Expandable screw with separate expansion fingers

A screw, comprising:

• a shank (10), wherein a thread helix receiving groove (12) that winds around the shank (10) is disposed in the shank (10);
• and
• a thread helix (20) which is disposed in the thread helix receiving groove (12);
• wherein the thread helix (20) has an expandable helix section (25);
• wherein the shank (10) has, at the thread helix receiving groove (12), a wedge flank (41) for radially expanding the expandable helix section (25) as the shank (10) is moved relative to the expandable helix section (25);
• wherein the expandable helix section (25) comprises a helical back (27) and a plurality of expansion fingers (30) that project axially from the helical back (27) towards the wedge flank (41), wherein the helical back (27) interconnects the plurality of expansion fingers (30), and wherein the wedge flank (41) of the thread helix receiving groove (12) is configured for radially displacing the plurality of expansion fingers (30) outwardly as the shank (10) is moved relative to the plurality of expansion fingers (30);
• wherein at least some of the plurality of expansion fingers (30) are thread-engaging expansion fingers (31) which each comprise a thread engagement element (37) which radially protrudes on the respective thread-engaging expansion finger (31) and wherein the wedge flank (41) of the thread helix receiving groove (12) is configured for radially displacing the thread engagement elements (37) outwardly as the shank (10) is moved relative to the thread-engaging expansion fingers (31).