Screw to fix reinforcement rod along spinal column; has U-shaped recess for reinforcement rod with saw-tooth thread having surfaces at negative angle to secure fixing screw

摘要

The screw (1) has a threaded shaft for insertion in a vertebra and a head (3) with a U-shaped recess (4) for a reinforcement rod and an inner thread (8) at the legs (6,7) of the U, to secure the rod with a fixing screw. The inner thread is asymmetrically formed as a saw-tooth thread, with each surface that contacts the fixing screw having a negative angle.