The mean ultimate pullout strengths of various types of expansive screws.The vertical lines represent the standard deviations. Horizontal lines above the bars indicate groups that were not significantly different from each other.

<p>Regardless of the screw design (screws with 4 or 6 slits and EELs of 16 or 22 mm, or a solid screw), screws with cement augmentation demonstrated significantly higher pullout strengths than did pedicle screws without cement augmentation (p < 0.001).