The coccyx and symphysis pubis are in a straight line and are positioned in the middle line of the image both sides of the iliac wings and obturator foramina are symmetric, while the distance between the superior border of the pubic symphysis and the tip of the coccyx is between 1 and 3 cm. Lastly, accurate preoperative templating may not be achieved and measurement errors could be resulted when performing studies dealing with radiographic assessments 1). For instance, they may make it difficult to diagnose a valgus-impacted fracture of the femoral neck and lead to a misdiagnosis of an osteophyte as a stress fracture. These errors may negatively affect fracture diagnosis. As mentioned above, the most common error in taking an anteroposterior hip radiograph is that the hip is externally rotated while the image is being taken in this case, the greater trochanter overlaps with the femoral head and the posterior head-neck junction is projected to the superior to the anterior head-neck junction, thereby distorting the image. The likelihood of inappropriate correction of femoral anteversion was reported to be lower if the thickness of the lesser trochanter is less than 5 mm 3). In addition, the greater and lesser trochanters should be clearly distinguishable, while the greater trochanter may not significantly overlap with the femoral neck the calcar femoris needs to be clearly visible and there should be very little elliptical overlap between the anterior and posterior margins of the head-neck junction. In a standard anteroposterior hip radiograph, the coccyx and symphysis pubis should be in a straight line and positioned in the middle line of the image, both sides of the iliac wings and obturator foramina should be symmetric, while the distance between the superior border of the pubic symphysis and the tip of the coccyx should be between 1 and 3 cm 2) ( Fig. In particular, the tilt and rotation of the pelvis should be known precisely during evaluation of an anteroposterior hip radiograph. In order to evaluate an image, it is critical to confirm that it was properly taken and the patient was in an appropriate position. Lastly, the false-profile view of the hip is obtained with the pelvis rotated 65° relative to the bucky wall stand, with the foot on the affected side parallel to the radiographic cassette ( Fig. In the cross-table lateral view, a lower extremity is internally rotated by 15°-20° in a supine position and then the hip and knee joints on the other side are flexed to prevent interference in radiographic projection a cassette is positioned on the side of the hip at the right angle relative to the incidence angle, thereby projecting toward the groin region at 35°-45° of incidence parallel to the longitudinal axis of the femur ( Fig. In the Löwenstein view, patient is turned onto the affected hip at least 45° with the hip flexion angle of 90° and internal rotation angle of 45° in a supine position and then images of each side are taken vertically from the groin region ( Fig. In the frog-leg lateral view, both sides are shown on one image and the knee joint is flexed 30°-40° in a supine position, while the hip is externally rotated by 45° so that the image is taken toward the middle of the line connecting the upper symphysis pubis and the anterior-superior iliac spine ( Fig. There are multiple imaging techniques for lateral hip radiography, including the frog-leg lateral view, Löwenstein view, and cross-table lateral view. In a supine position, the image is taken toward the middle of the line connecting the upper part of the symphysis pubis and anterior-superior iliac spine (ASIS) either both patellae should be facing forward or lower extremities should be internally rotated by 15°-20° to accommodate femoral anteversion in anteroposterior hip radiographs. Positioning for an anteroposterior hip radiograph. In such cases, accurate anteroposterior images may not be achievable, and the patient should be removed from the table and then both legs should be positioned perpendicularly in a flexion position for radiography. Flexion contracture may increase or decrease image magnification. Thus, either both patellae should be facing forward or lower extremities should be internally rotated by 15°-20° to accommodate femoral anteversion in anteroposterior hip radiographs ( Fig. If anteroposterior hip radiographs are taken in a supine position, one of the most common mistakes is image distortion as the hip is externally rotated 1). An anteroposterior hip radiograph includes images of both sides of the hip on the same film and projects towards the middle of the line connecting the upper symphysis pubis and anterior-superior iliac spine the distance between the X-ray tube and the film should be 1.2 m. In plain radiography (X-ray), anteroposterior and lateral hip radiographs are usually taken.
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