DSA - Intro to Sacrum

Question 1

What are the left and right oblique axis?

Answer 1

Left Oblique axis goes from the Left Side of the base of the sacrum (left sacral sulcus) to the right ILA

Right Oblique Axis goes from the Right Sacral Sulcus to the Left ILA

Question 2

Where is the ST Respiratory Axis?

Answer 2

Superior Transverse Respiratory Axis is a transverse axis about which the sacrum moves during normal respiration

This transverse axis passes through the articular processes posterior to the point of attachment of the dura at S2

Question 3

Where is MT Postural Axis?

Answer 3

Middle Transverse Postural Axis is a transverse axis that passes through the anterior aspect of S2

Question 4

Where is the IT Pelvic/Ilial Axis?

Answer 4

Inferior Transverse Pelvic/Ilial Axis is a transverse axis that passes through the inferior auricular surface at the level of S3

Question 5

How many axes of motions are there for the sacrum?

Answer 5

7

• Anterior/Posterior Axis
• Inferior/Superior Axis
• Left Oblique Axis
• Right Oblique Axis
• Inferior Transverse (Pelvic/Ilial) Axis
• Middle Transverse (Postural) Axis
• Superior Transverse (Respiratory) Axis

Question 6

Describe the natural motion of the lumbar spine and sacrum during respiration

Answer 6

Inspiration:

• Lumbar spine moves anteriorly
• Sacrum Extends (base moves posteriorly; apex moves anteriorly)

Expiration:

• Lumbar spine moves posteriorly
• Sacrum flexes (base moves anteriorly; apex moves posteriorly)

Question 7

What is nutation and counternutation?

Answer 7

Nutation = Flexion of the Sacrum (base moves anteriorly; apex moves posteriorly)

Counternutation = Extension of the sacrum (base moves posteriorly; apex moves anteriorly)

Question 8

What is Lumbarization?

Answer 8

When a 6th lumbar vertebra is present due to failure to fuse with the sacrum

Also only has 4 fused sacral vertebral segments

Can result in a Batwing Deformity, which is when the transverse processes of the L6 are larger and more prominent than normal

Question 9

What is Sacralization?

Answer 9

Incomplete separation and differentiation of the 5th lumbar vertebra (L5) such that it takes on characteristics of a sacral vertebra

Can result in a batwing deformity where the transverse processes are larger than normal and become fused to the sacrum