Volume 49 No 1  Cover Story

Consecutive schematic illustrations of the modified transpedicular screw augmentation procedure and operation findings. First low : The vacant pedicle hole after removal of the loose pedicle screw (left). The PMMA insertion process. When the PMMA’s viscosity became like toothpaste, we filled the dead space with about 1 cc of PMMA (center). The inserted PMMA hardens with the small pilot screw inserted (right). Second low : The inner thread created by the small screw is presented after the small pilot screw was removed (left). Intra-operative photograph shows the inner thread (white arrow) after removing the small pilot screw (right). Third low : The cracks (red arrows), caused by inserting the thicker permanent screw, gives the screw greater holding power (anchor bolt effect) (left). Illustrations of axial and coronal section after thicker permanent screw insertion. We suppose the thicker permanent screw has greater expansile forces (red arrows) and holding powers (blue arrows) throughout its whole surface (center and right).