What is the pelvis made up of?
What are the categories of bones in the pelvis?
- Innominate bones
What do the 2 innominate bones of the pelvis form?
The iliac crest
Where do the 2 innominate bones of the pelvis join?
At the sacrum and the coccyx
What is formed when the two innominate bones of the pelvis join at the sacrum and the coccyx?
The pelvic girdle
What does the linea terminalis define?
Where you enter the pelvis from the faux pelvis
What does the linea terminalis consist of?
- Arcuate line
- Pectineal line
- Pubic crest
What osteological features do the innominate bones of the pelvis have?
- Ischial spine
- Ischial tuberosity
What does the ischial spine seperate into?
The greater and lesser sciatic notches
What is the function of the ischial tuberosity?
It is the part of the pelvic girdle on which you sit
What is the gynacological importance of the sacrum?
The anterior superior edge of the first sacral vertebrae is very prominent, and projects into the pelvic cavity, which can be a problem when giving birth
What is the 'false pelvis'?
The greater pelvis, superior to the linea terminalis
Does the false pelvis have any gynacological relevance?
What is the 'true pelvis'?
The lesser pelvis, a bony canal that is solid and immobile
What is a 'good' pelvis for childbirth termed?
A gynacoid pelvis
What are the features of a gyancoid pelvis?
- Round inlet
- Straight side walls
- Ischial spines not too prominent
- Well rounded sciatic notch
- Sub-pubic arch greater than 90 degrees
What are the 'pelvic planes' of the pelvis?
- Pelvic inlet
- Plane of greater diameter
- Plane of least diameter
- Pelvic outlet
What does a clinical assessment of the pelvis consist of?
- Measuring the anteroposterior diameter of the pelvic inlet
- Assessing the mid-pelvis
- Assessing the pelvic outlet
How is the obstetric conjugate measured?
From the sacral promontory to the midpoint of the pubis symphysis
What does the obstetric conjugate define?
The minimum AP diameter
What is the problem with the measurement of the anteroposterior diameter?
It cannot be palpated, so must make an approximation using the diagonal conjugate
How is the diagonal conjugate measured?
From the sacral promontory to the inferior border of the pubic symphysis
How does the diagonal conjugate measurement compare to the obstetric conjugate?
It is slightly smaller
How is the mid-pelvis assessed?
- Check for straight side walls
- Bispinous diameter
What is meant by the bispinous diameter?
Distance between the ischial spines
How is the pelvic outlet assessed?
- Infrapubic angle
- Distance bewteen the ischial tuberosity
How are the ligaments of the pelvis involved in delivery?
They provide some 'give' in delivery
What are the ligaments of the pelvis?
- Sacrospinous ligament
- Sacrotuberous ligament
Where does the sacrospinous ligament run?
Sacrum to ischial spine
Where does the sacrotuberous ligament run?
Sacrum to ischial tuberosity
What happens to the ligaments during pregnancy?
Hormones serve to soften the ligament, to make them more stretchy and soften joints