Bones and Joints of the Pelvis Flashcards
What are the bones that make up the pelvis?
Pair of hip bones together with coccyx
Sacrum in midline posteriorly
What are the joints in the pelvis?
Sacroiliac joints lateral
Synovial joints
Pubic symphysis = secondary cartilaginous joint
What are the three bones making up the hip bone?
Ischium
Ilium
Pubis
What structures in the hip bone do all three fused bones form?
Acetabulum
Obturator foramen
What makes up the ilium superiorly?
Iliac crest
What is the extent of the ilia crest?
Between anterior superior iliac spine anteriorly and posterior superior iliac spine posteriorly
Which surface of the ilium faces posteriorly?
Gluteal
What attaches to the gluteal surface of the ilium?
Gluteal muscles
What is on the anterior aspect of the ilium?
Iliac fossa
What muscle does the iliac fossa give rise to?
Iliacus
Which surface of the ilium is the articular surface for the sacroiliac joint?
Sacral
Which bone of the hip is located anteriorly?
Pubis
What are the components of the pubis?
Body of pubis
Superior and inferior pubic rami
Pubic crest
Pubic tubercle
What forms the pubic symphysis?
Body of pubis on 1 side meeting and articulating with body of pubis on other side in midline
Where is the pubic crest?
Superior aspect of pubis
What does the pubic tubercle do?
Laterally delineates pubic crest
What extends from the pubic tubercle, and where does it go?
Pectineal line
Goes onto superior pubic ramus
What part of the ischium is the attachment for the hamstrings?
Ischial tuberosity
What does the ischial ramus attach to?
Comes forward and continues with inferior pubic ramus
What does the ischial spine demarcate?
Notch above = greater sciatic notch
Notch below = lesser sciatic notch
What is the acetabulum?
Socket of hip joint
What separates the three bones at the acetabulum during development?
Triradiate cartilage
What are the boundaries of the obturator foramen?
Superior and inferior pubic rami
Ischial ramus continuing posteriorly
What makes up the sacrum?
5 fused vertebrae
What forms the lateral masses of the sacrum?
Fused transverse processes
On each side of fused vertebral bodies
What and where is the sacral promontory?
On superior surface have prominent anterior margin
What and where are the alas?
Wing off superior aspect of lateral masses
What does the ala do?
Articulates
- Superiorly with lumbar vertebrae at lumbosacral joint
- Inferiorly with coccyx at sacrococcygeal joint
- Laterally with ilium at sacroiliac joint
What makes up the false or greater pelvis?
Iliac crest
Iliac fossa
What divides the false and true pelvis?
Iliopectineal line
What region of the body is the false pelvis considered to be part of?
Posterior abdominal wall
What is the function of the false pelvis?
Bony protection of abdomen
What is the shape of the true pelvis?
Basin
Where is the perineum?
Beneath pelvic floor but still contained within bony pelvis
What does the true pelvis lie between?
Pelvic inlet and outlet
What is the border of the pelvic inlet?
Starts at superior aspect of pubic symphysis anteriorly Pubic crest laterally Pectineal line of pubic bone Arcuate line of ilium Across sacroiliac joint Anterior margin of ala Anterior margin of sacral promontory
What is the arcuate line?
Delineates iliac fossa and crest above from very lowest part of ilium and ischium below
What makes up the iliopectineal line?
Pectineal line of pubis and arcuate line of ilium
What is the difference in size of the pelvic inlet between males and females?
Usually larger in females
What is the usual shape of the pelvic inlet in females?
Oval
What is the name given to the typical shape of the pelvic inlet in females?
Gynaecoid
What is the typical shape of the male pelvic inlet?
Android = heart shaped
What is the common variant of the male pelvic inlet?
Anthropoid
What is the difference between general structure of the pelvis between males and females?
Male = thick and heavy Female = light and thin
What is the difference between the greater sciatic notch of the pelvis between males and females?
Male = narrow inverted V Female = Almost 90 degrees
What is the difference between the sub-pubic arch of the pelvis between males and females?
Male = acute Female = obtuse
What is the difference between the acetabulum of the pelvis between males and females?
Male = large Female = small
What is the difference between the obturator foramen of the pelvis between males and females?
Male = round Female = oval
What is the difference between the width of the acetabulum compared to the width of the pubic bone between males and females?
In female, distance from acetabulum to pubic symphysis greater than width of acetabulum
In male, about the same
What is the shape of the pelvic outlet?
Diamond
What are the margins of the pelvic outlet?
Inferior aspect of pubic symphysis anteriorly
Tip of coccyx posteriorly
Ischial tuberosities laterally
What is the plane of least dimensions?
Narrowest part of pelvis
What is the shape of the plane of least dimensions?
Almost circular
What does the plane of least dimensions pass through?
S4
Ischial spines
Base of pubic symphysis
What does the head of the baby do during childbirth as it traverses through the pelvis?
Rotates and flexes so it always presents its smallest diameter to part it’s going through
Constantly changing its dimensions to pelvic passage
What type of joints are the sacroiliac joints?
Synovial
What are the sacroiliac joints between?
Ear-shaped/auricular surface of posterior part of sacral ala, and similarly shaped articular surface of ilium
What ligaments hold the sacroiliac joint together?
Sacroiliac ligaments
- Anterior - reinforce capsule
- Posterior - reinforce capsule
- Interosseus - within joint
- Pass between iliac and sacral tuberosities
What happens to the interosseus sacroiliac ligaments as the sacrum rotates?
Tighten > lock joint
What do the accessory ligaments of the sacroiliac joint do?
Further stabilise joint
What are the accessory ligaments of the sacroiliac joint?
Iliolumbar ligaments
Sacrotuberous ligaments
Sacrospinous ligaments
Where are the iliolumbar ligaments?
Between iliac crest and tranverse process of L5
Where are the sacrotuberous ligaments?
Between sacrum and ischial tuberosity
Where are the sacrospinous ligaments?
Between sacrum and ischial spine
What close the sciatic notches into sciatic foramina?
Sacrotuberous and sacrospinous ligaments
What is the nodding movement of the sacrum called?
Nutation (forward)
Counter-nutation (backward)
What happens to the pelvic outlet as the sacrum nutates?
Pushes tip of sacrum out and increases size of pelvic outlet
What happens to the movements of the sacrum during pregnancy?
Hormones of pregnancy increase laxity of ligaments > allows increased movements
What separates the two bones at the pubic symphysis?
Fibrocartilaginous disc separated from bone by intervening hyaline cartilage
What reinforces the pubic symphysis?
Superior and inferior pubic ligaments
Where is the superior pubic ligament?
Goes across to pubic crests and tubercles
Where is the inferior pubic ligament?
An arcuate ligament, arching across either side of inferior aspect of pubic symphysis
Which muscles reinforce the anterior aspect of the pubic symphysis?
Fibres from
- Oblique abdominal muscles
- Rectus sheath
- Adductor longus