L6.2 Bones & joints of pelvis Flashcards
1
Q
True and false pelvis
A
- Pelvis divides into true (lesser - which contains the viscera) & false (greater - above the true pelvis) pelvis
- Iliopectineal line → subdivides false pelvis from true pelvis
2
Q
Difference between female and male pelvis shape
A
- Wider and shorter pelvis and have wider pubic arches
- 50% of females have gynaecoid shaped pelvis
- 30% of females have android pelvis
- Narrower, longer & funnel shaped → complications of birth
- 20% of females have Anthropoid shaped pelvis (ape-like)
- Or 2% have paltypelloid
- Most males have android shaped pelvis
3
Q
Difference between male and female pelvic inlet
A
- Female pelvis:
- Wide inlet
- Ischial spine does not project MED as much
- Male pelvis
- Heart shaped inlet
- Ischial spine projects into MED plane
4
Q
Line of gravity and pelvic tilt
A
- Tilt: Pubis becomes INF (in line with lumbosacral joint)
- Accommodated by changes in the lumbar spine & aligns with center of gravity
- Females have a greater pelvic tilt (due to lumbar lordosis)
5
Q
Key features of the Hip bone
A
- Epiphyseal plate b/w 3 bones at the acetabulum
- Ilium: contains the obturator foramen (covered by membrane → gives rise to muscles)
- Ischium: Ischial spine → projected MED may obstruct birth of fetus
- Pubis: G/L Sciatic notch
6
Q
Plane: Tip of coccyx to pubis
A
Ovaries located at this plane
7
Q
Pelvic inlet/outlet shape
A
- Outlet: Diamond shape (narrower in males)
- Divides into urogenital triangle and anal triangle
8
Q
3 different pelvic planes
A
- Narrow pelvic plane (plane of least dimensions): S4 → INF pubis (where head has to pass)
- Tip of coccyx to pubis
- Line of gravity plane: Lumbosacral joint to INF pubis
9
Q
Dimensions of the pelvic cavity size and fetus size
A
- Avg pelvic cavity = 11cm diameter
- Vortex presentation of fetus (Chin twd chest) = 9.5cm diameter
- Brow presentation of fetus (Chin up) = 13.5cm → problematic for child birth
10
Q
Apertures of the pelvis
A
- Pelvic inlet
- ANT sacral foramen
- Obturator canal
- GSF → to LL
- LSF → perineum & gluteal regions
11
Q
How is the pelvis the most important skeleton for forensic identification
A
- Size and shape → male/female
- Transverse ridges and groove present in symphysis of younger adults (teen to late 20s)
12
Q
Mechanical structure of the pelvis
A
- 2 bony arches:
- POS arch → sacrum → acetabulum
- ANT arch → Pubic arch → bear weight in sitting
- Bones organised in trabaculae → resist forces
- Transfer of forces → pelvis acts as struts → allows movement and load transfer
13
Q
Movements affecting the pelvic bone
A
- Stance → weight from trunk to pelvis
- Pelvis wants to tilt further fwd (nutation) ~S2 vertebrae
- But Little movement takes place due to ligaments in the joint of pelvis
- Movement ~ 2-8o
- Occurs from a lying down position to standing position
- Movements increase during late pregnancy (due to relaxin hormone → relax ligaments)
- Complications with POST pregnancy → SI joint pain → ligaments retighten in wrong way
- Refer pain to MED/LOWER buttocks
14
Q
Sacroiliac joint
A
- Synovial ANT
- Fibrous POS
- Held together by strong lig → prevents movement/nutation
15
Q
Ligaments of the sacroiliac joint
A
- Sacroiliac (interosseous)
- Sacrospinous (GSF)
- Sacrotuberous (LSF)
