Comparison of pullout strength of small-diameter cannulated and solid-core screws.

The purpose of this study was to determine the difference in pullout strength between cannulated and solid-core small-diameter bone screws. Cannulated screws from different manufacturers were compared against solid-core screws with 2.0-mm, 2.4-/2.5-mm, and 3.0-mm diameters. A synthetic material made to simulate bicortical bone was used as the test medium. The screws were extracted under servohydraulic control. There was no statistically significant difference between any of the cannulated and solid-core 2.0-mm screws used in this study (P <.05). In the 2.4-/2.5-mm screw tests, both of the cannulated screw designs had a significantly higher pullout strength when compared with the solid-core screw (P <.05). In the testing of 3.0-mm screw test, 1 of the cannulated screw designs showed a significantly higher pullout strength than the other cannulated and solid-core screws that were tested (P <.05). The results of this study suggest that small-diameter cannulated bone screws are similar in mechanical pullout strength to solid-core screws.