Fig. 5

The offset of the X-ray beam measured on an AP radiograph of both hips. The X-ray beam focused on the pubic symphysis. In this figure, the X-ray beam offset angle in the ilioischial line can be calculated by a trigonometric function, using the distance from the center of the pelvis to the ilioischial line and the distance from the X-ray source to the film. With this method, an X-ray beam offset angle of approximately 4° is located around the ilioischial line