• Articulated with four bones navicualr
  proximally 1st and 2nd metatarsals distally
  Intermediate cuneiform laterally
• Intermediate cuneiform
• Articulates with four bones avicular proximally
  2nd metatarsal distally medial and lateral
  cuneiforms on each side
• Lateral cuneiform
• Articulates with six bones navicular proximally
  2nd, 3rd, and 4th metatarsals distally
  intermediate cunefirom medially cuboid laterally

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Cuboid

• Articulations
• Articulates with four bones
• Calcaneus proximally
• Lateral cuneiform and navicular (occasionally)
  medially
• Fourth and fifth metatarsals distally

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Arches

• Two arches to provide a strong, shock-absorbing
  support for body weight
• Longitudinal arch
• Springy
• Composes
• Medial component cal., tal., nav., 1st cun., and
  1st MT
• Lateral component cal., tal., and cub.
• Most of the arch on the medial and midaspects of
  the foot
• Transverse arch
• Located primarily along the plantar surface of
  the distal tarsals and the TMJ
• Composes 1st-3rd cun, and cub.

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Ankle Joint

• Formed by three bones tibia, fibula, and talus
• Frontal view
• The inferior portions of the tibia and fibula
  form a deep socket or thee-sided opening called
  a mortise into which the upper talus fits
• The entire three-part joint space of the ankle
  mortise is not seen in a true AP projection b/c
  of the overlapping of portions of the distal
  fibula and tibia by talus. This caused by the
  more posterior position of the distal fibula
• A 15o internally rotated AP projection, called
  mortise position, is used to visualize this
  mortise joint that should have an even space over
  the entire talar surface
• The distal tibial surface forming the roof of the
  ankle mortise joint is called the tibial plafond
  (ceiling) (potential site of fx)

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Ankle Joint

• Lateral view
• True lateral view shows that the lateral
  malleolus is 1 cm posterior in relationship to
  the medial malleolus

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Ankle Joint

• Axial view

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Exercise
B
A
C
D
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Leg Tibia and Fibula
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Femur (Distal and Mid)

• Anterior view

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Femur (Distal and Mid)

• Posterior view

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Femur (Distal and Mid)

• Lateral view

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Femur (Distal and Mid)

• Axial view

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Patella
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Knee Joint

• Major knee ligaments

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Knee Joint

• Menisci (articular disks)

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Exercise
C
D
A
B
F
E
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Radiographic Positioning

• Positioning considerations
• Radiographic examinations of lower limb below the
  knee are generally done on a tabletop
• Distance 100 cm
• Gonadal shielding
• Use lead vinyl-covered shield
• Shift the unused Bucky tray away from the field
  of x-ray to avoid scattering
• Collimation
• Collimation borders should be visible on all four
  sides if the IR is large enough too allow this
  without cutting off essential anatomy

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Positioning Considerations

• General positioning
• Always place the long axis of the part being
  radiographed // to the long axis of the IR
• If more than on projection is taken on the same
  IR, the part should be // to the long axis of the
  part of the IR being used
• All body parts should be oriented in the same
  direction
• Exception for leg radiograph in adults, the limb
  should be oriented diagonally to include knee and
  ankle joints
• Correct centering
• In general, the par t being radiographed should
  be // to the plane of the IR
• The CR should be 90o or - and should directed to
  the correct centering point (there are exceptions)

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Positioning Considerations

• Exposure factors
• Lower-to-medium kV (50-70)
• Short exposure time
• Small FS
• Adequate mAs for sufficient density
• Optional technique for foot an increase to 70-75
  kV with accompanying decrease in mAs will
  decrease contrast to result in a more uniform
  exposure density b/w the phalanges and the
  tarsals
• Imaging receptors
• Detail screen in used with or without grid
  depending on part thickness

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Positioning Considerations

• Pediatric patients
• Patient motion should be restricted
• Use immobilization device such as sponge, tape,
  or sand bags
• Ask family for help ? ensure protection for help
• Speak to child in a soothing manner and with
  language the child can readily understand to
  ensure maximal cooperation
• Geriatric patients
• Provide clear and complete instructions
• Routine examination might be altered to
  accommodate the older patients physical
  condition
• Use adequate immobilization device
• Exposure factors may need to be reduced

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Positioning Considerations

• Placing of markers and patient ID information
• Always place it in the location least likely to
  superimpose anatomy of interest for that
  projection
• Increase exposure with cast

TYPE OF CAST INCREASE IN EXPOSURE
Small to medium plaster cast Increase mAs 50-60 or 5-7 kV
Large plaster cast Increase mAs 100 or 8-10 kV
Fiberglass cast Increase mAs 25-30 or 3-4 kV
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Positioning Considerations

• Digital imaging considerations
• Collimation insures optimal quality
• 30 rule at least 30 of the IP should be
  exposed to ensure accurate exposure index (or S
  number)
• Lead masking for multiple projections
• Accurate centering as in the FSR
• Grid use with DR acceptable
• Evaluation of exposure index value to verify
  that the exposure factors used were in the
  correct range to ensure an optimum quality image
  with the least possible radiation dose to the
  patient
• Exposure factors
• Wide exposure latitude
• Consider the ALARA principle use highest
  possible kVp with lowest possible mAs
• Generally 60 kVp is the lowest factor used for
  any CR or DR procedures

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Pathologic Indications

• Bone cyst
• Benign neoplastic bone lesion filled with clear
  fluid
• Most often occur near the knee joint in children
  and adolescents
• Generally not detected on radiographs until a
  pathologic fx occurs
• When detected on radiograph they appear as lucent
  areas with a thin cortex and sharp boundaries
• Most common radiographic exam AP lateral of
  affected limb
• Possible radiographic appearance
  well-circumscribed lucency

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Pathologic Indications contd

• Chondromalacia patellae (runners knee)
• Softening of the cartilage under the patella ?
  wearing of cartilage, pain, and tenderness
• Cyclists and runners are vulnerable to this
  condition
• Most common radiographic exam AP lateral knee,
  tangential (axial) of femoropatellar joint
• Possible radiographic appearance pathology of
  femoropatellar joint space, possible misalignment
  of patella

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Pathologic Indications contd

• Chondrosarcomas
• Most common radiographic exam AP lateral of
  affected limb, CT, MRI
• Possible radiographic appearance bone
  destruction with calcification in the
  cartilaginous tumor
•  
• Encondromas
• Most common radiographic exam AP lateral of
  affected limb
• Possible radiographic appearance well-defined
  radiolucent tumor with thin cortex (often result
  in pathologic fx with minimal trauma)
• Ewings sarcoma
• Most common radiographic exam AP lateral of
  affected limb, CT, MRI
• Possible radiographic appearance ill-defined are
  of bone destruction with surrounding onion peel
  (layers of periosteal reaction)
• Exostosis (osteochondroma)
• Most common radiographic exam AP lateral of
  affected limb
• Possible radiographic appearance a projection of
  bone with cartilaginous cap grows // to shaft
  and away from nearest joint
• Fractures

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Pathologic Indications contd

• Gout
• Form of arthritis that my be hereditary
• Uric acid appears in excessive quantities in the
  blood and may be deposited in the joints and
  other tissues
• Common initial attacks occur in the 1st MTPJ of
  the foot
• Later attacks may also occur in other joints such
  as the 1st MCPJ of the hand, but generally these
  are not seen radiographically until more advanced
  conditions develop
• Most cases occur in men, and first attacks rarely
  occur before age 30
• Most common radiographic exam AP (obl.)
  lateral of affected part (most common initially
  in MTPJ of foot)
• Possible radiographic appearance uric acid
  deposits in joint space destruction of joint
  space

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Pathologic Indications contd

• Joint effusion
•  
• Multiple myeloma
• Most common radiographic exam AP lateral of
  affected part
• Possible radiographic appearance multiple
  punched-out osteolyte lesions throughout
  affected bone
• Osgood Schlatter disease
• Inflammation of the bone and cartilage involving
  the anterior proximal tibia
• Most common in boys ages 10-15
• Cause an injury that occurs when the large
  patellar tendon detaches part of the tibial
  tuberosity to which it is attached
• Most common radiographic exam AP lateral knee
• Possible radiographic appearance fragmentation
  and/or detachment of tibial tuberosity by
  patellar tendon

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Pathologic Indications contd

• Osteoarthritis
• Most common radiographic exam AP, obl. lateral
  of affected part
• Possible radiographic appearance narrowed,
  irregular joint spaces with sclerotic articular
  surfaces and spurs
• Exposure factor adjustment advanced stage may
  require slight decrease (-)
• Osteoclastomas (giant cell tumors)
• Benign bone lesions
• Occur in long bones of young adults
• Usually occur in the proximal tibia or distal
  femur after epiphyseal closure
• Most common radiographic exam AP lateral of
  affected part, CT, MRI
• Possible radiographic appearance large bubbles
  separated by thin stripes of bone

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Pathologic Indications contd

• Osteogenic sarcomas (osteosracomas)
• Most common radiographic exam AP lateral of
  affected part, CT, MRI
• Possible radiographic appearance excessively
  destructive lesion with irregular periosteal
  reaction classic appearance is sunburst pattern
  that is diffuse periosteal reaction
• Osteoid osteomas
• Benign bone lesions
• Usually occurs in teenagers or young adults
• Symptoms include localized pain that typically
  worsens at knight but is relieved by
  over-the-counter anti-inflammatory or pain
  medications
• The tibia and the femur are the most likely sites
  of these lesions
• Most common radiographic exam AP lateral of
  affected part
• Possible radiographic appearance small,
  round-oval density with lucent center

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Pathologic Indications contd

• Osteomalacia (rickets)
• Means bone softening
• Caused by lack of bone mineralization b/c of the
  deficiency in calcium, phosphorous, and/or vit. D
  in the diet or an inability to absorb these
  minerals
• Bowing of the weight-bearing parts often results
• In children, this defect is known as rickets and
  more commonly results in bowing of the tibia
• Most common radiographic exam AP lateral of
  affected limb
• Possible radiographic appearance decreased bone
  density, bowing deformity in weight-bearing limbs
• Exposure factor adjustment loss of bone matrix
  requires decrease (-)
• Pagets disease (osteitis deformas)
• Most common radiographic exam AP lateral of
  affected part/s
• Possible radiographic appearance mixed areas of
  sclerotic and cortical thickening and lytic or
  radiolucent lesions, cotton wool appearance
• Exposure factor adjustment excessive sclerotic
  areas may require increase ()

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Pathologic Indications contd

• Reiter syndrome
• Affects the sacroiliac joint and lower limbs of
  the young men
• Includes bilateral attack, arthritis, urithritis,
  and conjunctivitis
• Caused by a previous infection of the GIT, such
  as salmonella, or by a sexually transmitted
  infection
• Most common radiographic exam AP lateral of
  affected part
• Radiographic appearance specific area of bony
  erosion at the Achilles tendon insertion on the
  posterosupoerior margins of the calcaneus