Pelvis as a Ring: Bony Pelvis, Male and Female Differences

Question 1

Give examples of anatomical rings in the body and what do they have in common

Answer 1

• Pelvis
• Ankle joint
• Occular orbit
• All have a structural design that can give rise to medical emergencies

Question 2

What is the significance of the ring structure

Answer 2

• Injuries caused by high energy forces in one area will correspond to a bone or lesion on the opposite side
• It is a basic design flaw, exceptions are low energy insufficiency fractures (e.g. osteoporotic patients)

Question 3

Name 2 examples of anatomical ring fractures

Answer 3

• Pott’s fracture - ankle joint
• Blow-out fracture - The ocular orbit

Question 4

What bones make up the bony pelvis

Answer 4

• Right innominate bone
• Left innominate bone
• Sacrum

Question 5

What are the bones of the Pelvis reinforced by

Answer 5

• Joints of the bony assembly
• Ligaments if the joints

Question 6

What joints make up the pelvic ring

Answer 6

• Sacroiliac joints
• Pubic symphysis (secondary cartilaginous joint)

Question 7

What ligaments make up the pelvic ring

Answer 7

• Anterior pelvic ligaments (symphyseal ligaments) - surround pubis
• Posterior pelvic ligaments - surround sacrum

Question 8

What ligaments make up the group known as the anterior pubic ligaments

Answer 8

-Superior pubic ligament
- Arcuate pubic ligament (also known as the arcuate ligament, most important)
- Anterior pubic ligament
- Posterior pubic ligament

Question 9

What do the anterior pelvic ligaments do

Answer 9

• Resist external rotation
• Resist shear and flexion

Question 10

What are the posterior ligaments also known as

Answer 10

• Sacroiliac complex
• Posterior tension band

Question 11

What ligaments make up the posterior ligaments

Answer 11

• Interosseous sacroiliac ligament
• Posterior sacroiliac ligament
• Iliolumbar ligament

Question 12

What do the posterior pelvic ligaments do

Answer 12

• Resist anterior-posterior translation of the pelvis
• They resist cephalad-caudad displacement of pelvis
• Resist rotation and augment posterior SI ligaments

Question 13

Which 2 ligaments contribute to the pelvic floor

Answer 13

• Sacrospinous ligaments
• Sacrotuberous ligaments

Question 14

What is the significance of the sacrum in the pelvic ring

Answer 14

• Between 2 iliac bones
• Secured bilaterally by sacroiliac joints
• Subject to pressure from spine above and the weight of the lower limbs below

Question 15

What are the 3 types of pelvic ring injuries

Answer 15

• Anterior posterior compression
• Lateral compression
• Vertical shear

Question 16

What is corona mortis

Answer 16

• The anastomosis of the arterial and venous systems of the external iliac and obturator systems

Question 17

At what level does the abdominal aorta bifurcate to become the left and right common iliac arteries

Answer 17

• L4/L5
• Then branches again into what will become the internal and external iliac arteries

Question 18

Describe the branching of the internal and external iliac in the pelvic region and what vessels they become

Answer 18

• External iliac artery travels anteriorly along the pelvic brim and emerges as the common femoral artery distal to the inguinal ligament.
• Internal iliac artery dives posteriorly near the sacroiliac joint and divides into anterior (becomes obturator artery which has an anastomoses with the external iliac system) and posterior (becomes superior gluteal artery) divisions.

Question 19

What is Corona Mortis (Crown of death)

Answer 19

• Corona Mortis is a connection (anastomoses) between the obturator and external iliac systems.
• Forms a ring (crown) - problem because a lesion here will cause significant bleeding and death

Question 20

What neurological structures are vulnerable in the pelvis and why

Answer 20

• Lumbosacral trunk as it crosses the anterior sacral ala and sacroiliac joint.
• L5 nerve root as it exits below L5 and travels over the sacral ala medial to the Sacroiliac joint
• Superior hypogastric plexus and the hypogastric nerve as they are found close to the sacroiliac joint