Pelvis & Hip Technique

Question 1

Indications for x-raying - 5 points

Answer 1

?# stable - avulsion #, pubic rami #, sacral #
?# unstable - compression #, open book #, complex #, acetabular #
?# NOF - intracapsular, extracapsular
? anterior or ? posterior dislocation
Paediatrics - DDH, Legg-Calve-Perthes Disease, Slipped epiphysis

Question 2

How are the hip bones united

Answer 2

anteriorly by symphysis pubis

posteriorly at sacrum through sacro-iliac joints

Question 3

What are 4 differences between the female and male pelvis

Answer 3

Sub-pubic angle - FEMALES wide MALES narrow
Pelvic Inlet - FEMALES oval/rounded MALES heart-shaped
Obturator Foramen - FEMALES oval MALES round
Acetabulum - FEMALES small MALES large

Question 4

How is the patient positioned for an AP Pelvis examination

Answer 4

patient supine aligned with image receptor, arms on chest, long axis of patient co-incident with midline of table, ASIS equidistant from tabletop, MSP of patient at 90’ to tabletop, internally rotate legs from true AP position to minimise foreshortening of femoral neck

Question 5

where to centre for an AP pelvis examination

Answer 5

midway between level of ASIS and superior border of symph pubis

Question 6

When do you expose for an AP pelvis examination

Answer 6

on arrested respiration at 100cm SID

Question 7

Image criteria for an AP pelvis examination (5 points)

Answer 7

superior border of iliac crests and L4/5 and proximal 1/3 of femur inferiorly
midline of patient centralised
spinous processes of vertebral bodies seen in midline therefore showing no rotation
iliac bones are equal size therefore no rotation
obturator foramen is equal size/shape therefore no rotation

Question 8

What is Shenton’s Line

Answer 8

an imaginary line drawn along the inferior border of the superior pubic ramus (superior border of the obturator foramen) and along the infero-medial border of NOF - should be continuous and smooth

Question 9

how is the patient positioned for an AP single hip

Answer 9

affected hip aligned with image receptor

Question 10

where to centre for an AP single hip

Answer 10

2.5cm along the bisector of the line joining ASIS and symph pubis

Question 11

what do you collimate for an AP single hip

Answer 11

superior distal portion of iliac bone and medially symph pubis

Question 12

Image criteria for an AP single hip

Answer 12

obturator foramen appears open
NOF not foreshortened
greater trochanter, femoral neck and head in profile
lesser trochanter not fully projected beyond medial border of femur

Question 13

how is the patient positioned for a lateral oblique hip

Answer 13

patient abducts, flexes and externally rotates affected leg through 45’ towards affected side, affected hip aligned to centre of x-ray table, support knee to aid comfort and posteriorly to aid stability

Question 14

where to centre for a lateral oblique hip

Answer 14

crease of groin/femoral pulse

Question 15

Image criteria for a lateral oblique hip

Answer 15

lateral portion of pubic rami and ischium of affected side
femoral neck seen in profile, superimposed by greater trochanter
obturator foramen (if seen) reduced in size as ischium and pubic rami become superimposed

Question 16

Where to position patient for a horizontal beam lateral hip

Answer 16

grid image receptor replaced at 45’ angle to patient with longitudinal axis parallel to neck of femur, upper border in contact with soft tissues above level of iliac crest, radiolucent pad used to support receptor in vertical position or patient asked to assist, unaffected leg raised, flexed at knee and ankle supported

Question 17

where to central for a horizontal beam lateral hip

Answer 17

horizontal central ray directed at 90’ to crease of groin

Question 18

where to collimate for a horizontal beam lateral hip

Answer 18

anterior and posterior soft tissue borders

Question 19

Image criteria for a horizontal beam lateral hip

Answer 19

hip joint co-incident with midline
no foreshortening of NOF due to no external rotation of femur over NOF
greater trochanter seen in profile because not superimposed
ischial tuberosity projected posteriorly to patient