Applied anatomy of the pelvis

Question 1

What is the false pelvis?

Answer 1

Area bound by the ala of the ilium superior to the ilio-pectineal line (part of abdominal cavity).

Question 2

What is the true pelvis?

Answer 2

Cavity below the ilio-pectinate line.

Question 3

What are the boundaries of the true pelvis?

Answer 3

• Sacrum (posterior)
• Pubic bone (anterior)
• Inner surface of ischium and ilium (lateral)

Question 4

What are the functions of the pectoral girdle?

Answer 4

1. Transmission of weight to legs
2. Closure of lower boundary of abdominal cavity
3. Forms skeletal framework of birth canal (females)
4. Attachment for back, abdominal and lower limb muscles

Question 5

Where is weight transferred to in standing and sitting positions?

Answer 5

• Standing: Roof of the acetabulum
• Sitting: Ischial tuberosities

Question 6

How is the hip bone adapted to weight-bearing?

Answer 6

The bone along the lines of weight transmission is especially thickened.

Question 7

What type joint is the sacro-iliac joint?

Answer 7

Synovial joint

Question 8

What is the significance of downwards force on sacrum?

Answer 8

It is driven to rotate anteriorly about the axis of S2.

Question 9

What structures resist the rotation of the sacrum in weight-bearing?

Answer 9

• Upwards displacement:
  1. Sacrospinous ligament
  2. Sacrotuberous ligament
• Forward displacement:
  1. Sacro-iliac joint (sacrum is wedge-shaped, interlocking ridges between sacrum and ilium)
  2. Interosseus sacroiliac ligament

Question 10

What sturctures in the pelvis support the pelvic structures?

Answer 10

• Pelvic diaphragm (levator ani, coccygeus)
• Inward projection of ischial spine and coccyx

Question 11

What are the structures supported by the pelvic floor?

Answer 11

• Bladder
• Rectum
• Uterus (females)

Question 12

What are the differences between the male and female pelvis?

Answer 12

1. The female pelvis has obtuse pelvic incisura while the male pelvis has acute pelvic incisura
2. Female sacrum is straight and wider while male sacrum is curved and narrower
3. Female pelvic inlet is wider than male pelvic inlet
4. Female pubic ramus is wider (> acetabulum) than the male pubic ramus (< acetabulum)
5. Female sciatic notch is wider than male
6. Female ischial spine is smaller and less inverted than male

Question 13

What is the reason for male-female differences in pelvic structure?

Answer 13

• Male: Stability
• Female: Childbirth

Question 14

What is the longest dimension of the female pelvic inlet?

Answer 14

Transverse

Question 15

What is the longest dimension of the female pelvic outlet?

Answer 15

Antero-posterior

Question 16

What is the consequence of the dimensions of the pelvic inlet/outlet for birth?

Answer 16

The baby needs to rotate by 90° in the birth canal during birth (first facing laterally and then posteriorly).

Question 17

What is the constraint of bipedalism on the shape of the pelvis?

Answer 17

The sacral promontory and hip joint should be in the same vertical plane when upright. This means pelvis is flattened antero-posteriorly.

Question 18

What are the different types of female pelvis?

Answer 18

1. Gynaecoid (50%)
2. Anthropoid (25%)
3. Android (20%)
4. Platypelloid (5%)

Question 19

What is the peritoneum relationship of the rectum?

Answer 19

• Upper 1/3: Covered anteriorly and lateraly by peritoneum
• Middle 1/3: Covered anteriorly by peritoneum
• Lower 1/3: Retroperitoneal

Question 20

What is a hysterosalpingogram?

Answer 20

Dye is injected into the uterus and x-ray is taken to see whether the fallopian tubes are patent.

Question 21

When does the bladder istend above pelvic inlet?

Answer 21

• Prostatic enlargement (men)
• Pregancy (women)
• Children

Question 22

What is an anteflexed uterus?

Answer 22

The cervical canal is ~90° to the vaginal canal.

Question 23

What is an antiverted uterus?

Answer 23

The body of the uterus tilts anteriorly from the cervix.