Technical factors and patient positioning are the same as for an AP pelvis (bilateral hips) exam. No motion is evidenced by sharp orbicular markings of the proximal femora and the pelvic structures.Īn AP unilateral hip study is usually a postoperative or a follow-up exam to demonstrate the acetabulum, femoral head and neck, and the greater trichinae, as well as the condition and placement of any existing orthopedic appliance.Optimal exposure should clearly demonstrate L5, sacral area, and margins of the femoral heads and acetabula without overexposing the ischium and the pubic bones.Correct collimation and centering is evidenced by demonstration of both ilia equidistant to the edge of the radiograph, both greater trochanters equidistant to the edge of the radiograph, and the lower vertebral column centered to the middle of the radiograph.A closed or narrowed obturator foramen indicates rotation in that direction. No rotation is evidenced by symmetric appearance of the two obturator foramina, as well as a symmetric iliac alae and ischial spines.The greater trichinae should be visible in profile. The lesser trochanters usually are not visible at all, or if they are, should appear equal in size and shape on the medial border of the femora.The entire pelvis along with proximal femoral neck including pelvic girdle, L5, sacrum, and coccyx should be seen.Ask the patient to suspend their breathing on expiration.Įvaluation criteria for AP pelvis (bilateral hips).Ovarian shielding on females, however, is generally not possible without obscuring essential pelvic anatomy (unless interest is in area of hips only). For a pelvis with bilateral hips projection, carefully palpate the superior portion of the iliac crest and direct the central ray (CR) midway between the level of the ASIS and the symphysis pubis.The center of the cassette should be midway between the ASIS and the pubic symphysis. For correct centering of the pelvis (bilateral hips), palpate for the iliac crest and adjust the position of the cassette so that the upper border of the cassette is 1-1 ½ inches (2.5-3.8 cm) above the iliac crest.The heels should be 8-10 inches (20-24 cm) apart. This is done to overcome the normal anteversion of the femoral necks and to place their longitudinal axes parallel to the film. The feet are placed in approximately 15°-20° of internal (medial) rotation.The distance from tabletop to each anterior superior iliac spine (ASIS) should be equal. There should be no rotation of the pelvis. The midsagittal plane of the body should be centered to the midline of the grid device.Placing a support under the head and knee helps to relieve the strain on the patient while in the supine position. The patient is positioned supine on the radiographic table, with arms placed at the side or across the upper chest.Positioning for the AP pelvis (bilateral hips) projection Surface-to-image distance (SID) of 40 inches (100 cm).Image receptor (IR): 14 x 17 inch (35 x 43 cm) crosswise.Varus and valgus configuration of a femoral neck fracture is said to occur if there is decrease or increase, respectively, in this angle. Normally, the angle formed by these axes ranges from 125°-135°. This view also demonstrates an important anatomical relationship in the longitudinal axes of the femoral neck and shaft. Most traumatic conditions involving the sacral wings, the iliac bones, ischium, the pubis, and the femoral head and neck can sufficiently be evaluated on the AP projection of the pelvis and hip. The standard radiographic view for the pelvis is obtained in an AP position with the patient supine. Special radiographic projections are performed to evaluate the SI joints, sacral bones, and acetabulum. The AP view is frequently not sufficient to provide adequate evaluation of the entire sacral bone, the sacroiliac (SI) joints, and the acetabulum. AP oblique pelvis (the “frog leg”) projections are commonly performed on non-trauma patients to evaluate congenital hip dislocation. If you'd like to comment on or contribute to this series, please e-mail standard radiographic projections used to evaluate injury to the pelvic girdle and proximal femur include the anteroposterior (AP) pelvis (bilateral hips) and AP unilateral hip. This article is the 16th in our series of white papers on radiologic patient positioning techniques for x-ray examinations.
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