SI joints/ sacrum and coccyx positioning quiz

Position of patient for the AP oblique (RPO/LPO) SI joints

patient is in supine position and the head is elevated on a firm pillow

Position of part for AP oblique (RPO/LPO) SI joints

• elevate side of interest approx 25 to 30 degrees and support the shoulder, lower thorax and upper thigh

• Side being examined is the farther from the IR. Use the LPO position to show right joint and the RPO position to show left joint

• Adjust patients body so that its long axis is parallel with long axis of the table

• Align body so that a Sagittal plane passing 1 inch medial to the ASIS of the elevated side is centered to the midline of the table

• Check rotation at several points along the back

• Center IR at level of the ASIS

Respiration for AP oblique (RPO/LPO) SI joints

Suspend

Central ray for AP oblique (RPO/LPO) SI joints

Perpendicular to the center of the IR entering 1 inch medial to the elevated ASIS

Collimation for AP oblique (RPO/LPO) SI joints

6×10

Structures shown for AP oblique (RPO/LPO) SI joints

Sacroiliac joint farthest from IR and an oblique projection of adjacent structures. Both sides examined for comparison

Evaluation criteria for AP oblique (RPO/LPO) SI joints

• evidence of collimation

• Side marker

• Open sacroiliac joint space farthest from IR with minimal overlapping of the ilium and sacrum

• Joint centered on radiograph

Central ray for AP Axial oblique (RPO/LPO) SI joints

20 to 25 degrees cephalad entering 1 inch medial and 1 ½ inches distal to the elevated ASIS

What’s wrong with #41 AP axial oblique of the right SI joint

• centered too medial

• No lead letter

• Too obliqued/ rotated

• Not collimated

what’s wrong with # 39 AP axial oblique of the left SI joint

• centered too superior

• SI joint not opened

• Too rotated

• Tube/ Bucky not aligned

• Not marked correctly/ marker is placed side down instead of up

• Not collimated

What’s wrong with #40 AP axial oblique of the left SI joint

• not obliqued enough

• Centered too medial

• not collimated

• Marked side down instead of up

Position of patient for PA oblique (RAO/LAO) SI joints

• patient prone

• Place small firm pillow under the head

Position of part for PA oblique (RAO/LAO) SI joints

• adjust patient by rotating side of interest toward table until body rotation of 25 to 30 degrees is achieved. Have patient rest on forearm and flexed knee of elevated side

• Side being examined should be closer to the IR. Use the RAO position to show right joint and LAO position to show left joint

• Check degree of rotation at several points along anterior surface of the patients body

• Adjust patients body so that it’s long axis is parallel with the long axis of the table

• Center body so that a point 1 inch medial to the ASIS closest to the IR is centered to the grid

• Center IR at level of ASIS

Respiration for PA oblique (RAO/LAO) SI joints

Suspend

Central ray for PA oblique (RAO/LAO) SI joints

Perpendicular to the IR and centered 1 inch medial to the ASIS closer to the IR

Collimation for PA oblique (RAO/LAO) SI joints

6×10

Structures shown for PA oblique (RAO/LAO) SI joints

SI joint closest to the IR

Evaluation criteria for PA oblique (RAO/LAO) SI joints

• proper collimation

• Side marker

• Open sacroiliac joint space closest to the IR or minimal overlapping of the ilium and sacrum

• Joint centered on radiograph

Central ray for PA axial oblique (RAO/LAO) SI joints

20 to 25 degrees caudad to enter the patient at the level of the transverse plane, passing 1 ½ inches distal to the L5 spinous process and exit at the level of the ASIS

What should be done before examination of the AP/PA axial sacrum and coccyx? Why?

Empty the urinary bladder and bowel content because it may interfere with the image

Position of patient for the AP/PA axial sacrum and coccyx

• place patient in supine position for AP

• Prone position can be used without appreciable loss of detail and is particularly appropriate for patients with a painful injury or destructive disease

Position of part for the AP/PA axial sacrum and coccyx

• with the patient either supine or prone center the MSP of the body to the midline of the table grid

• Adjust patient so that the ASIS are equidistant from the grid

• Have patient flex elbows and place the arms in a comfortable bilaterally symmetric position

• When supine position is used, place a supper under the patients knees

Respiration for AP/PA axial sacrum and coccyx

Suspend

Central ray for AP/PA axial sacrum

• with patient supine direct the CR 15 degrees cephalad and center it to a point 2 inches superior to the pubic symphysis

• With patient prone angle the CR 15 degrees caudad and center it to the clearly visible sacral curve

Central ray for AP/PA axial coccyx

• with the patient supine, direct the CR 10 degrees caudad and center it to a point 2 inches superior to the pubic symphysis

• With the patient prone, angle the CR 10 degrees cephalad and center it to the easily palpable coccyx

• Center IR to CR

Collimation for AP/PA axial sacrum

10×12

Collimation for AP/PA axial coccyx

8×10

Structures shown for AP/PA axial sacrum and coccyx

Sacrum and coccyx free of superimposition

Evaluation criteria for AP/PA axial sacrum

• proper collimation

• Sacrum centered and seen in its entirety

• Sacrum free of foreshortening, with the sacral curvature straightened

• Pubic bones not overlapping sacrum

• No rotation of the sacrum, as demonstrated by symmetric alae

Evaluation criteria for AP/PA axial coccyx

• proper collimation

• Coccyx centered and seen in its entirety

• Coccygeal segments not superimposed by pubic bones

• No rotation of coccyx, as demonstrated by distal segment in line with pubic symphysis

Label # 42 AP axial sacrum

A. Coccyx

B. Sacrum

C. Pubic symphysis

Label #43 AP axial sacrum

A. Sacrum

B. Left sacral wing

C. Sacral foramina

D. Right Ala

E. Right sacroiliac joint

What’s wrong with #35 AP axial sacrum

• centered too superior

• Entire sacrum not shown

• Need to decrease angle to see all of sacrum

• Rotated/ slightly RPO

• patient has not voided

• Not collimated

What’s wrong with #36 AP axial sacrum

• not voided

• Rotated too much to the left

What’s wrong with #37 AP axial coccyx

• not collimated

• Centered superiorly

• Not voided

Position of patient for lateral sacrum/ coccyx

ask patient to turn onto indicated side and flex hips and knees to a comfortable position

Position of part for lateral sacrum/ coccyx

• adjust arms in a position at right angles to the body

• Superimpose the knees and if needed place positioning sponges under and between the ankles and between the knees

• Adjust a support under the body to place the long axis of the spine horizontal. Interiliac plane should be perpendicular to the IR

• Adjust the pelvis and shoulders so that the true lateral position can be maintained

• Center the sacrum or coccyx to the midline of the grid for accurate positioning

Respiration for lateral sacrum/ coccyx

Suspend

Central ray for lateral sacrum

• Elevated ASIS is easily palpated and found on all patients when they are lying on their side

• Perpendicular and directed to the level of the ASIS and to a point 3.5 inches posterior

• Exact position of the sacrum depends on pelvic curve

Central ray for lateral coccyx

• Elevated ASIS is easily palpated and found on all patients when they are lying on their side

• Perpendicular and directed toward a point 3.5 inches posterior to the ASIS and 2 inches inferior

• Exact position of the coccyx depends on the pelvic curve

• Center IR to CR

Collimation for lateral sacrum

10×12

Collimation for lateral coccyx

6×8

Structures shown for lateral sacrum/ coccyx

Sacrum or coccyx

Evaluation criteria for lateral sacrum/ coccyx

• proper collimation

• Presence of lead rubber behind sacrum

• Sacrum and coccyx

• Closely superimposed posterior margins of the ischia and ilia, demonstrating no rotation

Label # 44 lateral sacrum/ coccyx

A. Sacral promontory

B. L5-S1 intervertebral joint space

C. Vertebral body of L5

D. First sacral segment

E. Sacrum

F. Coccyx

What’s wrong with #38 lateral sacrum/ coccyx

• not marked anterior

• Too light

• Too inferior and anterior

• Ala are not superimposed

• Rt femoral head is more anterior

• Rolled forward

• Not collimated