Pelvis and hip

• Pelvis is the part of the trunk inferioposterior (below-behind) to the abdomen in the transition area between the trunk and the lower limbs

  
• Male vs female pelvis

  
• Pelvis inlet


  Anteriorly by the pubic crest (or pubic symphysis), posteriorly by the anterior margin of the base of the sacrum (or the ala of sacrum) and sacrovertebral angle (or sacral promontory), laterally by the pectineal line (or iliopectineal line) and arcuate lines

  
• Pelvis outlet


  Behind by the point of the coccyx, laterally by the ischial tuberosities

  
• Shenton's line


  An imaginary line drawn along the inferior border of the superior pubic ramus (superior border of the obturator foramen and along the inferomedial border of the neck of femur). This line should be continuous and smooth.

  
• Interruption of Shenton's line


  Can indicate (in the correct clinical scenario) developmental dysplasia of the hip (DDH) or fractured neck of femur

  
• Clinical indications


  • Ankylosing spondylitis (AS)
  • Congenital Hip Dysplasia
  • Dislocation
  • Fracture
  • Metastasis
  • Osteoarthritis / Degenerative joint disease
  • Osteoporosis
  • Tumor

  
• Radiation protection


  • Gonadal shield – if appropriate
  • Proper collimation
• Radiographic projections of pelvis

  • AP (Anteroposterior)
  • Frog Leg View
  • Outlet Projection
  • Inlet Projection
  • Sacroiliac Joints Projection

  
• Antero-posterior projection


  1. Position of patient: Supine

  2. Position of part: Center the midsagittal plane of the body to the midline of the grid, adjust in a true supine position

  3. Medially rotate the feet and lower limbs about 15° to 20° to place the femoral necks parallel with the plane of IR (unless contraindicated)

  4. The heels should be placed about 20-24cm apart

  5. Immobilize

  6. No rotation: both ASIS to the tabletop are equidistant

  7. Center the IR midway between the ASIS and the pubic symphysis (5cm inferior to level of ASIS - average size)

  8. Central ray: perpendicular to the midpoint of the IR

  
• AP bilateral frog-leg projection

  1. Patient Positioning: Supine, patient at midline of table/IR and to CR, ASIS equidistant to tabletop, center IR to CR (at level of femoral heads, upper border IR = level of Iliac crest), flex both knees = 90°, place the plantar surfaces of feet together, abduct both femurs (40°-45° from vertical), support/immobilize

  2. Central Ray: perpendicular to IR, 7.5cm below level of ASIS/ 2.5cm above SP

  3. Collimation: collimate to IR borders on four sides

  
• AP axial "outlet" projection – Taylor Method (for Anterior/Inferior Pelvic Bones)

  1. Patient Positioning: Supine, legs extended, support under knees, patient at midline of table/IR and to CR, no rotation of pelvis

  2. Center IR to projected CR

  3. Central ray: angled to cephalad 20°-35° (males)/ 30-45°(females), 3 – 5cm distal to the superior border of the SP/greater trochanter

  4. Collimate closely on four sides to area of interest

  
• AP axial "inlet" Projection - Bridgeman Method

  1. Patient Positioning: Supine, legs extended, support under knees, patient at midline of table/IR and to CR, no rotation of pelvis

  2. Center IR to projected CR

  3. CR: caudad 40° (near perpendicular to plane of inlet) to a midline point at level of ASIS

  4. Collimation 4 sides to ROI
• Clinical indications for radiographic projections of the hip joint

  • Osteoarthritis
  • Fracture
  • Dislocation
  • Hip Replacement
  • Avascular necrosis

  
• Patients with neck of femur fractures


  • Present with a history of falling over
  • One leg shortened and externally rotated
  • Patients are usually old

  
• Basic radiographic projections (non-trauma protocol)

  • AP Projection
  • Unilateral "frog-leg" Projection

  
• Additional radiographic projection (trauma protocol)

  • Axiolateral Inferosuperior Projection: Horizontal Beam
• Technical factors


  • IR size 24 x 30 cm (10 x 12 inches), lengthwise
  • Moving or stationary grid
  • 80 ± 5 kVp range
  • FFD 100 cm
  • Place shielding over gonads and pelvic area, ensuring that affected hip is not obscured

  
• Patient position for AP projection

  Patient supine on the table, arms at side or across upper chest
• Part position for AP projection

  1. Ensure no rotation of pelvis (ASIS equidistance to table)

  2. Rotate affected leg internally 15° to 20° (do not attempt for internally rotation if fracture or dislocation suspected)

  
• Central ray for AP projection

  CR is perpendicular to IR, directed 1 or 2 inches (2.5 to 5 cm) distal to midfemoral neck (to include all of orthopedic appliance of hip if present)

  
• Collimation for AP projection

  Collimate closely on 4 sides
• Radiographic criteria for AP projection

  • The proximal 1/3 of the femur should be visualized, along with the acetabulum and adjacent parts of pubis, ischium, and ilium
  • Any existing orthopedic appliance should be visible
  • The greater trochanter, femoral head, and neck should be in full profile without foreshortening
  • The lesser trochanter should not project beyond the medial border of the femur
  • Collimated field should demonstrate the entire hip joint and any orthopedic appliance
  • The femoral neck in the center of the collimation area
  • Optimal exposures visualize the margins of the femoral head and acetabulum through overlying pelvic structures
  • Trabecular markings of greater trochanter and femoral neck appear sharp

  
• Patient position for Frog-Leg projection


  Patient supine on the table, arms at side or across upper chest

  
• Part position for Frog-Leg projection

  1. Flex knee and hip on affected side, with sole of foot against inside of opposite leg, near knee if possible

  2. Abduct femur 45° from vertical for general proximal femur region

  3. Place support sponge under hip and knee of raised side

  
• Central ray for Frog-Leg projection

  CR directed to affected midfemoral neck (femoral neck is 3- 4 inches distal to ASIS)

  
• Collimation for Frog-Leg projection

  Collimate closely on 4 sides

  
• Radiographic criteria for Frog-Leg projection

  • Lateral views of acetabulum and femoral head and neck, trochanteric area, and proximal 1/3 of femur are visible
  • Proper abduction of femur is demonstrated by femoral neck seen in profile, superimposed by greater trochanter
  • Proper centering is evidenced by femoral neck in center of collimated field
  • Optimal exposure visualizes the margins of the femoral head and the acetabulum through overlying pelvic structures without overexposing other parts of the proximal femur
  • Trabecular markings and bony margins of proximal femur and pelvis should appear sharp

  
• Patient position for Axiolateral projection


  Patient supine on the table, arms at side or across upper chest
• Part position for Axiolateral projection

  1. Flex and elevate unaffected leg, provide support

  2. Place IR in crease above iliac crest and adjust so that is parallel to femoral neck and perpendicular to CR (use cassette holder)

  3. Internally rotate affected leg 15° to 20° unless contraindicated by possible fracture or pathology

  
• Central ray for Axiolateral projection


  CR directed perpendicular to femoral neck and to IR

  
• Collimation for Axiolateral projection

  Collimate closely on 4 sides
• Radiographic criteria for Axiolateral projection

  • Lateral oblique view of acetabulum, femoral head and neck, and trochanteric area are visible
  • Femoral head and neck seen in profile, with only minimal superimposition by greater trochanter
  • Lesser trochanter is seen projecting posterior to femoral shaft
  • Femoral neck and trochanters should be centered to center of IR
  • Collimation field should include from acetabulum to proximal femur, including both trochanters
  • Optimal exposure visualizes femoral head and neck without overexposing proximal femoral shaft
  • Bony margins and trabecular markings should be visible and sharp

  
• Anatomical structures shown in radiographic projections

  • Femoral head
  • Acetabulum
  • Ischial tuberosity
  • Femoral neck
  • Greater trochanter
  • Lesser trochanter

  
• The importance of a true AP hip position

  • With the patient's legs externally rotated, the greater trochanter is partially superimposed over the femoral neck
  • With the patient's legs internally rotated, there is maximum visualisation of the femoral neck
  • Internal rotation of the patient's leg can be over-done, causing the lesser trochanter to not be demonstrated

  
• Shenton's Line
• DBP 30103 Imaging Technique I
• Clinical indications for radiographic projections of the hip joint

  • Osteoarthritis
  • Fracture
  • Dislocation
  • Hip Replacement
  • Avascular necrosis

  
• Patients with neck of femur fractures


  • Present with a history of falling over
  • One leg shortened and externally rotated
  • Patients are usually old

  
• Basic radiographic projections (non-trauma protocol)

  • AP Projection
  • Unilateral "frog-leg" Projection