The pelvis is made up of 3 bones, the ilium, ischium, and pubis. The Ilium articulates with the sacrum to for the sacroiliac joints (SI), and all the bones articulate together to form the acetabulum joint socket. There are 3 anatomic landmarks on the pelvis, the iliac crest, ASIS and pubic symphysis.
There are also differences between the male and female pelvis, which is a factor that must be taken into consideration when imaging the pelvis. The female pelvis is wider, with the ilia more flared and shallower from front to back with a pubic angle of greater than 90 degrees. The male pelvis is narrower, deeper, or less flared with a heart-shaped pelvis inlet with a pubic angle of less than 90 degrees.
The area superior to the oblique plane of the pelvic brim is termed the greater or false pelvis. The area inferior to the oblique plane is termed the lesser or true pelvis, which forms the birth canal.
Pelvis
Imaging / Pathologies
The routine for a pelvis radiograph is a 1 view AP pelvis. Most facility protocols include a pelvis when imaging the hip. This view can be performed erect if fracture or dislocation is not suspected. The patients’ feet must be internally rotated 15-20 degrees to place femoral necks parallel to the IR, again only if fracture or dislocation is not suspected. This can visualize pathologies like a hip fracture, and ankylosing spondylitis which affects the SI joints
Special views for the pelvis
AP modified cleaves – Bilateral frog leg
Demonstration of nontraumatic hip conditions, developmental hip dysplasia. Abduct both femora 40-45 degrees vertical with plantar surfaces of the feet together and direct the CR 3in distal to the ASIS.
AP axial inlet pelvis
Assessment of pelvis trauma for posterior displacement or inward/outward rotation of the anterior pelvis. A 40-degree caudal angle is applied and directed at the level of the ASIS.
Judet method
Demonstrates acetabular fractures, and pelvic ring fractures. 45-degree R and L obliques are obtained.
Affected side down has a perpendicular CR that is centered 2 inches distal and medial to the downside ASIS, this demonstrates the anterior rim of the acetabulum and the posterior ischial column as well as the iliac wing.
Affected side up also has a perpendicular CR but it is directed 2 inches directly distal to the upside ASIS. This visualizes the posterior rim of the acetabulum and anterior ischial column as well as the obturator foramen.
If a pelvic ring fracture is suspected due to a contrecoup injury, the entire pelvis should be included on the radiograph. Centering should be adjusted to include both hips.
AP axial outlet projection
Demonstrates bilateral views of pubis and ischium to allow assessment of pelvic traumatic fracturs or displacements. A cephalic angle is applied to the CR – 2035 degrees for males, 30-45 degrees for females – directed 1 to 2 inches distal to the superior border of symphysis pubis.
Pelvis
3.
1. vertebral body of L5
2. left acetabular roof
left anterior acetabular wall
4. left ischial tuberosity
5. right ilium
Pelvis
PA axial acetabulum “Teufel method”
Visualizes acetabular fractures, especially the superioposterior wall. The patient is in a 35–40-degree anterior oblique with the affected side down. The CR is angled 12 degrees cephalic and is directed 1 inch superior to the greater trochanter, 2 in lateral to MSP.
HIP
The hip is made up of the proximal femur and the acetabulum of the pelvis. The femur, which is a long bone, articulates with the acetabulum as a diarthrodial ball-and-socket joint. The head of the femur fits into the acetabulum. Other anatomy relative to the hip is the femoral neck, which is used for several imaging projections, the greater and lesser trochanters, and proximal body of the femur. The anatomic landmark on the hip is the greater trochanter, which corresponds to the level of the symphysis pubis.
The hip localization method can be utilized to find both the head and the neck of the femur. An imaginary line is drawn from the ASIS to the symphysis pubis, and from the midpoint of that line you can go 1 ½ inches perpendicular to find the head, 2 ½ inches to find the neck. This method comes into play when positioning for several of the unilateral hip studies.
Imaging / Pathologies
Routine Hip
Unilateral AP Hip
Post-op or follow-up examination to demonstrate acetabulum, femoral head, neck, and greater trochanter. Demonstrates degenerative joint disease or, osteoarthritis. The CR is perpendicular to the femoral neck, which can be located with the hip localization method, or is 1-2 inches medial, 3-4 inches distal to the ASIS. The affected leg is internally rotated 15-20 degrees if patient conditions allow.
Modified Cleaves Unilateral Frog Leg
Lateral view for nontraumatic injuries. Abduct femur 45 degrees from vertical and the CR is perpendicular to the IR and directed to the femoral neck.
For all hip projections, if there is any ortho devices, they must be included on the radiograph in their entirety.
HIP
Special Views Hip
Clements-Nakayama method
Should be performed for a lateral fracture assessment when the pt has limited movement in both lower limbs and Danelius-miller method cannot be obtained. Keep the legs in a neutral position and rest the IR on an extended bucky tray. Tilt IR 15 degrees from vertical and angle the CR mediolaterally as needed so that is perpendicular and centered to the femoral neck. Apply a 15-20 degree posterior angle to match the IR.
Danelius-Miller Method (cross table hip)
Lateral view for fractures / dislocations in trauma hip situations when affected leg cannot be abducted. The IR is placed parallel to femoral neck and perpendicular to the CR in the crease above the iliac crest. Internally rotate the affected leg 15-20 degrees unless contraindicated. Raise the unaffected leg to move it out of the field of view.
Other Pathologies
Foreign bodies (butt stuff)
Chondrosarcoma
Open book fracture
Modalities
Xray is the primary modality for trauma fractures and initial views of the hip and pelvis.
CT can be used to visualize fractures in greater detail and is often used for surgical planning. It can be used to visualize soft tissue and blood vessel damage in the pelvic area.
MR can be utilized for soft tissue injuries aswell.
Ultrasound is the first option for developmental hip dysplasia due to diagnosis’ occur in young children since it utilizes no ionizing radiation.
REFERENCES
Lampignano, J. P., & Kendrick, L. E. (2021). Bontrager’s textbook of radiographic positioning and related anatomy (10th ed.). Elsevier.
