Introduction to the Sacrum

Question 1

At what level of the sacrum is the inferior lateral angle?

Answer 1

at S4 & S5

Question 2

Name some sacral anterior anatomic landmars

Answer 2

Sacral base
Sacral Promontory
Sacral Apex

Question 3

What is the coccyx?

Answer 3

the lowest part of the spinal column

consists of 4 vertebra

Question 4

What separates adjacent sacral segments?

Answer 4

epiphyseal plates that fuse after puberty

Question 5

Bony articulations of the sacrum

Answer 5

articulates w/ 5th lumbar vertebra superiorly

articulates w/ coccyx inferiorly

Question 6

Sacral Joints

Answer 6

Right SI joint
Left SI joint
L5-S1 intervertebral disc
Sacrococcygeal joint

Question 7

Considerations for SI joint after puberty

Answer 7

in males, SIJ ligaments are well-developed & strong

in females, SIJ ligaments are less developed

Question 8

Considerations for SI joint in 2nd decade of life

Answer 8

ridge develops along iliac surface that interdigitates w/ depression on sacral side to add stability & limits mobility

Question 9

Considerations for SI joint in 3rd decade of life

Answer 9

crescent shape ridge is more pronounced & decreases ROM

some degenerative changes occur on iliac side in males

Question 10

Considerations for SI joint in 4th & 5th decades of life

Answer 10

in males, degenerative changes begin on sacral side

Question 11

SI joint characteristics

Answer 11

L or C shaped with shorter upper arm & longer lower arm

Question 12

Which direction does the apex point?

Answer 12

points anteriorly

Question 13

What type of joint is the SI joint?

Answer 13

diarthrodial joint b/c contains synovial fluid & matching articular surfaces

1 side is hyaline cartilage & other side is fibrocartilage

Question 14

Sacral surface of SI joint

Answer 14

smooth, hyaline cartilage, decreases in width inferiorly & wedged between 2 ilia

Question 15

Iliac surface of SI joint

Answer 15

smooth anteriorly, is fibrous on posterior side (gives rise to interosseous ligaments), fibrocartilage

Question 16

Posterior Sacroiliac Ligament

Answer 16

from 3rd & 4th sacral segments & ascents to PSIS & posterior end of iliac crest

thicker

Question 17

Anterior Sacroiliac Ligament

Answer 17

connects 3rd sacral segment to lateral side of pre-auricular surface

blends w/ iliolumbar ligaments

Question 18

Interosseous Sacroiliac Ligament

Answer 18

major bond between the bones, filling irregular space

covered posteriorly by posterior sacroiliac ligament

Question 19

Long Dorsal SI ligament

Answer 19

connects PSIS to lateral aspect of 3rd & 4th sacral segments

close relationship w/ erector spinae muscles, posterior layer of thoracolumbar fascia & sacrotuberous ligament

Question 20

Sacrospinous Ligament

Answer 20

from ischial spine to lateral margins of sacrum

forms part of origin from which coccygeus ms arise

Question 21

Sacrotuberous ligament

Answer 21

runs from lower sacral tubercles to ischial tuberosity

where gluteus maximus attaches & tendon of biceps femoris attaches

Question 22

What is the role of the sacrospinous & sacrotuberous ligaments?

Answer 22

stabilize to limit posterior-superior rotation of sacral apex around transverse axis

Question 23

Piriformis m

Answer 23

from ant surface of 2-4 lateral masses of sacrum & sacrotuberous ligament to superior border of greater trochanter of femur

externally rotates thigh when hip joint is extended & abducts thigh when hip joint is flexed

Question 24

What can cause sciatica?

Answer 24

piriformis hypertonicity due to chemical reaction that irritates peroneal fibers of the sciatic nerve

causes referred pain down posterior thigh

Question 25

Nervous system of the sacrum

Answer 25

``` Lumbar Plexus (L1-L4) Sacral Plexus (L5-S4) Coccygeal plexus (S5-coccygeal nerve) ```

Question 26

What ganglion are found in sacrum?

Answer 26

inferior mesenteric ganglion superior hypogastric ganglion ganglion impar

Question 27

What are some posterior landmarks used to identify sacral SD?

Answer 27

PSIS AIIS inferior lateral angle L5 spinous process

Question 28

Self-locking mechanism of the sacrum

Answer 28

critical for resistance against shear due to form closure and force closure

Question 29

Force closure

Answer 29

compression produced by body weight, muscle action, and ligament force

Question 30

What is sacral dysfunction related to?

Answer 30

common cause of low back pain & produces many possible viscerosomatic & somatovisceral reflexes

Question 31

What are important to the stability of the SI joint?

Answer 31

postural muscles

Question 32

What are important anterior muscles to the SI joint?

Answer 32

activity of oblique abdominal muscles in both standing & sitting (especially internal obliques)

Question 33

Describe physiological sacral motion

Answer 33

2 oblique axes of sacral motion named according to side of body toward which the superior end of oblique axis is located

Question 34

ST axis

Answer 34

transverse axis about which sacrum moves during respiratory cycle passes from side to side through articular processes posterior to point of attachment of dura @ S2

Question 35

MT axis

Answer 35

functional transverse axis of nutation & counternutation in standing position, passing thru anterior aspect of S2

Question 36

IT axis

Answer 36

functional transverse axis @ level of S3 through inferior auricular surface & represents axis for movement of ilia on sacrum

Question 37

Describe the reciprocal relationship of lumbar spine & sacral base

Answer 37

lumbar flexion with sacral extension lumbar extension w/ sacral flexion

Question 38

Sacral extension counternutation

Answer 38

base tips posterior & apex moves anteriorly

Question 39

Sacral flexion nutation

Answer 39

base tips anteriorly & apex moves posteriorly

Question 40

Principles of sacral motion

Answer 40

all of the movements of the sacrum on ilium are gliding movements

Question 41

How does rotation in lumbar spine affect sacral motion?

Answer 41

causes sacrum to rotate towards the same side & sidebends toward contralateral side

Question 42

How does sidebending in lumbar spine affect sacral motion?

Answer 42

causes sacrum to sidebend towards same side

Question 43

What way does the ilium move?

Answer 43

ilium always moves in same direction as sacrum

Question 44

Lumbarization

Answer 44

transitional segment in which 1st sacral segment becomes like an additional lumbar vertebra articulating w/ 2nd sacral segment

Question 45

Sacrilization

Answer 45

incomplete separation & differentiation of L5 so takes on characteristics of sacral vertebra also caused by TP of L5 being atypically large

Question 46

What does form closure of sacrum require?

Answer 46

proper size, shape & attitude of articulating surfaces