Pelvic Girdle Anatomy

• The pelvic girdle is a bony structure connecting the lower limbs to the axial skeleton.

Pelvic Girdle Function

• Transfers weight from the upper body to the lower limbs.
• Provides attachment for powerful muscles involved in locomotion and posture.
• Supports and protects the pelvic organs.

Pelvic Girdle Components

• The pelvic girdle consists of two hip bones, also known as coxal or innominate bones.
• The sacrum and coccyx, parts of the vertebral column, connect to the hip bones and contribute to the pelvis's posterior wall.

Hip Bone Formation

• Each hip bone forms from the fusion of the ilium, ischium, and pubis.
• These bones are separate during childhood, fusing between the ages of 15 and 23.
• Fusion occurs in the acetabulum, a cup-shaped socket on the hip bone's lateral side that articulates with the femur's head.

Ilium

• The ilium is the largest and most superior of the three bones that fuse, contributing to the acetabulum's superior part.
• Features of the ilium:
  • Iliac crest: Superior border, palpable through the skin.
  • Anterior superior iliac spine (ASIS): Prominent projection at the iliac crest's anterior end.
  • Anterior inferior iliac spine (AIIS): Located inferior to the ASIS, serving as the rectus femoris muscle's attachment point.
  • Posterior superior iliac spine (PSIS): Located at the posterior end of the iliac crest.
  • Posterior inferior iliac spine (PIIS): Located inferior to the PSIS.
  • Greater sciatic notch: Large notch on the posterior border of the ilium and ischium, converted into a foramen by the sacrospinous ligament.
  • Iliac fossa: Large, concave surface on the medial side of the ilium.
  • Auricular surface: Ear-shaped surface articulating with the sacrum at the sacroiliac joint on the medial side.

Ischium

• The ischium forms the hip bone's posteroinferior part.
• The ischium contributes to the acetabulum's posterior part.
• Features of the ischium include:
  • Ischial tuberosity: Large, blunt projection bearing the body's weight when sitting.
  • Ischial spine: Pointed projection superior to the ischial tuberosity, separating the greater sciatic notch from the lesser sciatic notch.
  • Lesser sciatic notch: Located inferior to the ischial spine.
  • Ramus of the ischium: Extends anteriorly to join the inferior pubic ramus.

Pubis

• The pubis forms the anterior part of the hip bone.
• It contributes to the acetabulum's anterior part.
• Features of the pubis include:
  • Superior pubic ramus: Extends from the acetabulum to the pubic body.
  • Inferior pubic ramus: Extends from the pubic body, joining the ischial ramus.
  • Pubic body: Medial part of the pubis articulating with the opposite pubic body at the pubic symphysis.
  • Pubic crest: Thickened ridge on the superior part of the pubic body.
  • Pubic tubercle: Lateral projection on the pubic crest, serving as the inguinal ligament's attachment point.
  • Obturator foramen: Large opening in the hip bone, formed by the ischium and pubis, largely closed by the obturator membrane.

Acetabulum

• The acetabulum is a deep, cup-shaped socket on the hip bone's lateral aspect.
• The ilium, ischium, and pubis fuse to form it.
• It articulates with the femur's head, forming the hip joint.
• The acetabular labrum, a fibrocartilaginous rim, deepens the acetabulum and increases the hip joint's stability.

Pelvic Brim

• The pelvic brim (pelvic inlet or linea terminalis) is a continuous oval ridge separating the true pelvis from the false pelvis.
• It is formed by the sacral promontory, ala of the sacrum, arcuate line of the ilium, pectineal line of the pubis, and pubic crest.

True and False Pelvis

• The false pelvis (greater pelvis) is superior to the pelvic brim and is part of the abdomen.
• It contains abdominal organs like the small intestine and sigmoid colon.
• The true pelvis (lesser pelvis) is inferior to the pelvic brim, surrounding the pelvic cavity.
• It contains pelvic organs such as the urinary bladder, rectum, and internal reproductive organs.

Pelvic Outlet

• The pelvic outlet is the true pelvis's inferior opening.
• It is bounded by the pubic arch, ischial tuberosities, sacrotuberous ligaments, and coccyx.

Pelvic Ligaments

• Several strong ligaments support the pelvic girdle and sacroiliac joint.
• Sacroiliac ligaments connect the sacrum to the ilium.
• Sacrospinous ligament connects the sacrum to the ischial spine.
• Sacrotuberous ligament connects the sacrum to the ischial tuberosity.
• The pubic symphysis is a cartilaginous joint between the pubic bones reinforced by ligaments.

Pelvic Musculature

• Muscles attached to the pelvic girdle are essential for movement and stability.
• Muscles include:
  • Hip flexors: Iliopsoas, rectus femoris, sartorius.
  • Hip extensors: Gluteus maximus, hamstrings (biceps femoris, semitendinosus, semimembranosus).
  • Hip abductors: Gluteus medius, gluteus minimus, tensor fasciae latae.
  • Hip adductors: Adductor longus, adductor brevis, adductor magnus, gracilis, pectineus.
  • Pelvic floor muscles support the pelvic organs and control continence.

Clinical Significance

• Pelvic fractures: Often result from high-energy trauma, potentially causing significant bleeding and injury to pelvic organs.
• Hip dysplasia: Abnormal hip joint development, leading to instability and potential dislocation.
• Sciatica: Compression or irritation of the sciatic nerve, often from a herniated disc or piriformis syndrome.
• Pelvic inflammatory disease (PID): Infection of the female reproductive organs, frequently caused by sexually transmitted infections.
• Osteitis pubis: Inflammation of the pubic symphysis, common in athletes.

Sexual Dimorphism

• Male and female pelves show significant differences related to childbearing.
• Female pelvis:
  • Wider and shallower.
  • Larger pelvic inlet and outlet.
  • Subpubic angle wider than 80 degrees.
  • Less curved sacrum.
  • Lighter and thinner bones.
• Male pelvis:
  • Narrower and deeper.
  • Smaller pelvic inlet and outlet.
  • Subpubic angle less than 70 degrees.
  • More curved sacrum.
  • Heavier and thicker bones.