The screw (12) has a shank (13) with a bone-thread section and head (14)..The screw is joined to a rod-shaped element (40) by a holder part (1). The wall of the screw's tubular shank has a number of cavities (18) in. The end (16) of the shank facing the head has an internally threaded section, and the head has a corresponding external thread. The end of the shank facing the head has a section free of thread (20).