Pelvis and Upper Femora Study Notes

Chapter 7: Pelvis and Upper Femora

Lesson 1: Anatomy and Procedures of the Pelvis and Upper Femora

1. Anatomy Review

• The pelvis consists of four bones:

  • Right and left innominate, or hip, bones

  • Sacrum

  • Coccyx

• Functions:

  • Serves as the base for the trunk

  • Acts as a girdle for lower limb attachment

2. Pelvic Girdle

• Definition: Composed only of the two hip bones, also known as:

  • Os coxae

  • Innominate

• Each hip bone has three parts:

  • Ilium

  • Ischium

  • Pubis

• The three bones come together to form the acetabulum, the cup-shaped socket that articulates with the head of the femur.

3. Ilium

• Structure: Consists of a body and a broad, curved portion called the ala

• Function: The body forms the superior two-fifths of the acetabulum.

• **Prominent Processes:

  1. Anterior superior iliac spine (ASIS)

  2. Anterior inferior iliac spine

  3. Posterior superior iliac spine

  4. Posterior inferior iliac spine**

• The superior margin is referred to as the iliac crest.

• The posterior, inferior part ends in the greater sciatic notch.

4. Ischium

• Composition: Consists of:

  • Body

  • Ischial ramus

• Function: The body forms the posterior two-fifths of the acetabulum, and the ischial ramus joins with the inferior ramus of the pubis.

• Features:

  • Ischial tuberosity: The expanded portion on which the trunk rests when seated.

  • Ischial spine: Located on the upper, posterior part of the body.

  • Lesser sciatic notch: An indentation just below the ischial spine.

5. Pubis

• Composition: Consists of:

  • Body

  • Superior ramus

  • Inferior ramus

• Function: The body forms about one-fifth of the anterior acetabulum.

• Obturator foramen: Formed by the junction of the ischial ramus and pubis inferior ramus.

6. Ilium and Ischium (Detailed Anatomy)

• Iliac fossa

• Hip Bone Components:

  • Iliac crest

  • Ilium

  • Auricular surface

  • Anterior superior iliac spine

  • Anterior inferior iliac spine

  • Body (of ilium)

  • Acetabulum

  • Body (of pubis)

  • Ischium

  • Ala

  • Obturator foramen

  • Arcuate line

  • Ischial ramus

  • Posterior superior iliac spine

  • Posterior inferior iliac spine

  • Spine of Ischium

  • Superior ramus

  • Pubis

  • Inferior ramus

  • Ischial ramus

7. Joints of the Pelvis

• Sacroiliac (SI) Joints:

  • Articulation between the right and left ilia and the sacrum.

  • Type: Irregular, gliding.

• Hip Joints:

  • Articulation of the head of the femurs with the acetabula.

  • Type: Synovial, ball-and-socket.

• Pubic Symphysis:

  • Junction of the right and left pubic bones in the midline.

  • Type: Cartilaginous, slightly moveable joint.

8. Gender Differences in Pelvic Anatomy

• Males:

  • Heavier, narrower, deeper.

  • Angle at pubic symphysis is acute.

• Females:

  • Wider, shallower, lighter.

  • Angle at symphysis is obtuse.

9. Localizing Anatomy

• Important bony landmarks include:

  • Iliac crest

  • ASIS

  • Pubic symphysis

  • Greater trochanter

  • Ischial tuberosity

  • Tip of coccyx

• Localization insights:

  • The highest point of the greater trochanter lies in the same horizontal plane as the midpoint of the hip joint and coccyx.

  • Most prominent point of the greater trochanter is in the same horizontal plane as the pubic symphysis.

10. Hip Joint Localization Techniques

• Palpation Technique:

  • Palpate ASIS and the superior margin of the pubic symphysis.

  • Draw a line connecting the two, with the midpoint directly above the acetabular cavity center dome.

  • Draw a line at a right angle to the midpoint of the above line, which parallels the femoral neck.

• Measurements:

  • Femoral head = 1.5 inches (3.8 cm) distal.

  • Femoral neck = 2.5 inches (6.4 cm) distal.

11. General Procedural Guidelines

Patient Preparation

• Artifact Removal:

  • Remove undergarments (especially elastic materials a source of artifact).

  • Remove clothing and provide a gown (if necessary).

General Patient Position

• Ambulatory Patients:

  • Position: Supine on x-ray table.

• Nonambulatory Patients:

  • Use proper transfer techniques to table or grid IR if transfer is not possible.

IR Size and SID

• Consult textbooks for guidelines on grid IR size.

• Standardized SID:

  • When not specified, Merrill’s Atlas recommends a SID of 48 inches (122 cm).

ID Markers

• Include right or left side markers on images and any other required ID markers in the blocker or elsewhere on the final image.

Radiation Protection Techniques

• Recommended shielding:

  • Shield male patients according to guidelines.

  • Shielding for females may obscure anatomy.

• General radiation protection measures include:

  • Close collimation.

  • Use optimum technique factors.

12. Patient Instructions

• Explain positions and breathing instructions to the patient.

• Inform that respirations should be suspended during exposure.

13. Radiographic Procedures

Essential Projections: Pelvis and Upper Femora, Femoral Necks, Hip, and Acetabulum

• AP Pelvis and Upper Femora: Patient position is supine.

• Part Positioning: Ensure the MSP of the body is centered to midline and that ASIS to table distance is equal on both sides. Medially rotate feet and lower limbs 15 to 20 degrees to place femoral necks parallel with IR but do not rotate if trauma is suspected.

• Upper border of IR should be 1 to 1.5 inches (2.5 to 3.8 cm) above the crests.

• CR: Perpendicular to IR and collated field based on IR size.

14. AP Oblique (Modified Cleaves) for Femoral Necks

• Note: This method is contraindicated if fracture or pathology is suspected.

• Patient position: Supine; no rotation of pelvis; ASIS should be equidistant from table top.

• Part Position for Bilateral: Flex hips and knees, abduct thighs, and place soles of the feet together for support.

• CR: Perpendicular to MSP at 1 inch (2.5 cm) above the pubic symphysis.