Schematic illustration of the lines used to measure the width of the pelvis and greater trochanters, and the acetabular index. The midline was defined as the line perpendicular and bisecting the line that joined to two tear drops. (A) The width from the midline to the anterior inferior iliac spine – the reference width. (B) The width from the midline to the most lateral aspect of the acetabulum. (C) The width from the midline to the most superior point of the greater trochanter. (D) The width from the midline to the most lateral aspect of the greater trochanter.