Pelvic Anatomy and Radiographs

Overview

This lecture reviews the anatomy of the pelvis, focusing on identifying key bony landmarks, muscle attachments, and ligaments observed in pelvic radiographs and 3D models.

Pelvic Bones and Landmarks

• The pelvis comprises two pelvic bones fused at the pubic symphysis and separated posteriorly by the sacrum.
• Each pelvic bone develops from three segments: ilium (iliac crest), ischium (posterior), and pubis (anterior).
• All three bones fuse to form the acetabulum, the socket for the femoral head, forming the hip joint.
• The sacrum articulates superiorly with L5 and inferiorly with the coccyx; features include sacral promontory, sacral foramina, and sacral ala.
• Key iliac landmarks: iliac crest, anterior/posterior superior iliac spine, and anterior/posterior inferior iliac spine.
• The ischium contains the ischial tuberosity and ischial spine; the pubis forms the superior and inferior pubic rami.

Radiograph Anatomy and Pelvic Lines

• Radiographs show the greater and lesser trochanters (femur), femoral neck, and the acetabulum's anterior and posterior rims.
• Pelvic stability is visualized by the iliopectineal (pelvic ring) and ilioischial lines; smoothness indicates no fracture.
• Shenton's line runs from the medial femur to the inferior border of the superior pubic ramus.
• Disruption of these lines suggests possible fractures and warrants further evaluation.

Muscles and Attachments

• Iliopsoas (psoas + iliacus) originates from the lumbar spine/iliac wing to the lesser trochanter.
• Sartorius attaches to the anterior superior iliac spine; rectus femoris to the anterior inferior iliac spine.
• Gluteus minimus/medius, piriformis, obturator internus/externus, and quadratus femoris attach to or near the greater trochanter.
• Adductors (pectineus, adductor longus/brevis, gracilis) originate near the pubic rami and pectineal line.

Pelvic Ligaments and Stability

• Ileolumbar ligaments connect lumbar vertebrae to the ilium for upper pelvic stability.
• Sacroiliac ligaments (anterior/posterior) stabilize the SI joints.
• Hip joint stabilized by iliofemoral, pubofemoral, and ischiofemoral ligaments, which prevent anterior dislocation.
• Inguinal ligament runs from anterior superior iliac spine to pubic tubercle, forming the floor of the inguinal canal.
• Sacrospinous and sacrotuberous ligaments create greater and lesser sciatic foramina.

Key Terms & Definitions

• Acetabulum — hip socket formed by fusion of ilium, ischium, and pubis.
• Iliopsoas — muscle formed from psoas major and iliacus, inserting on the lesser trochanter.
• Pelvic ring — bony ring formed by the pelvis, prone to multiple fractures.
• Shenton's line — radiographic line indicating femoral and pelvic alignment.
• Sacral promontory — the prominent upper part of the sacrum.

Action Items / Next Steps

• Review labeled diagrams of the pelvis to reinforce bony landmarks.
• Practice identifying pelvic lines and signs of fracture on sample radiographs.
• Learn key muscle and ligament attachments for potential exam questions.