SI Joints

Question 1

Why are both SI joints imaged?

Answer 1

For comparison

Question 2

What AEC cell is used for SI joints?

Answer 2

Centre

Question 3

What are the essential projections for SI joints?

Answer 3

AP/PA axial
AP oblique (RPO,LPO)

Question 4

What is the angulation for AP axial SI joints if the patient is in a supine position?

Answer 4

30-35 degrees cephalad
*30 for males
*35 for females

Enters MSP 2” below ASIS level

Question 5

Why is the angulation increased for females in supine position?

Answer 5

Increased lumbosacral curve

Question 6

What is the angulation for PA axial SI joints if the patient is prone?

Answer 6

30-35 degrees caudad

Enters MSP at level L4 or slightly above iliac crest

Question 7

T/F
In an AP axial SI joint projection, the sacrum will be elongated with the SP superimposed over the inferior sacral segments

Answer 7

True

Question 8

Why is angulation used to for SI joint projections?

Answer 8

To demonstrate the SI joints without foreshortening

Question 9

T/F
Patients with less or greater lumbosacral curvature will require a decrease or increase respectively in cephalic angulation

Answer 9

True

Question 10

The SI joints and the 1st through 3rd sacral segments are foreshortened

Answer 10

If an AP axial SI joint projection is taken with a perpendicular CR or without enough cephalad angulation

Question 11

The sacrum and Sl joints demonstrate elongation and the stmphysis pubis is superimposed over the inferior aspects of the sacrum and SI joints

Answer 11

If the AP axial Sl joint projection is taken with too much cephalic angulation
*pubic symphysis is superimposed on SI joints

Question 12

For an AP oblique projection of the SI joints, how much rotation is used, and what side is elevated?

Answer 12

25-30 degree posterior oblique position
Side of interest elevated

Question 13

Where does the CR enter for an AP oblique SI joint projection?

Answer 13

1” medial to elevated ASIS

Question 14

T/F
An AP oblique SI projection taken with the patient in RPO demonstrates the left SI joint

Answer 14

True

Question 15

The inferior and superior sacral aspects of the ala are demonstrated without ilium superimposition, whereas the lateral sacral ala is superimposed over the iliac tuberosity

Answer 15

AP oblique SI joint

Insufficient rotation
*see textbook

Question 16

The ilium is superimposed over the lateral sacral ala and the inferior sacrum

Answer 16

AP oblique SI joints

Excessive rotation