Figure 7.

The three patterns of the screw insertion region. Left: The anterior and posterior boundaries show a blunt V-shape. An increase in the outward inclination of the screw at the line tangential to the obturator may result in obturator penetration. Middle: The anterior and posterior boundaries do not intersect. An increase in the outward inclination of the screw at the line tangential to the obturator may result in pelvis penetration. Right: The anterior and posterior boundaries show a sharp V-shape. The screw at the line tangential to the obturator is tangential to the anterior and posterior boundaries. Penetration of the anterior and posterior cortices may occur when the outward inclination of the screw is tangential to the obturator. Note: The red dot in the figure is a simulated axis view of the 3.5-mm screw.