Figure 8

Schematic illustrations of the modified group. The 48 mm deep enlarged screw tract was formed by a 5.5 mm twist metric drill bit (A), and 0.8 ml PMMA was retrograde injected into the enlarged screw hole (B). A tapping screw was inserted into the PMMA- filled hole (C). After setting for 7 min, the screw was carefully removed, leaving a stiff threaded PMMA hole (D). A cylindrical or conical repair screw, sized according to that used in the traditional technique, was implanted (D, E). Vertebra with complete insertion of the repair screw (F).