Fig. 2
From: Computer simulation of optimal lipped polyethylene liner orientation against prosthetic impingement
a The coordinate system determined by the International Society of Biomechanics. b The view of the acetabular opening plane to show the orientation of the elevated rim. One line connected the center of the acetabular circle and the midpoint of the elevated rim. The other line was intersected by the acetabular opening plane and the y–z axial plane. The angle ω formed by these two lines was the orientation of the elevated rim