Pelvic Girdle - Biomechanics Flashcards
What are the 4 ligaments of the pelvic girdle?
- Iliolumbar ligament
- Ventral sacroiliac ligament
- Sacrotuberous ligament
- Sacrospinous ligament
What ligament attaches the L-spine to the innominate bone?
Iliolumbar ligament
What are the 4 joints/ aspects of the pelvic girdle system?
- Lower L-spine
- Sacroiliac joints
- Pubic symphysis
- Hip joint
What type of joint is the pubic symphysis?
- Amphiarthrodial
What is the function of the pubic symphysis?
- Increases stability at the sacroiliac joints
What 2 structures provide stability at the pubic symphysis?
- Fibrocartilaginous disc
- Arcurate ligaments
What type of joints are the sacroiliac joints?
- Diarthrodial (synovial) –> Become amphiarodial with age
How do the shape of the articulations of the sacroiliac joints change with age?
- They are flat until puberty when they develop grooves and ridges
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?
- Sacral surface covered with hyaline/ thicker
- Ilial surface covered in fibrocartilage
Which aspect of the sacroiliac joint is susceptible to osteoarthritis?
- Ilial surface
What is the shape of the articular surface of the SIJ in the sagittal plane?
- Kidney shaped
How is the long arm of the sacroiliac joint oriented?
Anterior-posterior
How is the short arm of the sacroiliac joint oriented?
Superior-inferior
At which levels of the sacrum does the sacroiliac joint articulate? (males/ females)
Males: S1 - S3/4
Females:S1 - S2
What spinal segments innervate the anterior capsule of the SIJ? Which spinal segments innervate the posterior capsule of the SIJ?
L2 - S2
L4 - S4
What are the 3 function sof the pelvic girdle?
- Base for superincumbent body weight
- Links the body to the lower extremities
- Supports the viscera
What 5 structures form the posterior arch of the pelvic girdle?
- Lower extremities
- Acetabulae
- Ilia
- Sacroiliac joint
- Upper 3 sacral vertebra
What 5 structures form the anterior arch of the pelvic girdle?
- Lower extremities
- Acetabulae
- Pubic bones
- Disc
- Pubic symphysis
Describe the 3 factors causing the keystone effect of the pelvic girdle.
- 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
What is meant by form closure?
- Structure of the bony arches creates stability
What is meant by force closure?
- Core muscles support pelvic girdle
- Transverse abdominis
- Pelvic floor muscles
- Diaphragm
- Lumbar multifidi
What are 2 common historical findings that may change form closure of the pelvis?
- Child birth
- Multitrauma (fall from heights, MVAs)
What are the 3 effects of a horizontally oriented sacrum?
- Increased lumbosacral angle
- Increased load to anterior ligaments
- More risk to SIJ
What are the 3 effects of a vertically oriented scarum?
- Decreased lordosis
- Loose packed position of lumbar spine
- More risk to lumbar spine
Which gender is more likely to have a horizontally oriented sacrum?
- Females
Which gender is more likely to have a vertically oriented sacrum?
- Male
What determines the shape of the SI joint?
- The development of the spinal curves
more development –> more motion at SI joint
Which sacral position is more dynamic? Which is more static?
Horizontal –> Dynamic
Vertical –> Static
What are the 3 axes of motion of the ilia? Through which structures do they pass, and what motion occurs around them?
Horizontal axis: - Through SIJs - Anterior/ posterior rotation Oblique A/P axis - Through SIJ and pubic symphysis - Inflare/ outflare motion Straight translation: - Upslip / downslip motion
What are the 2 axes of motion at the pubis?
Horizontal axis
- Through pubic symphysis
- Anterior / posterior rotation
Translation:
- Upslip
- Downslip
What are the 3 axes of motion of the sacrum?
- Sagittal axis
- Vertical axis
- Horizontal axis