Pelvic girdle, cavity & neurovascular structure

• Pelvic girdle


  The basin-shaped ring of bones connecting the vertebral column to the femurs

  
• Pelvic girdle


  • Forms part of the appendicular skeleton of the lower limb
  • Transmits the weight of the upper body to the lower limbs via the sacroiliac joints
• Bones of the pelvic girdle

  • Right and left hip bones (os coxae)
  • Sacrum
  • Coccyx

  
• Os coxae (hip bone)


  Large, irregular bones that each develop from the fusion of 3 bones: the ilium, ischium and pubis

  
• Acetabulum


  1. Laterally facing, hemispherical hollow that forms the socket of the hip and articulates with the head of the femur

  2. It has contributions from all three coxal elements: ilium, ischium, and pubis

  
• Ilium


  • Superior, fan-shaped part of the hip bone
  • Ala- represents the spread of the fan
  • Body- handle of the fan
  • Iliac crest- rim of the fan
  • Iliac fossa- anteromedial concave surface of the ala
  • Sacropelvic surface- dorsal portion of the internal surface of the ala facing the sacrum

  
• Ischium


  • Body- helps form the acetabulum
  • Ramus- forms part of the obturator foramen
  • Obturator foramen- large foramen encircled by the two pubic rami and the ischium
  • Ischial tuberosity- blunt, rough, and massive posteroinferior corner of the os coxae
  • Ischial spine- small pointed posteromedial projection near the junction of the ramus and body just inferior to the greater sciatic notch
  • Lesser sciatic tuberosity- concavity between the ischial spine and the ischial tuberosity

  
• Pubis


  • Anteroinferior portion of the bone that approaches the opposite os coxae at the midline
  • Superior ramus- helps form the acetabulum
  • Inferior ramus- contributes to the border of the obturator foramen
  • Pubic crest- thickening on its anterior part that connects the pubic tubercle to the pubic symphysis
  • Pubic tubercle- lateral ending of the pubic crest as a prominent swelling
  • Pecten pubis- Lateral part of the superior pubic ramus that is an oblique ridge

  
• Sacrum


  • Sacral canal- continuation of the vertebral canal in the sacrum
  • Sacral foramina- 4 pairs each on the anterior and posterior surfaces for the exit of the anterior and posterior rami of the spinal nerves
  • Sacral promontory- anterior projecting edge of the body of S1
  • Apex- tapering inferior end of the sacrum with an oval facet for articulation with the coccyx
  • Sacral hiatus- results from the absence of laminae and spinous process of S5
  • Sacral cornua- inferior articular processes of S5 vertebra projecting inferiorly on each side of the sacral hiatus
• Sex differences in pelvic girdle

  • Differences linked to function: Pregnancy and childbirth in females, Heavier build and larger muscles of men
• Pubic arch


  Formed by the right and left ischiopubic rami which meet at the pubic symphysis

  
• Subpubic angle


  Inferior borders of pubic arch, the width of which is determined by the distance between the right and the left ischial tuberosities
• Sacroiliac joints


  • Atypical synovial joint with limited movement
  • Compound joint composing of an anterior synovial joint between the auricular surfaces of the sacrum and ilium, and a posterior syndesmosis- fibrous joint between the tuberosities of the sacrum and the ilium
• Ligaments of the sacroiliac joints

  • Anterior sacroiliac ligaments
  • Interosseous sacroiliac ligaments
  • Posterior sacroiliac ligaments
  • Sacrotuberous ligaments
  • Sacrospinous ligaments
• Sacroiliac ligaments


  Stabilise the sacroiliac joint
• Contents of the obturator canal


  • Obturator nerve and vessels
• Contents of the lesser sciatic foramen

  • Pudendal nerve
  • Internal pudendal vessels
  • Nerve to obturator internus
• Contents of the greater sciatic foramen

  • Above piriformis: Superior gluteal nerves and vessels
  • Below piriformis: Inferior gluteal nerves and vessels, Sciatic nerve, Pudendal nerve, Internal pudendal vessels, Posterior femoral cutaneous nerves, Nerve to the obturator internus, Nerve to quadratus femoris muscles
• Pubic symphysis


  Secondary cartilaginous joint that unites the bodies of the pubic bones in the median plane

  
• Ligaments of the pubic symphysis

  • Superior pubic ligaments
  • Inferior (arcuate) pubic ligaments
• Lumbosacral joints


  3 articulations between L5 and S1: Anterior intervertebral joint formed by L5/S1 IV disc, 2 posterior zygapophysial joints (facet joints)

  
• Iliolumbar ligaments


  • Fan-like ligaments radiating from the transverse processes of L5 to the iliac crests, Strengthens lumbosacral joints, Accessory to the posterior and interosseus sacroiliac ligaments
• Sacrococcygeal joint


  Secondary cartilaginous joint with an IV disc, Fibrocartilage and ligaments join the apex of the sacrum to the base of the coccyx

  
• Pelvic types


  • Gynecoid and anthroid is common in white females
  • Gynecoid and anthropoid is common in black females
  • Anthroid is common in males
  • Platypelloid is not common in either sex
• Pelvic measurements


  Used to determine the capacity of the female pelvis for childbearing
• Pelvic measurements


  • True conjugate diameter
  • Transverse diameter
  • Oblique diameter
• True conjugate diameter


  From the superior border of the pubic symphysis to the sacral promontory, ~1.5 cm shorter than diagonal conjugate that is measurable in life

  
• Pelvic cavity


  Funnel-shaped, bounded superiorly by the pelvic inlet and inferior abdominal cavity, inferiorly by the pelvic floor, anteriorly by the pubic bones and pubic symphysis, posteriorly by the sacrum, coccyx and adjacent ilia, and laterally by the os coxae and obturator foramen
• Greater (false) pelvis


  Superior to the pelvic inlet, between the iliac fossa, occupied by abdominal viscera

  
• Lesser (true) pelvis


  Between the pelvic inlet and outlet, contains the pelvic viscera
• Muscles of the pelvic walls and floor

  • Obturator internus
  • Proximal attachment, Distal attachment, Innervation, Main action
• Boundaries of the pelvic outlet

  • Anterolaterally- pubic symphysis and ischiopubic rami
  • Laterally- ischial tuberosities
  • Posterolaterally- inferior margin of the sacrotuberous ligament
  • Posteriorly- tip of the coccyx

  
• Greater (false) pelvis


  • Superior to the pelvic inlet
  • Between the iliac fossa
  • Occupied by abdominal viscera (Ileum, sigmoid colon, etc.)

  
• Lesser (true) pelvis


  • Between the pelvic inlet and outlet
  • Contains the pelvic viscera

  
• The pelvic cavity has an antero-inferior wall, 2 lateral walls, a posterior wall and a floor
• Obturator internus


  • Proximal attachment: Pelvic surfaces of ilium and ischium
  • Distal attachment: Greater trochanter of the femur
  • Innervation: Nerve to obturator internus (L5,S1, S2)
  • Main action: Laterally rotates thigh, Holds head of femur in acetabulum

  
• Piriformis


  • Proximal attachment: Pelvic surface of S2-S4
  • Distal attachment: Greater trochanter of the femur
  • Innervation: Anterior rami of S1&S2
  • Main action: Laterally rotates thigh, Abducts thigh, Holds head of femur in acetabulum

  
• Coccygeus (ischiococcygeus)


  • Proximal attachment: Ischial spine
  • Distal attachment: Inferior end of sacrum and coccyx
  • Innervation: Br. of S4&S5
  • Main action: Flexes coccyx

  
• Levator ani


  • Proximal attachment: Body of pubis, Tendinous arch of obturator fascia, Ischial spine
  • Distal attachment: Perineal body, Coccyx, Walls of the prostate/vagina, rectum and anal canal
  • Innervation: Nerve to levator ani (br. of S4), Inferior anal n., Coccygeal plexus
  • Main action: Resists increase in intra-abdominal pressure
• The antero-inferior pelvic wall is weight-bearing, formed by the bodies and rami of the pubic bones and the pubic symphysis, and participates in bearing the weight of the urinary bladder