[Revision of Pelvic Rotation Angle and One Idea for Improving Reproducibility of Hip Joint Radiographic Images (False...

Radiographic images of the hip joint can include a false profile view when the foot of the affected side is positioned parallel to the detector plane and the pelvic rotation angle is 65°. However, to the best of our knowledge, pelvic rotation angle has yet to be adequately investigated. The present study aimed to improve radiographic imaging reproducibility by testing pelvic rotation angles using the pubic symphysis and greater trochanter as a guide. The pubic bone angles were 50°-60° independent of gender or age in approximately 70% of 210 hip joints examined by computed tomography. When the line connecting the centers of the femoral neck and the pubic symphysis was based on a detector plane during hip joint magnetic resonance imaging of 12 healthy volunteers, pubic bone angles were approximately 65° and 62° when rotated outwards at 20° and 30°, respectively. Based on the detector plane, the difference between the angle at the intersection of the line connecting the femoral neck center and the pubic symphysis center and the angle at the intersection of the line connecting the pubic symphysis superior margin and the greater trochanter was <4° at external rotation angles of 10°, 20°, and 30°. The foot of the affected side corresponding to the detector plane in front of the body at approximately 65° and the second metatarsal at a pelvic rotation angle when collimated was rotated 25° outwards. Radiation is incident on the pubic symphysis and the greater trochanter can be used as an ejection point.