OUTLINE

SUMMARY OF PROJECTIONS

ANATOMY

The pelvis serves as a base for the trunk and a girdle for the attachment of the lower limbs. The pelvis consists of four bones: two hip bones, the sacrum, and the coccyx. The pelvic girdle is composed of only the two hip bones.

Hip Bone

The hip bone is often referred to as the os coxae, and some textbooks continue to refer to it as the innominate bone. The most widely used term is hip bone.

The hip bone consists of the ilium, pubis, and ischium (Figs. 7-1 and 7-2). These three bones join together to form the acetabulum, the cup-shaped socket that receives the head of the femur. The ilium, pubis, and ischium are separated by cartilage in children but become fused into one bone in adults.

The hip bone is divided further into two distinct areas: the iliopubic column and the ilioischial column (see Fig. 7-2, C). These columns are used to identify fractures around the acetabulum.

Proximal Femur

The femur is the longest, strongest, and heaviest bone in the body. The proximal end of the femur consists of a head, a neck, and two large processes: the greater and lesser trochanters (Fig. 7-4). The smooth, rounded head is connected to the femoral body by a pyramid-shaped neck and is received into the acetabular cavity of the hip bone. A small depression at the center of the head, the fovea capitis, attaches to the ligamentum capitis femoris (Fig. 7-5; see Fig. 7-4). The neck is constricted near the head but expands to a broad base at the body of the bone. The neck projects medially, superiorly, and anteriorly from the body. The trochanters are situated at the junction of the body and the base of the neck. The greater trochanter is at the superolateral part of the femoral body, and the lesser trochanter is at the posteromedial part. The prominent ridge extending between the trochanters at the base of the neck on the posterior surface of the body is called the intertrochanteric crest. The less prominent ridge connecting the trochanters anteriorly is called the intertrochanteric line. The femoral neck and the intertrochanteric crest are two common sites of fractures in elderly adults. The superior portion of the greater trochanter projects above the neck and curves slightly posteriorly and medially.

The angulation of the neck of the femur varies considerably with age, sex, and stature. In the average adult, the neck projects anteriorly from the body at an angle of approximately 15 to 20 degrees and superiorly at an angle of approximately 120 to 130 degrees to the long axis of the femoral body (Fig. 7-6). The longitudinal plane of the femur is angled about 10 degrees from vertical. In children, the latter angle is wider—that is, the neck is more vertical in position. In wide pelves, the angle is narrower, placing the neck in a more horizontal position.

Articulations of the Pelvis

Table 7-1 and Fig. 7-7 provide a summary of the three joints of the pelvis and upper femora. The articulation between the acetabulum and the head of the femur (the hip joint) is a synovial ball-and-socket joint that permits free movement in all directions. The knee and ankle joints are hinge joints; the wide range of motion of the lower limb depends on the ball-and-socket joint of the hip. Because the knee and ankle joints are hinge joints, medial and lateral rotations of the foot cause rotation of the entire limb, which is centered at the hip joint.

The pubes of the hip bones articulate with each other at the anterior midline of the body, forming a joint called the pubic symphysis. The pubic symphysis is a cartilaginous symphysis joint.

The right and left ilia articulate with the sacrum posteriorly at the sacroiliac (SI) joints. These two joints angle 25 to 30 degrees relative to the midsagittal plane (see Fig. 7-7, B). The SI articulations are synovial irregular gliding joints. Because the bones of the SI joints interlock, movement is limited or nonexistent.

Pelvis

The female pelvis (Fig. 7-8) is lighter in structure than the male pelvis (Fig. 7-9). It is wider and shallower, and the inlet is larger and more oval-shaped. The sacrum is wider, it curves more sharply posteriorly, and the sacral promontory is flatter. The width and depth of the pelvis vary with stature and gender (Table 7-2). The female pelvis is shaped for childbearing and delivery.

The pelvis is divided into two portions by an oblique plane that extends from the upper anterior margin of the sacrum to the upper margin of the pubic symphysis. The boundary line of this plane is called the brim of the pelvis (see Figs. 7-8 and 7-9). The region above the brim is called the false or greater pelvis, and the region below the brim is called the true or lesser pelvis.

The brim forms the superior aperture, or inlet, of the true pelvis. The inferior aperture, or outlet, of the true pelvis is measured from the tip of the coccyx to the inferior margin of the pubic symphysis in the anteroposterior direction and between the ischial tuberosities in the horizontal direction. The region between the inlet and the outlet is called the pelvic cavity (Fig. 7-10).

When the body is in the upright or seated position, the brim of the pelvis forms an angle of approximately 60 degrees to the horizontal plane. This angle varies with other body positions; the degree and direction of the variation depend on the lumbar and sacral curves.

Localizing Anatomic Structures

The bony landmarks used in radiography of the pelvis and hips are as follows:

Most of these points are easily palpable, even in hypersthenic patients (Fig. 7-11). Because of the heavy muscles immediately above the iliac crest, care must be exercised in locating this structure to avoid centering errors. Having the patient inhale deeply is advisable; while the muscles are relaxed during expiration, the radiographer should palpate for the highest point of the iliac crest.

The highest point of the greater trochanter, which can be palpated immediately below the depression in the soft tissues of the lateral surface of the hip, is in the same horizontal plane as the midpoint of the hip joint and the coccyx. The most prominent point of the greater trochanter is in the same horizontal plane as the pubic symphysis (see Fig. 7-11).

The greater trochanter is most prominent laterally and more easily palpated when the lower leg is medially rotated. When properly used, medial rotation assists in localization of hip and pelvis centering points and avoids distortion of the proximal end of the femur during radiography. Improper rotation of the lower leg can rotate the pelvis. Consequently, positioning of the lower leg is important in radiographing the hip and pelvis; the feet must be immobilized in the correct position to avoid distortion of the image. Traumatic injuries or pathologic conditions of the pelvis or lower limb may rule out the possibility of medial rotation.

The pubic symphysis can be palpated on the midsagittal plane and on the same horizontal plane as the greater trochanters. By placing the fingertips at this location and performing a brief downward palpation with the hand flat, palm down, and fingers together, the radiographer can locate the superior margin of the pubic symphysis. To avoid possible embarrassment or misunderstanding, the radiographer should advise the patient in advance that this and other palpations of pelvic landmarks are part of normal procedure and necessary for an accurate examination. When performed in an efficient and professional manner with respect for the patient’s condition, such palpations are generally well tolerated.

The hip joint can be located by palpating the ASIS and the superior margin of the pubic symphysis (Fig. 7-12). The midpoint of a line drawn between these two points is directly above the center of the dome of the acetabular cavity. A line drawn at right angles to the midpoint of the first line lies parallel to the long axis of the femoral neck of an average adult in the anatomic position. The femoral head lies 1½ inches (3.8 cm) distal, and the femoral neck is 2½ (6.4 cm) distal to this point.

For accurate localization of the femoral neck in atypical patients or in patients in whom the limb is not in the anatomic position, a line is drawn between the ASIS and the superior margin of the pubic symphysis, and a second line is drawn from a point 1 inch (2.5 cm) inferior to the greater trochanter to the midpoint of the previously marked line. The femoral head and neck lies along this line (see Fig. 7-12).

SUMMARY OF PATHOLOGY

EXPOSURE TECHNIQUE CHART ESSENTIAL PROJECTIONS

RADIOGRAPHY

Pelvis and Upper Femora

AP PROJECTION

Image receptor: 14 × 17 inch (35 × 43 cm) crosswise

Position of patient:

• Place the patient on the table in the supine position.

Position of part:

• Center the midsagittal plane of the body to the midline of the grid, and adjust it in a true supine position.

• Unless contraindicated because of trauma or pathologic factors, medially rotate the feet and lower limbs about 15 to 20 degrees to place the femoral necks parallel with the plane of the image receptor (IR) (Figs. 7-15 and 7-16). Medial rotation is easier for the patient to maintain if the knees are supported. The heels should be placed about 8 to 10 inches (20 to 24 cm) apart.

Fig. 7-15 A, AP pelvis with femoral necks and trochanters poorly positioned because of lateral rotation of limbs. B, Feet and lower limbs in natural, laterally rotated tabletop position, causing poor profile of proximal femora in A.

Fig. 7-16 A, AP pelvis with femoral necks and trochanters in correct position. B, Feet and lower limbs medially rotated 15 to 20 degrees, correctly placed with upper femora in correct profile in A.

• Immobilize the legs with a sandbag across the ankles, if necessary.

• Check the distance from ASIS to the tabletop on each side to be sure that the pelvis is not rotated.

• Center the IR midway between ASIS and pubic symphysis. In average-sized patients, the center of the IR is about 2 inches (5 cm) inferior to ASIS and 2 inches (5 cm) superior to pubic symphysis (Fig. 7-17).

Fig. 7-17 AP pelvis.

• If the pelvis is deep, palpate for the iliac crest and adjust the position of the IR so that its upper border projects 1 to 1½ inches (2.5 to 3.8 cm) above the crest.

• Shield gonads.

• Respiration: Suspend.

Central ray:

• Perpendicular to the midpoint of the IR

Collimation:

• Adjust to 14 × 17 inches (35 × 43 cm) on the collimator.

Structures shown: The image shows an AP projection of the pelvis and of the head, neck, trochanters, and proximal one third or one fourth of the shaft of the femora (Fig. 7-18).

Fig. 7-18 A, Male AP pelvis. B, Female AP pelvis.

EVALUATION CRITERIA

The following should be clearly shown:

 Evidence of proper collimation

 Entire pelvis along with the proximal femora

 Lesser trochanters, if seen, shown on the medial border of the femora

 Femoral necks in their full extent without superimposition

 Greater trochanters in profile

 Both ilia equidistant to the edge of the radiograph

 Both greater trochanters equidistant to the edge of the radiograph

Only gold members can continue reading. Log In or Register to continue

Share this:

• Click to share on Twitter (Opens in new window)
• Click to share on Facebook (Opens in new window)

Related posts:

COMPENSATING FILTERS BONY THORAX THORACIC VISCERA VERTEBRAL COLUMN SHOULDER GIRDLE UPPER LIMB

Stay updated, free articles. Join our Telegram channel

Join