DSA 3: Introduction to Sacrum

Question 1

What are the sacral landmarks?

Answer 1

Sacral base, sacral apex, sacral promontory, Sacral sulcus, ILA, COccyx

Question 2

How does the sacrum change throughout life?

Answer 2

Birth: costal elements, vertebral arch and centrum are cartilage

Age 2-5: vertebral arch fuses with adjacent costal part

Age 8: Fuses with respective centrum

After puberty: Epiphyseal plates fuse from down up, dura attaches at S2 > resulting in 1 sacrum

Question 3

What is the appearance of the SI joint ligaments in males and females after puberty?

Answer 3

Male: SIJ ligaments are well-developed and strong

Female: SIJ ligaments are less developed, allowing mobility during childbirth

Question 4

What is the appearance of the SI joint in a patient’s 20s?

Answer 4

Crescent-shaped ridge develops along the iliac surface which articulates with a depression in the sacrum

Add stability and limits mobility

Question 5

What is the appearance of the SI joint in a patient’s 30s?

Answer 5

Crescent-shaped ridge becomes more pronounced, decreases ROM more

Males: degenerative changes may begin to appear on iliac side

Question 6

What is the appearance of the SI joint in the 4th and 5th decades of life?

Answer 6

Males: Degenerative changes appear on sacral side

Fibrous ankylosis may further limit joint motion

Question 7

What is the SI joint classified as?

Answer 7

Diarthroidal joint - contanis synovial fluid and matching articular surfaces, one side is hyaline and the other side is fibrocartilage

Question 8

Characteristics of the SI joint

Answer 8

L or C shaped with a shorter upper arm and longer lower arm joining at S2

Sacral surface: smooth, hyaline cartilage

Iliac surface: smooth anteriorly, fibrous posteriorly, fibrocartilage

Question 9

What ligament is the major bond between the ilium and the sacrum?

Answer 9

Interosseous Sacroiliac Ligament

Question 10

What is the attachment of the long dorsal SI ligament?

Answer 10

PSIS to the lateral aspect of 3rd and 4th sacral segments

Question 11

What are the differential static landmarks for determining sacral sulcus depth?

Answer 11

Medial to the PSIS

Question 12

What is the purpose of the self-locking mechanism of the sacrum?

Answer 12

Resistance against shear

Question 13

What are the two aspects of the sacral self-locking mechanism?

Answer 13

Form closure

Force closure

Question 14

What is form closure of the sacrum due to?

Answer 14

How the joint fits together, specific properties of the articular surfaces of the SI joint

Question 15

What is force closure of the sacrum due to?

Answer 15

Compression produced by body weight, muscles, and ligaments holding it together

Question 16

What are the dorsal muscles that may affect SI joint stability?

Answer 16

Latissimus dorsi

Thoracolumbar fascia

Gluteus maximus

ITB

Question 17

What are the ventral muscles that may affect SI joint stability?

Answer 17

Abdominal obliques

Transverse abdominals

Linea alba (not a muscle but listed on the slide)

Question 18

Where does the Superior Transverse Axis of the sacrum pass through? When would the sacrum move around this axis?

Answer 18

Posterior aspect of S2

Respiratory cycle

Question 19

Where does the Middle Transverse Axis of the sacrum pass through? When would the sacrum move around this axis?

Answer 19

Anterior aspect of S2

Nutation and counternutation in the standing position

Question 20

Where does the Inferior Transverse axis of the sacrum travel through? When would the sacrum move around it?

Answer 20

S3

Axis of movement of ilia on the sacrum

Question 21

As the lumbar spine extends, what is the sacrum doing?

Answer 21

Flexes

Question 22

As the sacrum extends, what is the lumbar spine doing?

Answer 22

Flexion

Question 23

What is the motion of the sacrum in counternutation?

Answer 23

Sacral extension

Question 24

What is the motion of the sacrum in nutation?

Answer 24

Sacral flexion

(Sacrum needs a drink, tilts foward as the “bowl” of the pelvis tips back)

Question 25

Rotation through the lumbar spine causes what movement of the sacrum?

Answer 25

Rotation towards ipsilateral side

Sidebending to contralateral side

Question 26

Downward force of the lumbar spine onto the sacrum causes what motion of the sacrum?

Answer 26

Nutation (sacral flexion)

Question 27

Traction applied from above the lumbosacral junction causes what motion of the sacrum?

Answer 27

Counternutation (sacral extension)

Question 28

Sidebending applied through the lumbar spine causes what motion of the sacrum?

Answer 28

Sidebending to the ipsilateral side

Question 29

What is the relationship of the movements of ilium and sacrum?

Answer 29

Move in the same direction

Question 30

An occipital condylar compression can cause what to occur in the sacrum?

Answer 30

Lowered sacral base on the ipsilateral side

Question 31

What is occurring in this XR?

Answer 31

Lumbarization of S1

May be unilateral or bilateral

Question 32

What is occurring in this XR?

Answer 32

Sacralization of L5

Note: atypically large TPs of L5

Bat wing deformity

May be unilateral or bilateral

Question 33

Sacrum dysfunction will commonly manifest as what symptom?

Answer 33

Chronic low back pain

Question 34

What are the two criteria for a compensated lumbar spine?

Answer 34

1. Lumbar spine is rotated toward the deep sulcus (PTP and deep sulcus on the same side)
2. Lumbar spine should be sidebent toward the axis in the case of a torsion

Question 35

What is the position of the compensated L5 for a flexed sacrum?

Answer 35

Neutral (Type 1 spinal mechanics)

Question 36

What is the position of the compensated L5 for an extended sacrum?

Answer 36

Flexed or extended (Type 2 Spinal mechanics)