Hilgenreiner and Perkins lines

Hilgenreiner line is a horizontal line through the upper margin of the radiolucent triradiate cartilage. Perkins line is a vertical line drawn from the most lateral ossified margin of the roof of the acetabulum and perpendicular to Hilgenreiner line. In the normal hip, the medial end of the ossified upper femoral metaphysis lies medial to Perkins line and inferior to Hilgenreiner line. In the subluxated hip, it lies lateral to Perkins line. In the dislocated hip, the medial end of the ossific metaphysis of the femoral neck lies lateral to Perkins line and superior to Hilgenreiner line.