The Role of Pedicle Screw Surface on Insertion Torque and Pullout Strength.

 Compare by mechanical tests the pullout resistance and the insertion torque of rough and smooth pedicle screws.  Pedicle screws with rough surface and smooth surface, with diameters of 4.8; 5.5 and 6.5 mm, were inserted in polyurethane blocks with density of 10 PCF (0.16 g/cm3). Insertion torque and pullout strength were assessed.  The pullout strength of the rough surface and smooth surface screws did not differ, except in the group of 4.8 mm diameter screws. In this group, the rough surface screws showed greater resistance to pullout.  Pedicle screws with a rough surface did not show increased pullout resistance in the acute phase of their insertion in polyurethane blocks compared to smooth surface screws. The rough surface screws had a higher insertion torque than the smooth surface screws, depending on the diameter of the screw and the preparation of the pilot hole.