Pelvic Girdle and Sacrum

Coxal Bones

bound to the sacrum posteriorly along the SI joint by ligamentous and muscular connection; consists of 3 separate bones in early life before they fuse together in adulthood; large hip bone (pelvic bone) attached to the sacrum and the coccyx- attaches legs to axial skeleton

what are the 3 bones that make up the coxal bones

ilium, ischium, pubis

what are the ischium and pubis called together

the oxcoxa

ilium

the largest and most uppermost coxal bone; upper, flaring portion of pelvis

iliac crest

upper, curving boundary of ilium extending from ASIS to PSIS

ischium

the strongest and lowermost coxal bone; lower, posterior portion of pelvic (sit bones)

pubis

the most anteriorly placed coxal bone; medial, anterior portion

pelvic inlet

divides the pelvis into two parts

pelvic outlet

where the digestive tract and female reproductive tract pass through; often just large enough for childbirth; can expand during delivery due to increased flexibility of the pubic symphysis

false pelvis

above the pelvic brim, the flaring region of the hip bones

true pelvis

below the pelvic brim; where the organs of the reproductive tract reside

acetabulum

the hip socket, formed by union of ilium, ischium and pubis; where the head of the femur articulates with the pelvis

femoroacetabular impingement (FAI)

bony overgrowth of acetabulum or femoral head; often asymptomatic and does not always require intervention; classified as CAM or Pincer or both

anterior superior iliac spine (ASIS)

prominent projection at anterior end of iliac crest (hip point)

insertion of sartorius and tensor fascia latae (TFL)

anterior inferior iliac spine

less prominent projection short distance below ASIS

insertion for rectus femoris which is a hip flexor

posterior superior iliac spine (PSIS)

posterior end of iliac crest

insertion for glute max, posterior SI ligament

posterior inferior iliac spine

just below the PSIS

insertion for posterior sacroiliac ligaments

iliac fossa

bowl shaped inner surface of the ilium

iliopectineal line

curved line running along the ilium and pubis dividing the false and true pelvis

pubis

located anteriorly; abdominal muscles attach to the pubis to allow for trunk flection

greater sciatic notch

large notch just below posterior inferior spine

lesser sciatic notch

smaller notch just below the ischial tuberosity

ischial tuberosity

large, rough process on inferior ischium; major site of attachment for hamstring muscles and the sacrotuberous ligament; majorly supports your weight when you sit but also is an important site for hamstring attachment

sacrospinous ligament

attaches the ischial spine to the sacrum

lschial spine

pointed projection just above the tuberosity; attachement for sacrospinous ligament

pubic symphysis

cartilaginous amphiarthrotic joint between the pubic bones

superior pubic ramus

part of pubis between symphysis and acetabulum, forms top of obturator foramen

inferior pubic ramus

part of pubis extending down from the symphysis, unites with the ischium

ischial ramus

part of ischium anterior to the ischial tuberosity

ramus

projection from a body outward

foramen

big hole in the bone

pubic arch

curve formed by two inferior pubic rami

subpubic angle

angle formed by inferior pubic rami larger in women than in men

pubic crest

upper margin of superior ramus, most superior portion of the pubic bone

pubic tubercle

rounded process at end of the crest

important attachment point for abdominal musculature

obturator foramen

large hole in the anterior surface; largest foramen in the body

pelvic inlet

boundary into the true pelvis, formed by pubic crests, iliopectineal lines and sacral promontory

sacrum

made of 5 separate vertebrae until approximately 25 years of age and then fused to form one wedge- shaped bone; strong attachment point for gluteal muscles

sacral promontory

protuberance from the anterior, upper border of the sacrum into the pelvis; size limits anterior posterior diameter or pelvic inlet in obstetrics

larger sacral promontory leads to

smaller pelvic inlet

sacral canal

inferior part of the vertebral canal

anterior (sacral) foramina

pairs of holes along anterior surface for passage of spinal nerves

posterior (sacral) foramina

pairs of holes along posterior surface for passage of spinal nerves

sacral hiatus

gap in posteriro wall in bottom segment; an epidural will be inserted here in children

superior articular facet

where the vertebrae interact with each other in sliding joints; flat joint surface on each side of superior entrance to sacral canal

medial sacral crest

bumpy ridge along middle of posterior surface, similar to spinous processes

intermediate sacral crest

bumpy ridge just lateral to posterior foramina

lateral sacral crest

bumpy ridge just lateral to posterior foramina

apex

inferior tip of sacrum

auricular surface

ear-shaped surfaces articulating with the ilium

what are sacral crests for

the attachment of muscles