WK 2 Pelvis, hip and femur

Pelvis and Hip

Pelvis

Bones

  • 3 bones make up the pelvis: ilium, ischium and pubic - all fuse

  • Acetabulum formed by the fusion of the 3 bones - deep articular surface and obturator foramen lays inferior to it

  • Joints: sacroiliac joint and pubic symphysis

Pelvic cavities

  • Pelvic brim: horizontal plane that passes from the sacral promontory to the upper margin of the pubic symphysis

  • Greater pelvis (false): holds abdominal organs

  • Lesser pelvis (true): holds pelvic organs

  • Pelvic inlet: superior circumference of the true pelvis and pelvic brim (has specific views as it is curved)

  • Pelvic outlet: inferior circumference of the true pelvis formed by the pubic arch

    • Boundaries:

    • Anterior: rami of ischium and pubis and lower margin of symphysis pubis

    • Posterior: coccyx

    • Lateral; ischial spines and ischial tuberosities

Gender differences in the pelvis

Radiography of the pelvis

Clinical indications

Trauma

  • Dislocation of the hip - tendons an ligaments spasming and pinching - painful

  • Pubic symphysis dislocation

  • Intertrochanteric fracture: fracture between greater and lesser trochanters

Projections:

  • Standard: AP - normally comes with hip referral too

  • Modified: AP charnley - includes more of femoral shaft - for prosthetic devices and total hip replacements

  • Additional views

    • Oblique: for the ilium

    • Judet: obliques for the acetabulum

    • AP axial inlet and outlet views: for pubic rami, ischium and pubic symphysis

Parameters for all pelvic views

  • Use grid

  • Broad focus

  • SID: 100cm

  • kVp: 75-85

  • mAs: 15-40 - average patient is 25

  • AEC: 2 lateral chambers

  • Breathing: suspended respiration

  • Gonadal shielding for females - dependent on clinical indications eg. 35 yr old female follow up x-ray

  • Greater trochanter is in the same line as the pubic symphysis

Positioning

AP pelvis:

  • ASIS equidistant from the IR

  • Internal rotation of legs 15-20 degrees

  • CR - 5cm above pubic symphysis or midway between ASIS and pubic symphysis

  • Collimate to include iliac crests and pubic symphysis with greater troch

Assessment criteria:

  • iliac crest levels the same - tilt

  • Shape of ilium equal on both sides - if one is wider it is rotated towards that side

  • Obturator foramen size equal - side that is narrower is the direction of rotation

  • Sacrum and coccyx midline with pubic symphysis - if rotated to one side the pelvis is rotated in the opposite direction (sacrum and coccyx visualised towards the left = right rotation)

  • Internal rotation of the femur so the GT is in profile and LT is superimposed

  • Trabecular bony patterns

AP Charnley:

  • Align ASIS to upper collimation field - captures full length of prosthetic device

  • Same assessment criteria

Judet method: right or left acetabulum - two views of the same side

  • Projection 1: unaffected side raised 45 degrees, collimate to affected acetabulum and CR 5cm distal and medial from ASIS

  • Projection 2: affected side raised 45 degrees, collimate to affected acetabulum and CR 5cm distal and medial from ASIS

AP Axial inlet:

  • Patient supine AP position

  • Tube angled 40 degrees caudally

  • CR midway between ASIS

  • If patient is unable to be fully supine - increase angle to open up pelvic inlet

AP Axial outlet:

  • Patient supine AP position

  • Tube angled 20-35 degrees (males) and 30-45 degrees (females) cranially

  • CR at level of greater troch - midline

AP axial inlet and outlet views can help with pubic ramus fractures

Hip/Proximal femur

  • femoral neck fracture common

  • Angle of inclination - angle of head of femur to the femoral shaft - 110-140 degrees

  • Angle of inclination changes with age and length of femur

  • Hip in anatomical position: GT and LT in profile and femoral neck is foreshortened

    • To counteract: internal rotation 15-20 degrees - elongate NOF and LT superimposed with shaft

Radiography of the hip

Clinical indications

  • Same of pelvis

  • Surgical assessment (pre-op, templating and mag-marker) eg. THR

  • Osteoarthritis

Projections

Standard

  • AP unilateral/bilateral hips (AP pelvis/charnley)

  • Lateral hip:

    • Medio-lateral obliques (unilateral): Rotating hip from medial to lateral side - projection is lateral, position is oblique hip - rotating hip not body

    • Frog leg bilateral - paediatric

    • Axiolateral horibeam

    • Clements- Nakayama - when unable to move patients

Parameters for AP Hip and Lateral

  • Use grid

  • Broad focus

  • SID: 100cm

  • kVp: 75-85

  • mAs: 25-50 - average patient is 25

  • AEC: middle chamber

Parameters for Axiolateral hip/Clements-Nakayama (Horibeam will wall bucky or free detector)

  • Use grid

  • Broad focus

  • SID: 100cm

  • kVp: 80-100

  • mAs: 80-100 - average patient is 80 (use less if it is free detector)

  • AEC: middle chamber

Patient prep

  • try to do in bed if possible

  • do not forcefully internally rotate - cut femoral artery = no supply to lower limb

  • NOF presents as foreshortened leg and externally rotated

Positioning

AP hip unilateral:

  • Supine

  • CR over femoral neck - CR at greater troch or at the level of PB upper margin

  • Internally rotate

Mediolateral hip:

  • Flex knee to rotate affected leg 45 degrees so the foot is touching the other knee

  • CR at femoral neck

  • NOF partially superimposed with GT

  • Good visualisation of hip joint, acetabulum and head of femur

  • OR rotation of the pelvis to 60-75 degrees with femur abducted - NOF foreshortened but can see head an acetabulum

Frog leg lateral - bilateral

  • Flex hips and knees so that soles of feet touching

  • Paediatric

Axiolateral hip

  • in trauma

  • unaffected limb raised so beam can shoot through femoral neck - crease

  • IR parallel to femoral neck

Clements-nakayama

  • when patient cannot move either leg

  • on very edge of bed with IR lowered down - try not to shoot through bed

  • Caudal angle of 15-20 degrees from horizontal position

  • CR at NOF

Dunns

Radiography of the femur

  • Clinical indications same as pelvis and hip

  • Patient care for trauma - limited movement

Projections

Standard

  • AP proximal (same has hip) and distal (same as knee) femur to include prosthetic device and both hip joint and knee joint

  • Lateral femur

    • Medio-lateral obliques - similar to hip

    • Lateral distal - similar to knee - CR over the knee joint

    • Axiolateral - horibeam proximal and distal (cr over knee joint)

Parameters

  • use grid

  • Broad focus

  • 100cm SID

  • kVp: 70-80 (if out of bucky for distal femur use knee exposures - 60-70)

  • mAs: 25-40 or 50-100 (horibeam or large patient)

  • AEC middle chamber

Positioning

AP femur proximal and distal:

  • supine

  • leg internally rotated

  • CR mid femur with ASIS upper border of collimation (proximal) OR CR lower third of femur with knee joint included (distal)

Lateral femur (proximal):

  • abduct 60 degrees - move body to achieve lateral femur

  • Mediolateral hip to include shaft of femur

  • OR axiolateral HB of hip to include shaft of femur (trauma)

Lateral femur (distal):

  • Mediolateral - body to the side and CR at knee joint

  • OR axiolateral HB to include shaft and knee joint