pelvis

Osteology

· formed from 3 bones

· fuse in Y-shaped epiphysis in acetabulum

· correct anatomical position

· pubic tubercle and ASIS vertical

· upper border of pubic symphysis and ischial spine horizontal

Lateral surface

Acetabulum

· acetabular notch

· deficient inferior margin

· continues up to medial wall

· continues down to rim of obturator foramen

· filled with transverse ligament

· transverse ligament attaches ligamentum teres

· superior weight-bearing surface

· made up entirely of ilium

· rim attaches labrum

Ilium

· extends above acetabulum anteriorly

· projects forwards as AIIS and ASIS

· curves backward as iliac crest

· thickening 5 cm back is tubercle

· extends above acetabulum posteriorly

· forms greater sciatic notch

· posterior margin above this has PIIS and PSIS

· gluteal surface

· three curved lines

· posterior gluteal ine

· from iliac crest posteriorly above sacral surface to PIIS

· gluteus maximus attaches behind this

· middle gluteal line

· from tubercle of crest to greater sciatic notch

· gluteus medius attaches between posterior and middle lines

· inferior gluteal line

· from ASIS to greater sciatic notch

· gluteus minimus attaches between middle and inferior lines

· ASIS gives rise to

· inguinal ligament above

· sartorius below

· AIIS gives rise to

· straight head of rectus above

· iliofemoral ligament below

· TFL arises from just below iliac crest

· between ASIS and tubercle

· reflected head of rectus arises above upper margin of acetabulum

· behind ASIS

· sacrotuberous ligament arises between PSIS and PIIS

Iliac crest

· posterior ridge along crest

· from PSIS to posterior gluteal line

· in line with transverse tubercles of S3-5

· attaches posterior lamella of lumbar fascia and aponeurosis of latissimus dorsi

· iliocostalis part of erector spinae attaches internal to ridge

· internal to this attaches sacroiliac ligaments

· internal to this is auricular surface of ilium

· quadratus lumborum attaches anterior to ridge

· anterior to this attach

· transversus abdominus to inner lip of crest

· internal oblique to middle of crest

· external oblique to outer lip of crest

· fascia lata attached to whole of outer lip

Pubis

· L-shaped bone

· body projected forward as rami

· superior ramus

· attaches to ilium and ischium at acetabulum

· inferior ramus

· attaches to ischium below obturator foramen

· pubic crest

· upper border of body

· pubic tubercle is lateral prominence on body

· two lines diverge from tubercle along superior ramus

· pectineal line which joins arcuate line of ilium

· obturator crest which passes to obturator notch

· between lines is iliopubic eminence

· on anterior wall of acetabulum

· marks epiphysis

· superior ramus grooved below obturator crest

· obturator sulcus

· lodges obturator nerve and vessels

Attachments to pubis

· pubic crest

· rectus abdominus and pyramidalis

· pectineal line

· conjoint tendon and lacunar ligament medially

· pectineal ligament laterally

· pubic tubercle

· inguinal ligament

· pectineus attached

· between pectineal line and obturator crest

· anterior body

· adductor longus tendon

· inferior ramus

· gracilis (from edge)

· adductor brevis (between behind adductor longus)

· adductor magnus (between behind adductor brevis)

· obturator externus (from obturator margin)

Ischium

· L-shaped bone

· vertical body joins ilium

· projected forward as ramus

· behind acetabulum

· low elevation at line of fusion of ilium and ischium

· ischiofemoral ligament arises near rim of acetabulum

· ischium completes greater sciatic notch medially

· sciatic nerve lies on ischium

· spine of ischium projects medially

· separates greater and lesser sciatic notch

· pudendal n lies medial to spine

· internal pudendal vessels cross tip

· nerve to obturator internus lies on spine

· greater sciatic notch

· sacrospinous ligament attached from spine to sacrum

· converts greater sciatic notch into foramen

· transmits piriformis and sciatic nerve

· lesser sciatic notch

· sacrotuberous ligament attached from sacrum to ischial tuberosity

· converts lesser sciatic notch into foramen with sacrospinous ligament

· transmits obturator internus

· superior gamellus originates from spine above notch

· inferior gamellus originates from tuberosity below notch

· ischial tuberosity

· divided into upper smooth half and lower rough half by transverse ridge

· smooth area divided by vertical ridge

· semimembranosus attaches to lateral smooth area

· semitendinosus and long head of biceps femoris attach to medial smooth area

· rough area separated by longitudinal crest

· adductor magnus arises from lateral rough surface

· adductor magnus origin continues forward onto inferior ramus

· sacrotuberous ligament attaches to medial rough surface

· obturator foramen

· superior obturator sulcus for obturator nerve and artery

· obturator membrane arises from margin except superiorly

· obturator externus arises from outer surface of membrane and bony margins

Arthrology

joints

Sacroiliac joint

· synovial joint between auricular surfaces of ilium and sacrum

· atypical synovial joint

· lined by fibrocartilage

· obliterated by fibrous bands

· surfaces jagged

· very little movement

Capsule

· arises from articular margins

· reinforced by SI ligaments

· ventral

· strong interosseous

· dorsal

· posterior rami pass between interosseous and dorsal ligaments

Ligaments

Sacrotuberous

· attached to

· posterior border of ilium between PSIS and PIIS

· transverse tubercles of sacrum below auricular surface

· passes to medial surface of ischial tuberosity

· upper edge attached to curved ridge of bone

· called falciform process

· is degerated tendon of long head of biceps

· attaches gluteus maximus

Sacrospinous

· lies deep to sacrotuberous ligament

· attached to lower sacrum and upper coccyx

· passes to spine of ischium

Iliolumbar

· sideways V

· apex attached to TP of L5

· upper band passes to iliac crest

· gives origin to QL

· becomes continuous with lumbar fascia

· lower band to SI jt

· called lumbosacral ligament

Stability

· depends entirely on ligaments

· no bony factors

· irregular surfaces depend on apposition by ligaments

· body weight tends to separate joint

Sacrococcygeal joint

· between sacrum and coccyx

· symphysis (secondary cartilagenous joint)

· ends covered by hyaline cartilage

· intervening fibrocartilaginous disc

· reinforced by SC ligaments

· ventral

· 2 dorsal

· 2 lateral (may ossify)

Pubic symphysis

· symphysis (secondary cartilagenous joint)

· ends covered by hyaline cartilage

· intervening fibrous bands

· may be central fluid space

· reinforced by

· superior pubic ligament above

· arcuate pubic ligament below