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Year 1: 2020 OS II Midterm > DSA 3: Introduction to Sacrum > Flashcards

DSA 3: Introduction to Sacrum Flashcards

1
Q

The sacrus is formed by the union of how many modified vertebrae?

A

5 modified vertebrae

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2
Q

What does the sacrum articulate with?

A
  • Superiorly: 5th lumbar vertebra
  • Inferiorly: coccyx
  • Laterally: Os Coxae (inominates) through C shaped SI articulations
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3
Q

What are the four sacral joints?

A
  1. Right SI Joint
  2. Left SI Joint
  3. L5-S1 Intervertebral disc
  4. Sacrococcygeal Joint
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4
Q

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

A
  • Male: SIJ ligaments are well-developed and strong
  • Female: SIJ ligaments are less developed, allowing mobility during childbirth
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5
Q

What is the appearance of the SI joint in a patient in his or her 20s?

A
  • Crescent-shaped ridge develops along the iliac surface which articulates with a depression in the sacrum
  • Add stability and limits mobility
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6
Q

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

A

Crescent-shaped ridge becomes more pronounced, decreases ROM more

Males: degenerative changes may begin to appear on iliac side

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7
Q

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

A
  • Males: Degenerative changes appear on sacral side
  • Fibrous ankylosis may further limit joint motion
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8
Q

What is the SI joint classified as?

A

Diarthroidal joint - contanis synovial fluid and matching articular surfaces

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9
Q

What does the posterior sacroiliac ligament connect?

A
  • Origin: Third and fourth sacral segments
  • Insertion: PSIS and posterior end of internal lip of iliac crest

Thicker than Anterior Sacroiliac Joint

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10
Q

What does the anterior sacroiliac ligament connect?

A
  • Origin: Third sacral segment
  • Insertion: Lateral side of pre-auricular sulcus
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11
Q

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

A

Interosseous Sacroiliac Ligament

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12
Q

What is the attachment of the long dorsal SI ligament?

A

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

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13
Q

When does the long dorsal SI joint become stretched?

A

When the sacrum is rotated posteriorly relative to the ilium (counternutation):

  • Early stages of pregnancy
  • Aging & Degeneration
  • Backward torsions or unilateral/bilateral sacral extensions
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14
Q

Where is the sacrospinous ligament found?

A
  • Origin: Ischial spine
  • Insertion: Lateral margins of sacrum

Origin of coccygeus muscles

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15
Q

Where is the sacrotuberous ligament found?

A
  • Origin: Lower sacral tubules
  • Insertion: Ischial tuberosity

Connects with fascia of pelvis

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16
Q

What is the role of sacrospinous and sacrotuberous ligaments?

A

Stabilize to limit posterior-superior rotation of the sacral apex around a transverse axis

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17
Q

Where is the piriformis muscle found?

A
  • Origin: Antertior surface fo sacrum and sacrotuberous ligament
  • Insertion: Superior border fo greater trochanter of femur
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18
Q

What is the function of the piriformis?

A
  • Externally rotate thigh when hip is extended
  • Abduct thight when hip is flexed
  • Holds femoral head in acetabulum
19
Q

What nerve plexuses and ganglion can be found in the sacrum area?

A
  • Lumbar Plexus (L1-4)
  • Sacral Plexus (L5-S4)
  • Coccygeal Plexus (S5-Coccygeal nerve)
20
Q

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

A

Resistance against shear

21
Q

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

A

Form closure

Force closure

22
Q

What is form closure of the sacrum due to?

A

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

23
Q

What is force closure of the sacrum due to?

A

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

24
Q

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

A
  • Latissimus dorsi
  • Thoracolumbar fascia
  • Gluteus maximus
  • Iliotibial Band
25
Q

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

A

Abdominal obliques

Transverse abdominals

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

26
Q

Where does the Superior Transverse Axis of the sacrum pass through?

When would the sacrum move around this axis?

A

Posterior aspect of S2

Respiratory cycle

27
Q

Where does the Middle Transverse Axis of the sacrum pass through?

When would the sacrum move around this axis?

A

Anterior aspect of S2

Nutation and counternutation in the standing position

28
Q

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

A

S3

Axis of movement of ilia on the sacrum

29
Q

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

A

Flexes

30
Q

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

A

Flexion

31
Q

What is the motion of the sacrum in counternutation?

A

Sacral extension

  • Base moves posteriorly
  • Apex moves anteriorly
32
Q

What is the motion of the sacrum in nutation?

A

Sacral flexion

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

33
Q

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

A

Rotation towards ipsilateral side

Sidebending to contralateral side

34
Q

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

A

Nutation (sacral flexion)

35
Q

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

A

Counternutation (sacral extension)

36
Q

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

A

Sidebending to the ipsilateral side

37
Q

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

A

Ilium moves in the same direction but in lesser degree

38
Q

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

A

Lowered sacral base on the ipsilateral side

39
Q

What is occurring in this x-ray?

A

Lumbarization of S1

  • May be unilateral or bilateral
40
Q

What is occurring in this x-ray?

A

Sacralization of L5

Note: atypically large TPs of L5

Bat wing deformity

May be unilateral or bilateral

41
Q

Sacrum dysfunction will commonly manifest as what symptom?

A

Chronic low back pain

42
Q

What are the two criteria for a compensated lumbar spine?

A
  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
43
Q

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

A

Neutral (Type 1 spinal mechanics)

44
Q

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

A

Flexed or extended (Type 2 Spinal mechanics)

Year 1: 2020 OS II Midterm (15 decks)

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