Pelvic Girdle (2)-1

Chapter 17: Pelvic Girdle

Structure of the Pelvis

• Pelvic Girdle (Pelvis)

  • Comprises four bones:

    • Sacrum

    • Coccyx

    • Two Ilium (hip bones)

  • Joints:

    • Posterolaterally: 2 Sacroiliac (Left & Right)

    • Anteriorly: Symphysis Pubis

    • Superiorly: Lumbosacral joint

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Functions of the Pelvis

• Supports body weight.

• Receives ground forces.

• Provides protection for pelvic viscera.

• Provides attachment for muscles.

• Forms the bony portion of the birth canal.

False Pelvis

• False Pelvis (Greater/Major Pelvis)

  • Bony area between iliac crests, superior to the pelvic inlet.

  • Contains no pelvic organs.

  • Pelvic Inlet: imaginary line between sacral promontory (posterior) and superior border of symphysis pubis (anterior).

True Pelvis

• True Pelvis (Lesser/Minor Pelvis)

  • Lies between pelvic inlet and pelvic outlet.

  • Forms the Pelvic Cavity:

    • Contains parts of the GI tract, urinary tract, and some reproductive organs.

    • Forms the birth canal in females.

Differences between Male and Female Pelvis

• Pelvic Cavity Opening:

  • Males: heart-shaped.

  • Females: oval.

  • Pelvic Cavity Shape:

    • Males: longer, funnel-shaped.

    • Females: shorter, less funnel-shaped.

Sacrum Variations

• Sacrum Shape:

  • Females: shorter, less curved, tilted backward.

  • Males: longer, more curved, tilted forward.

Wall and Arch Differences

• Walls, Acetabula, and Ischial Tuberosities:

  • Females: broader walls, further apart acetabula, and ischial tuberosities.

  • Males: narrower walls.

• Pelvic Arch:

  • Wider and more rounded in females.

Sacroiliac Joint

• Joint Structure:

  • Irregular ridges and two surfaces:

    • Concave (sacrum) and convex (ilium).

• Functions:

  • Transmits weight from upper body through the vertebral column to hips.

  • Designed for stability with minimal mobility.

Joint Motion and Types

• Accepted Motions:

  • Nutation (Sacral Flexion):

    • Sacral promontory rotates anterior/inferior, increasing pelvic outlet.

  • Counternutation (Sacral Extension):

    • Sacral promontory rotates posterior/superior, increasing pelvic inlet.

LAB: SI Bones and Landmarks

• Sacrum Anatomy:

  • Base, promontory, superior articular processes, ala, foramina, auricular surface, pelvic surface.

• Ilium Anatomy:

  • Tuberosity, auricular surface, iliac crest, spinous processes (anterior and posterior), greater sciatic notch and foramen.

• Ischium and Pubis Anatomy:

  • Ischial body, ramus, tuberosity, superior/inferior pubic rami, obturator foramen.

Pubic Symphysis

• Location & Structure:

  • Midline joint between right and left pubic bones, with a fibrocartilage disk.

  • Amphiarthrodial joint, offering limited movement.

• Stabilizing Ligaments:

  • Superior Pubic Ligament:

    • Attaches pubic tubercles, strengthens joint.

  • Inferior Pubic Ligament:

    • Attaches inferior rami, reinforces joint structure.

Lumbosacral Joint

• Components:

  • 5th Lumbar Vertebra, 1st Sacral Vertebra, IV Disc.

• Supporting Ligaments:

  • Supraspinal, interspinal ligaments, and previously mentioned iliolumbar and lumbosacral ligaments.

Lumbosacral Angle

• Determination:

  • Draw line parallel to the ground and along the sacrum's base. Optimal angle is 30 degrees.

• Influences on Movement:

  • Increased lordosis causes shearing stresses of L5 on S1.

Sagittal Plane: Pelvic Girdle Motions

• Motions:

  • Neutral pelvis: ASIS aligned with Pubic Symphysis.

  • Tilts:

    • Anterior: ASIS moves anterior to PS.

    • Posterior: ASIS moves posterior to PS.

Control of Pelvic Motions

• Muscle Controls:

  • Anterior tilt involves spine extensors and hip flexors.

  • Posterior tilt involves trunk flexors and hip extensors.

  • Lateral tilt controlled by trunk lateral benders and hip abductors.

Transverse Plane Pelvic Rotation

• Pelvic Rotation:

  • Anatomical position: ASIS in same plane.

  • Forward Rotation:

    • R pelvis moves forward; involves medial rotation.

  • Backward Rotation:

    • R pelvis moves backward; involves lateral rotation.

  • Point of Reference:

    • Unsupporting side determines rotational direction.