Lower Extremities

• Radiographic examinations of lower extremities

  • Foot
  • Ankle
  • Tibia Fibula
  • Knee
  • Femur

  
• Content


  • Basic Radiographic Examination
  • Foot (AP & AP Oblique)
  • Ankle (AP & Lateral)
  • Tibia Fibula (AP & Lateral)
  • Knee (PA & Lateral)
  • Femur (AP & Lateral)

  
• Foot AP Projection


  Clinical indication: Location and extent of fractures and fragment alignments, joint space abnormalities, soft tissue effusions, location of opaque foreign bodies

  
• Foot AP Projection


  • Minimum SID— (100 cm)
  • IR size—24 × 30 cm (10 × 12 inches), lengthwise
  • Nongrid
  • Analog—60 ± 5 kV range; alternatively, 70 to 75 kV and reduced mAs for increased exposure latitude for more uniform density (brightness) of phalanges and tarsals
  • Digital systems—60 to 70 kV range
  • mAs range in 3 to 5 mAs

  
• Foot AP Projection


  Shielding: Shield radiosensitive tissues outside region of interest
• Foot AP Projection


  1. Patient Positioning: The patient is seated on the X-ray table, supported if necessary, with the affected hip and knee flexed. The plantar aspect of the affected foot is placed on the cassette and the lower leg is supported in the vertical position by the other knee.

  2. Alternatively, the cassette can be raised on a 15-degrees foam pad for ease of positioning.

  
• Foot AP Projection


  Part Position: Extend (plantar flex) foot but maintain plantar surface resting flat and firmly on IR. Align and center long axis of foot to CR and to long axis of portion of IR being exposed. Use sandbags if necessary to prevent IR from slipping on tabletop. If immobilization is needed, flex opposite knee also and rest against affected knee for support.

  
• Foot AP Projection


  Central Ray: Angle CR 10° posteriorly (toward heel) with CR perpendicular to metatarsals. Direct CR to base of third metatarsal.

  
• Detecting Rotation


  Any rotation will cause Medial and Intermediate Cuneiform joint space to be closed. Evaluate position of navicular tuberosity and superimposition of talar with calcaneum.
• AP Oblique Projection—Medial Rotation: Foot

  Clinical Indication: Location and extent of fractures and fragment alignments, joint space abnormalities, soft tissue effusions, location of opaque foreign bodies

  
• AP Oblique Projection—Medial Rotation: Foot

  • Minimum SID— (100 cm)
  • IR size—24 × 30 cm (10 × 12 inches), lengthwise
  • Nongrid
  • Detail screens for analog imaging
  • Analog—60 ± 5 kV range; alternatively, 70 to 75 kV and reduced mAs for increased exposure latitude for more uniform density of phalanges and tarsals
  • Digital systems—60 to 70 kV range
• AP Oblique Projection—Medial Rotation: Foot

  Shielding: Shield radiosensitive tissues outside region of interest
• AP Oblique Projection—Medial Rotation: Foot

  Patient Position: Place patient supine or sitting; flex knee, with plantar surface of foot on table; turn body slightly away from side in question.

  
• AP Oblique Projection—Medial Rotation: Foot


  Part Position: Align and center long axis of foot to CR and to long axis of portion of IR being exposed. Rotate foot medially to place plantar surface 30° to 40° to plane of IR. The general plane of the dorsum of the foot should be parallel to IR and perpendicular to CR. Use 45° radiolucent support block to prevent motion. Use sandbags if necessary to prevent IR from slipping on tabletop.

  
• AP Oblique Projection—Medial Rotation: Foot

  Central Ray: CR perpendicular to IR, directed to base of third metatarsal.
• Ankle AP View


  Clinical Indications: Bony lesions or diseases involving the ankle joint, distal tibia fibula, proximal talus and proximal fifth metatarsal.
• Ankle AP View


  • Minimum SID— (100 cm)
  • IR size—24 × 30 cm (10 × 12 inches), lengthwise
  • Nongrid
  • Detail screens for analog imaging
  • Analog—60 ± 5 kV range
  • Digital systems—60 to 70 kV range
• Ankle AP View


  Shielding: Shield radiosensitive tissues outside region of interest
• Ankle AP View


  Patient Position: Place patient in the supine position; place pillow under patient's head; legs should be fully extended.
• Ankle AP View


  Part Position: Center and align ankle joint to CR and to long axis of portion of IR being exposed. Do not force dorsiflexion of the foot; allow it to remain in its natural position. Adjust the foot and ankle for a true AP projection. Ensure that the entire lower leg is not rotated. The intermalleolar line should not be parallel to IR.

  
• Ankle AP View


  Central Ray: CR perpendicular to IR, directed to a point midway between malleoli
• Lateral Ankle


  Clinical indication: Projection is useful in the evaluation of fractures, dislocations, and joint effusions associated with other joint pathologies.
• Lateral Ankle


  • Minimum SID— (100 cm)
  • IR size—24 × 30 cm (10 × 12 inches), lengthwise
  • Nongrid
  • Detail screens for analog imaging
  • Analog—60 ± 5 kV range
  • Digital systems—60 to 70 kV range
• Lateral Ankle


  Shielding: Shield radiosensitive tissues outside region of interest
• Lateral Ankle


  Patient Position: Place patient in the lateral recumbent position, affected side down; provide a pillow for patient's head; flex knee of affected limb about 45°; place opposite leg behind injured limb to prevent over-rotation.
• Lateral Ankle


  Part Position: Center and align ankle joint to CR and to long axis of portion of IR being exposed. Place support under knee as needed to place leg and foot in true lateral position. Dorsiflex foot so that plantar surface is at a right angle to leg or as far as patient can tolerate; do not force.

  
• Lateral Ankle


  Central Ray: CR perpendicular to IR, directed to medial malleolus.
• AP Tibia Fibula (Leg)

  Clinical Indication: Pathologies involving fractures, foreign bodies, or lesions of the bone
• AP Tibia Fibula (Leg)

  • Minimum SID—40 inches (102 cm); may increase to 44 to 48 inches (112 to 123 cm) to reduce divergence of x-ray beam and to include more of body part
  • IR size—35 × 43 cm (14 × 17 inches), lengthwise (or diagonal, which requires 44 inches [112 cm] minimum SID)
  • Nongrid (unless lower leg measures >10 cm)
  • Analog—70 ± 5 kV range
  • Digital systems—70 to 80 kV range
  • To make best use of anode heel effect, place knee at cathode end of x-ray beam

  
• AP Tibia Fibula (Leg)

  Shielding: Shield radiosensitive tissues outside region of interest
• AP Tibia Fibula (Leg)


  Patient position: Place patient in the supine position; provide a pillow for patient's head; leg should be fully extended.
• AP Tibia Fibula (Leg)

  Part position: Adjust pelvis, knee, and leg into true AP with no rotation. Place sandbag against foot if needed for stabilization, and dorsiflex foot to 90° to leg if possible. Ensure that both ankle and knee joints are 1 to 2 inches (3 to 5 cm) from ends of IR (so that divergent rays do not project either joint off IR). If limb is too long, place the leg diagonally (corner to corner) on one 35 × 43 cm (14 × 17 inches) IR to ensure that both joints are included. (Also, if needed, a second smaller IR may be taken of the joint nearest the injury site.)

  
• AP Tibia Fibula (Leg)

  Central Ray: CR perpendicular to IR, directed to midpoint of leg
• Lateral Tibia Fibula


  Clinical indication: Localization of lesions and foreign bodies, Alignment of fractures demonstrated
• Lateral Tibia Fibula


  • Minimum SID—40 inches (102 cm); may increase to 44 to 48 inches (112 to 123 cm) to reduce divergence of x-ray beam and to include more of body part
  • IR size—35 × 43 cm (14 × 17 inches), lengthwise (or diagonal, which requires 44 inches [112 cm] minimum SID)
  • Nongrid (unless lower leg measures >10 cm)
  • Analog—70 ± 5 kV range
  • Digital systems—70 to 80 kV range
• Lateral Tibia Fibula


  Shielding: Shield radiosensitive tissues outside region of interest
• Demonstration of femoral and tibial condyles in profile

  • Intercondylar eminence centered within intercondylar fossa
  • Some overlap of the fibula and tibia is visible at both proximal and distal ends
• Collimation


  To the area of interest
• Exposure


  • Correct use of anode heel effect results in an image with nearer equal density at both ends of IR
  • No motion is present, as evidenced by sharp cortical margins and trabecular patterns
  • Contrast and density (brightness) should be optimum to visualize soft tissue and bony trabecular markings at both ends of tibia
• Clinical indication


  • Localization of lesions and foreign bodies
  • Alignment of fractures demonstrated