Sacrum, Coccyx, SI joints positioning notes/ demo

SI joints views

AP axial, RPO and/OR LPO

AP axial SI joint technique

90 kVp, 14 mAs, center cell

SI joints & Sacrum/coccyx- breathing/ SID

suspended expiration

40” SID

Ap axial SI joint overview

Collimation

• 12×10 CW

Centering

• 1.5” superior to symph & down the MSP

  • Males- 30 cephalad angle

  • Females- 35 cephalad angle

AP SI joint- angle for males

30 cephalad

AP SI joint- angle for females

35 cephalad

AP SI joints- evaluation criteria

• lumbosacral junction & sacrum

• open intervertebral disk space between L5 & S1

• both SI joints

merrill’s collimation for SI joints

• 10×8 CW

merrills breathing for SI joints & sacrum/coccyx

suspended RESPIRATION

merrills note for AP SI joints

• images can be taken prone if pt cannot tolerate lying on back

• central ray MUST be angle CAUDAD

Too much angle- AP SI joint

pubic bone overlies SI joints

Too little angle- AP SI joints

SI joints are foreshortened & closed off

w/ proper angle- AP SI joints

pubic bone overlies distal coccyx

RPO & LPO SI joints- technique

90 kVp, 16 mAs, center cell

RPO & LPO SI joints: overview

Collimation

• 6×10 LW

Patient position

• 25-30 degree oblique (side of interest is UP)

Centering

• perpendicular to IR & 1” medial to elevated ASIS

Marker placement

• lateral on ELEVATED SIDE

RPO & LPO SI joints- what joint is demonstrated?

Joint FARTHEST FROM THE IR (ELEVATED SIDE)

RPO & LPO SI joints- evaluation criteria

• open SI joint space FARTHEST from IR w/ minimal overlapping of ilium & sacrum

• joint centered

Under rotation-RPO & LPO SI joints

iliac tuberosity is overlapping sacral ala/ sacrum is sitting in inlet (like AP)

joint is closed off at

over rotation RPO & LPO SI joints

sacrum is under pelvis, can see scotty dogs, SI joint closed off at

proper rotation RPO & LPO SI joints

border of sacrum just inside the inlet

picture of…..

inlet of pelvis

SI joint special view: RAO/ LAO purpose

SI joint CLOSEST to IR is visualized

SI joint special view: RAO/ LAO summary

Pt position

• prone, side of interest rotated away from table 25-30 degrees

Marker placement

• mark lateral on side CLOSEST TO TABLE

Sacrum/coccyx views

AP sacrum/ coccyx & Lateral sacrum/ coccyx

RH note for sacrum coccyx

if physician orders only a sacrum or only a coccyx, DO BOTH

bladder stim replacement= DO BOTH

merrills recommends what for sacrum coccyx

pre procedure bowel prep

AP axial Sacrum technique

90 kVp, 14 mAs, center cell

AP axial Sacrum- overview

Collimation

• 10×12 LW

Centering

• angled 15 cephalad

• center 2” superior to symph (bisect symph & asis)

Marker placement

• bottom!

AP axial Sacrum evaluation criteria

• sacrum centered & seen entirely (base to apex)

• sacrum free of foreshortening, w/ sacral curve straightened (why we angle)

• no rotation of sacrum, as demonstrated by symmetric alae & spinous processes down middle (sacrum is in line w/ symph)

merrills recommendation for sacrum & coccyx AP- pt position

place support under patient’s knees

merrills note for Ap sacrum when patient is prone

angle 15 CAUDAD through sacral curve

on a good AP sacrum, the pubic bone lays…

on top of coccyx

too much angle AP axial Sacrum

pubic bone overlaps sacrum

not enough angle AP axial Sacrum

sacrum looks foreshortened & pubic bone lays distal end of coccyx

how to note rotation AP axial Sacrum

that side is flatter & obturator foramen isn’t oval & nicely opened
(coccyx goes opposite way that it is rotated)

AP coccyx- technique

85 kVp, 14 mAs, center cell

AP coccyx- overview

Collimation

• 6×8 LW

Centering

• angled 10 caudad (to get coccyx free of superimposition)

• then, center 2” superior to symph (bisect symph & ASIS)

Marker placement

• bottom

note for marker placement on AP sacrum to ap coccyx

place marker where cross hair is on AP sacrum, so when you add angle tot he tube, you know where to center again

AP coccyx-evaluation criteria

• coccyx centered & seen entirely

• coccygeal segments not superimposed by pubic bones

• no rotation of coccyx, as demonstrated by distal segment in line with symph

merrills note for AP coccyx- if patient is prone

angle 10 degrees cephalad through coccyx

AP coccyx- not enough angle

pubic bones are over coccyx

sacrum left lateral- technique

96 kVp, 45 mAs, center cell

sacrum left lateral overview

Collimation

• 10×12 LW

Centering

• perpendicular & directed 3.5” POSTERIOR to ASIS

Marker placement

• left marker ANTERIOR

sacrum left lateral- evaluation criteria

• sacrum (L5/S1 to coccyx)

• closely superimposed posterior margins of ischia & ilia, demonstrating no rotation

merrills note for sacrum left lateral & coccyx left lateral

• place lead rubber absorbed behind patient to absorb scatter

  • recommends support under waist to keep spine HORIZONTAL to IR

rotation on sacrum left lateral

• femoral heads/sciatic notches are not stacked/superimposed

trick going from lateral sacrum to lateral coccyx

bring centering down 2”

coccyx left lateral- technique

85 kVp, 40 mAs, center cell

coccyx left lateral- overview

Collimation

• 6×8 LW

Centering

• perpendicular & 3.5” posterior & 2” inferior from ASIS

Marker placement

• left anteriorly

coccyx left lateral- evaluation criteria

• coccyx

• closely superimposed posterior margins of the ischia & ilia, demonstrating no rotation

SPECIAL VIEW: sacrum & coccyx technique

96 kVp, 45 mAs, center cell

SPECIAL VIEW: sacrum & coccyx overview

Collimation

• 10×12 LW

Centering

• perpendicular & 3-4” POSTERIOR to ASIS

  • (may need to be moved 1” inferior to ASIS to include all anatomy)

• SUSPENDED RESPIRATION