L-Spine, Sacrum, and Coccyx

Question 1

AP (or PA) L-Spine

Answer 1

• Pt is supine with knees flexed drawn up to flatten spine
• 48” SID (to reduce distortion/open disk spaces)
• center IR and CR at MSP at level of iliac crest
• expose on expiration
• image should show lower T-spine to the sacrum
• open disk spaces
• PA is used b/c beam divergence matches angle of vertebral bodies / to reduce pt dose

Question 2

Lateral L-Spine

Answer 2

• Pt is in recumbent-lateral position - affected side down
• superimpose knees, hips, and shoulders
• center at iliac crest, and MCP
• angle 5 (males) or 8 (females) degrees caudad
• expose on expiration
• anatomy shown from T11/12 to coccyx
• open intervertebral disk spaces

Question 3

Lateral Lumbosacral Junction

Answer 3

• Also called a “L5/S1 Spot”
• same angle and pt position as Lateral L-Spine
• *center IR to 2” posterior to ASIS and 1.5” inferior to iliac crest
• *image should show open L5/S1 junction

Question 4

AP Oblique L-Spine (Zygapophyseal Joints)

Answer 4

• oblique Pt 45 degrees affected side down
• arms out of FOV
• CR centered to 2” medial to elevated ASIS and 1.5” superior to iliac crest
• expose on expiration
• image should show classic “Scottie Dog” appearance
• zygapophyseal joints closest to IR

Question 5

PA Oblique L-Spine (Zygapophyseal Joints)

Answer 5

• Oblique Pt 45 degrees affected side up
• Pt position and IR centering same as AP Oblique
• image should show zygapophyseal joints farthest from IR

Question 6

AP Axial Lumbosacral Junction and SI Joints

Answer 6

• also called AP Spot
• Pt supine
• CR centered at 1.5” superior to pubic symphysis and 2-2.5” inferior to ASIS
• angle 30 (males) or 35 (females) degrees cephalad
• image should show SI Joints and L5/S1 junction

Question 7

AP Axial Sacrum/Coccyx

Answer 7

• Pt supine
• Center IR to 2” superior to pubic symphysis
• Sacrum: angle 15 degrees cephalad
• Coccyx: angle 10 degrees caudad
• image should show respective anatomy without bony superimposition
• no rotation

Question 8

Lateral Sacrum/Coccyx

Answer 8

• Pt in true lateral position: shoulders, hips, and flexed knees on top of each other
• place support under waist to make spine parallel with IR
• Sacrum: center IR 3.5” posterior to ASIS
• Coccyx: center IR 3.5” posterior and 2” inferior to ASIS
• image should show anatomy of interest with no rotation