Pelvic and Hip Anatomy Overview

Overview

This lecture reviews the anatomy of the pelvis and hip, key landmarks, differences between male and female pelvis, and radiographic procedures and positioning for imaging the pelvis and hip.

Pelvic and Hip Anatomy

• The pelvis consists of two hip bones, the sacrum, and the coccyx.
• The pelvic girdle is made of two hip (innominate or os coxae) bones.
• Each hip bone is composed of the ilium, ischium, and pubis, which fuse in adulthood.
• The pelvis is divided into iliopubic and ilioischial columns to identify acetabular fractures.
• The ilium has a body (superior 2/5 of acetabulum) and ala, with four spines (ASIS, AIIS, PSIS, PIIS).
• The iliac crest runs from ASIS to PSIS; the iliac fossa is on the medial ala.
• The arcuate line separates the iliac fossa from the body; the auricular surface articulates with the sacrum.
• The greater sciatic notch is below the auricular surface; the ischium has a body (posterior 2/5 of acetabulum) and ramus.
• The ischial tuberosity is the part you sit on; the pubis has a body (anterior 1/5 of acetabulum), superior and inferior rami.
• The obturator foramen is formed by the pubic and ischial rami.
• The femur's proximal end includes the head, neck, greater and lesser trochanters, and fovea capitus.

Pelvic Features and Articulations

• Hip joint: synovial, ball and socket, freely movable.
• Pubic symphysis: cartilaginous, symphysis, slightly movable.
• Sacroiliac (SI) joint: synovial, irregular gliding, slightly movable.
• Pelvic brim divides the greater (false) and lesser (true) pelvis.
• Superior (inlet) and inferior (outlet) apertures define pelvic boundaries.

Gender Differences in Pelvis

• Female pelvis: lighter, wider, oval inlet, wider outlet, >90° pubic arch.
• Male pelvis: heavier, narrower, round inlet, acute pubic arch <90°.

Radiographic Positioning and Procedures

• To position for hip imaging, locate the ASIS and the pubic symphysis.
• Internally rotate feet and lower limbs 15-20° for AP pelvis.
• CR for AP pelvis: on MSP, midway between ASIS and pubic symphysis (about 2" above pubic symphysis).
• Greater trochanters are shown in profile with correct AP positioning.
• Modified Cleaves (frog-leg): thighs abducted 45°, demonstrates femoral necks.
• Danelius-Miller: axiolateral view of the hip, limb rotated 15-20° unless contraindicated.
• Clements-Nakayama: modified axiolateral for trauma cases, CR angled 15° posterior.
• Judet views for acetabulum: internal (RPO) and external (LPO) obliques demonstrate specific columns/rims.
• Taylor method (outlet): CR 20-45° cephalic, 2" below pubic symphysis.
• Bridgeman method (inlet): CR 40° caudal at ASIS level.
• Suspended respiration for pelvic/hip imaging.

Key Terms & Definitions

• ASIS — Anterior Superior Iliac Spine, a palpable iliac landmark.
• Acetabulum — Socket formed by ilium, ischium, and pubis for femoral head.
• Obturator foramen — Large opening in hip bone formed by pubic and ischial rami.
• Ischial tuberosity — Part of ischium supporting body when sitting.
• Trochanter — Bony prominences (greater/lesser) at femur proximal end.
• Fovea capitus — Depression on femoral head for ligamentum capitis femoris.
• Pelvic brim — Oblique ridge dividing greater and lesser pelvis.
• Sacroiliac (SI) joint — Articulation between ilium and sacrum.
• Inlet/Outlet — Superior/inferior boundaries of pelvic cavity.
• Modified Cleaves — AP oblique hip projection, "frog-leg" position.
• Danelius-Miller — Axiolateral hip projection for trauma.

Action Items / Next Steps

• Review key pelvis and hip landmarks for identification on images.
• Practice radiographic positioning techniques and understand CR locations for all hip and pelvis projections.
• Memorize differences between male and female pelvis and composition of acetabulum.
• Complete any assigned readings or practice flashcards for further review.