The present invention relates to one kind to be used for guide instrument( 1 )Bar( 2 )To fixator( 4 )Implantation material( 3 ),Especially pedicel screw( 3 ),Including a coupling unit( 5 )Instrument( 1 )It is coupled to implantation material( 3 ),Especially head( 4 )Pedicel screw( 3 ),It further include a screw rod( 7 ),It is equipped with an external screw thread( 6 )With can be axially with respect to the coupling unit( 5 ),It and further include at least one internal whorl section( 12,13 ),The mode of an axial restraint is set to relative to coupling unit( 5 )It can be located at radially with respect to screw rod( 7 )With prestressing force screw rod( 7 )Direction,Pass through prestress component( 29,30 )Apply radial force,Wherein internal thread segment( 12,13 )It can be brought into and be engaged with it and be detached from,External screw thread( 6 )Screw rod( 7 )Due to radial positioning,Wherein screw rod( 16 )Screw thread flank( 7 )With screw thread side( 17 )Internal thread segment( 12,13 ),Two groups of sides are towards each other,Respectively it is formed with undercutting.
