On an anteroposterior (AP) pelvis radiograph, the feet need to be rotated to what degree to place the femoral necks parallel to the image receptor?

To achieve proper alignment of the femoral necks parallel to the image receptor in an anteroposterior (AP) pelvis radiograph, a medial rotation of approximately 15-20 degrees is typically required. This rotation is essential due to the anatomical positioning of the femoral necks, which are angled in relation to the pelvis.

When the feet are rotated within this range, it helps to correctly position the femoral necks, ensuring that they are included effectively within the radiographic image and avoiding any foreshortening. Proper rotation is crucial for accurate visualization of the hip joint and surrounding structures, aiding in diagnosis and assessment.

Other options suggest either insufficient or excessive rotation. A smaller rotation, such as 5-10 degrees, may not adequately position the femoral necks, while excessive rotation at 25-30 degrees could lead to misalignment and an unnatural representation of the anatomy. A lateral rotation of 45 degrees is inappropriate as it moves the feet in the opposite direction needed to align the femoral necks accurately. Thus, the required medial rotation of 15-20 degrees is the optimal choice for achieving the necessary positioning on the radiograph.