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Pelvic Girdle - Biomechanics Flashcards

1
Q

What are the 4 ligaments of the pelvic girdle?

A
  • Iliolumbar ligament
  • Ventral sacroiliac ligament
  • Sacrotuberous ligament
  • Sacrospinous ligament
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2
Q

What ligament attaches the L-spine to the innominate bone?

A

Iliolumbar ligament

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3
Q

What are the 4 joints/ aspects of the pelvic girdle system?

A
  • Lower L-spine
  • Sacroiliac joints
  • Pubic symphysis
  • Hip joint
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4
Q

What type of joint is the pubic symphysis?

A
  • Amphiarthrodial
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5
Q

What is the function of the pubic symphysis?

A
  • Increases stability at the sacroiliac joints
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6
Q

What 2 structures provide stability at the pubic symphysis?

A
  • Fibrocartilaginous disc

- Arcurate ligaments

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7
Q

What type of joints are the sacroiliac joints?

A
  • Diarthrodial (synovial) –> Become amphiarodial with age
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8
Q

How do the shape of the articulations of the sacroiliac joints change with age?

A
  • They are flat until puberty when they develop grooves and ridges
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9
Q

Which aspect of the sacroiliac joints are covered with hyaline cartilage, and which are covered with fibrocartilage? Which surface of the sacroiliac joint is thicker?

A
  • Sacral surface covered with hyaline/ thicker

- Ilial surface covered in fibrocartilage

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10
Q

Which aspect of the sacroiliac joint is susceptible to osteoarthritis?

A
  • Ilial surface
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11
Q

What is the shape of the articular surface of the SIJ in the sagittal plane?

A
  • Kidney shaped
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12
Q

How is the long arm of the sacroiliac joint oriented?

A

Anterior-posterior

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13
Q

How is the short arm of the sacroiliac joint oriented?

A

Superior-inferior

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14
Q

At which levels of the sacrum does the sacroiliac joint articulate? (males/ females)

A

Males: S1 - S3/4
Females:S1 - S2

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15
Q

What spinal segments innervate the anterior capsule of the SIJ? Which spinal segments innervate the posterior capsule of the SIJ?

A

L2 - S2

L4 - S4

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16
Q

What are the 3 function sof the pelvic girdle?

A
  • Base for superincumbent body weight
  • Links the body to the lower extremities
  • Supports the viscera
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17
Q

What 5 structures form the posterior arch of the pelvic girdle?

A
  • Lower extremities
  • Acetabulae
  • Ilia
  • Sacroiliac joint
  • Upper 3 sacral vertebra
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18
Q

What 5 structures form the anterior arch of the pelvic girdle?

A
  • Lower extremities
  • Acetabulae
  • Pubic bones
  • Disc
  • Pubic symphysis
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19
Q

Describe the 3 factors causing the keystone effect of the pelvic girdle.

A
  • Innominate bones produce lateral to medial forces against the sacrum from the arches
  • Sacrum is wider at base wedges into the innominate bones
  • Body weight presses the sacrum into the innominate bones
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20
Q

What is meant by form closure?

A
  • Structure of the bony arches creates stability
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21
Q

What is meant by force closure?

A
  • Core muscles support pelvic girdle
  • Transverse abdominis
  • Pelvic floor muscles
  • Diaphragm
  • Lumbar multifidi
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22
Q

What are 2 common historical findings that may change form closure of the pelvis?

A
  • Child birth

- Multitrauma (fall from heights, MVAs)

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23
Q

What are the 3 effects of a horizontally oriented sacrum?

A
  • Increased lumbosacral angle
  • Increased load to anterior ligaments
  • More risk to SIJ
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24
Q

What are the 3 effects of a vertically oriented scarum?

A
  • Decreased lordosis
  • Loose packed position of lumbar spine
  • More risk to lumbar spine
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25
Q

Which gender is more likely to have a horizontally oriented sacrum?

A
  • Females
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26
Q

Which gender is more likely to have a vertically oriented sacrum?

A
  • Male
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27
Q

What determines the shape of the SI joint?

A
  • The development of the spinal curves

more development –> more motion at SI joint

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28
Q

Which sacral position is more dynamic? Which is more static?

A

Horizontal –> Dynamic

Vertical –> Static

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29
Q

What are the 3 axes of motion of the ilia? Through which structures do they pass, and what motion occurs around them?

A 
Horizontal axis:
- Through SIJs
- Anterior/ posterior rotation
Oblique A/P axis
- Through SIJ and pubic symphysis
- Inflare/ outflare motion
Straight translation:
- Upslip / downslip motion
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30
Q

What are the 2 axes of motion at the pubis?

A

Horizontal axis

  • Through pubic symphysis
  • Anterior / posterior rotation

Translation:

  • Upslip
  • Downslip
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31
Q

What are the 3 axes of motion of the sacrum?

A
  • Sagittal axis
  • Vertical axis
  • Horizontal axis
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32
Q

At what level does the sagittal axis pass through the sacrum? What motion occurs at this axis?

A
  • Through S2

- R and L sidebend

33
Q

At what level does the vertical and horizontal axis pass through the sacrum?

34
Q

What motion occurs about the vertical axis of the sacrum?

A

R and L rotation

35
Q

What motion occurs about the horizontal axis of the sacrum?

A
  • Flexion/ nutation

- Extension/ counternutation

36
Q

Describe the 2 motions occurring during nutation.

A
  • Sacrum moves inferiorly along the short arm of the SI, and posteriorly along the long arm of the SI joint
37
Q

What 2 structures check excessive nutation?

A
  • Sacrotuberous ligament

- Interosseus ligament

38
Q

Describe the 2 motions occuring during counternutation.

A
  • Sacrum move superiorly on short arm of the SI, and anteriorly along the long arm of the SI joint
39
Q

What 2 structures check excessive counternutation of the SI joint?

A
  • Long dorsal SI ligament

- Multifidus muscle

40
Q

What is the ROM of counternutation?

A
  • Similar to extension at the elbow, the sacrum only performs counternutation when returning to neutral
41
Q

What are the only 2 instances in which the sacrum moves into a counternutated position?

A
  • Lying supine and relaxed due to a lack of form and force closure
  • End range forward bending in Pt’s with tight hamstrings
42
Q

What are the 2 types of forward torsions?

A

R on Right axis

L on Left Axis

43
Q

What are the 2 types of backward torsions?

A

R on Left Axis

L on Right Axis

44
Q

What combined motions do the oblique axes of the sacrum give rise to?

A
  • Minimal sidebend

- Rotation

45
Q

What are the 2 pelvic movements during inhalation in prone?

A
  • Sacrum extends relative to innominants

- Innominats anteriorly rotate relative to sacrum

46
Q

What are the 2 pelvic movements during exhalation in prone?

A
  • Sacrum flexes relative to innominants

- Innominants posteriorly rotates relative to sacrum

47
Q

During forward flexion, the L-spine flexes (reversing lordosis). What occurs in the pelvis?

A
  • Sacrum extends relative to L-vertebrae, opening L5-S1 facets
  • Sacrum nutates (relative to innominants)
  • Innominants outflare
  • Hips shift posteriorly
  • Pelvic girdle rotates anteriorly on the hips (hip flexion)
48
Q

What pelvic movements occur during backward bending?

A
  • Lumbar lordosis increases/ extends
  • Sacrum flexes relative to lumbar spine/ closes L5-S1 facet
  • Sacrum nutates relative to innominates
  • Hips shift anteriorly
  • Pelvic girdle rotates posteriorly on the hips (hip extension)
49
Q

What pelvic movements occur during side bending?

A

For R sidebend

  • Pelvic girdle side bends L
  • R hip adducts; L hip abducts
  • R innominate posteriorly rotates
  • L innominate anteriorly rotates
  • Sacrum rotates R on R axis/ forward sacral torsion
  • L5/S1 Rotates R, sidebends R
  • Lumbar segments sidebend left, rotate right (because it is in neutral)
50
Q

What pelvic movements occur during left rotation?

A
  • R femur translates anteriorly
  • R femur ERs
  • L femur translates posteriorly
  • L femur IRs
  • R innominant anteriorly rotates
  • L innominant posteriorly rotates
  • Sacrum rotates L on L (forward sacral torsion)
  • Lumbar spine L rotates (type II at L5-S1; type I at the rest of the L-spine)
51
Q

Describe the pelvic movements during sit to stand transfers?

A
  • Upper trunk flexed to shift weight forward
  • L-spine flexes reversing lordosis
  • Sacrum extended
  • Innominants rotated anteriorly
  • Trunk extends as LE accepts weight
  • Hip extends with hip extensors initiating posterior rotation
  • L5 extends over S1
  • Sacrum moves into flexion
  • Lordosis reverses
52
Q

What ligaments are stressed as the hip extends during the end of sit to stand transfers?

A
  • Sacrotuberous ligaments

- Sacrospinous ligaments

53
Q

What motion defined by Greenman occurs during locomotion? What are the 2 combined motions?

A
  • Wobble occurs throughout gait
    Combined:
  • Forward torsion around oblique axis
  • Slight sidebending to opposite side
54
Q

What is the position of the sacrum, trunk and innominants at R heel strike?

A
  • R innominant rotated posteriorly
  • L innominant rotated anteriorly
  • Trunk rotated to the L
  • Sacrum rotated to the L
55
Q

What is the position of the sacrum, trunk, and innominants at R midstance?

A
  • R innominant rotating anteriorly
  • L innominant rotating posteriorly
  • Trunk sidebent R, rotated L
  • Sacrum rotated R on R with slight side bend L
56
Q

How does pelvis motion change from straight ambulation to stair ascension/ descension?

A
  • Same, but with greater ROM
57
Q

How is the motion of the innominants named?

A
  • The direction of the cephalad end of the pelvis
58
Q

What muscle causes a forward torsion lesion of the sacrum (RonR or LonL)?

A
  • Contralateral piriformis
59
Q

What motion causes a forward torsion lesion?

A
  • The sacrum goes through normal forward torsion such as gait, and does not rotate all the way back
  • Think about the contralateral (to the axis) facet being “stuck closed”
60
Q

How do backward torsion lesions typically occur?

A
  • Lumbar spine is flexed or extended and then undergoes trauma
  • Think of contralateral facet as being stuck open
61
Q

Describe the position of the sacral base, inferior lateral angle of the sacrum, lumbar lordosis, the result of the sitting flexion test, and the effect of moving from flexion to extension in a LonL Forward Torsion lesion.

A

Sacral base: Deep on right
ILA: Posterior, and inferior (prominent) on left
Lumbar lordosis: Increased
Sitting Flexion Test: + on the right (PSIS moves further cranially)
Flex –> Ext: Landmarks equalize

62
Q

Describe the position of the sacral base, inferior lateral angle of the sacrum, lumbar lordosis, the result of the sitting flexion test, and the effect of moving from flexion to extension in a RonR Forward Torsion lesion.

A

Sacral base: Deep on left
ILA: Posterior, and inferior (prominent) on right
Lumbar lordosis: Increased
Sitting Flexion Test: + on the left (PSIS moves further cranially)
Flex –> Ext: Landmarks equalize

63
Q

Describe the position of the sacral base, inferior lateral angle of the sacrum, lumbar lordosis, the result of the sitting flexion test, and the effect of moving from flexion to extension in a RonL Backward Torsion lesion.

A

Sacral base: Deep on left
ILA: Posterior, and inferior (prominent) on right
Lumbar lordosis: Decreased
Sitting Flexion Test: + on the right (PSIS moves further cranially)
Flex –> Ext: Landmarks worsen

64
Q

Describe the position of the sacral base, inferior lateral angle of the sacrum, lumbar lordosis, the result of the sitting flexion test, and the effect of moving from flexion to extension in a LonR Backward Torsion lesion.

A

Sacral base: Deep on right
ILA: Posterior, and inferior (prominent) on left
Lumbar lordosis: Decreased
Sitting Flexion Test: + on the left (PSIS moves further cranially)
Flex –> Ext: Landmarks worsen

65
Q

Which type of forward torsion is more common? (LonL or RonR)?

A

L on L (85 %)

66
Q

Which type of backward torsion is more common? (RonL or LonR)?

A

R on L (85 %)

67
Q

What type of sacral lesion is common postpartum?

A
  • Bilateral sacral flexion
68
Q

How is the sacrum positioned in a bilateral sacral flexion lesion?

A
  • Stuck in nutation around middle transverse axis

- Can think of it as both L5-S1 facets stuck closed

69
Q

How is the sacrum positioned in a bilateral sacral extension lesion?

A
  • Think of it as both L5-S1 facets stuck open
70
Q

What are the 2 types of sacral shears?

A

Unilateral sacral flexion
- L5-S1 facet stuck closed unilaterally, but with large sidebend component
Unilateral Sacral Extension
- L5-S1 facet stuck open unilaterally, but with large sidebend component

71
Q

What are the 2 types of vertical axis rotations?

A
  • Anterior

- Posterior

72
Q

Which 3 types of sacral lesions are uncommon?

A
  • Bilateral sacral extension
  • Sacral shear
  • Vertical axis rotations
73
Q

How are the 4 landmarks oriented in a posterior rotation iliosacral lesion?

A

PSIS: Lower
ASIS: Higher
Pubic Tubercle: Higher
Ischial tubercle: Deeper

74
Q

How are the 4 landmarks oriented in an anterior rotation iliosacral lesion?

A

PSIS: Higher
ASIS: Lower
Pubic Tubercle Lower:
Ischial tubercle:More shallow

75
Q

How are the 4 landmarks oriented in an upslip iliosacral lesion?

A

PSIS: Higher
ASIS: Higher
Pubic Tubercle: Higher
Ischial tubercle: Higher

76
Q

How are the 4 landmarks oriented in a downslope iliosacral lesion?

A

PSIS: Lower
ASIS: Lower
Pubic Tubercle: Lower
Ischial tubercle: Lower

77
Q

How are the 4 landmarks oriented in an inflare iliosacral lesion?

A

PSIS: Lateral
ASIS: Medial
Pubic Tubercle: No change
Ischial tubercle: Lateral

78
Q

How are the 4 landmarks oriented in an outflate iliosacral lesion?

A

PSIS: Medial
ASIS: Lateral
Pubic Tubercle: No change
Ischial tubercle: Medial

79
Q

What type of lesion may occur at the pubic region?

A

Pubic shears.

MS II (20 decks)

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