Bone screw

1. A bone screw, comprising:

a screw head and a threaded shank, wherein an axial bore into which a plurality of radial bores open which are set at a distance from each other, extends through the threaded shank, wherein said axial bore is open at the screw head side end and wherein the radial bores are also open at the radially outer end, wherein the axial bore is closed in an axial direction in the area of the end of the threaded shank that is located opposite the screw head;

an adapter that can be fitted onto the screw head and comprises an axial bore aligned with the axial bore of the threaded shank when the adapter is in the fitted state, the adapter comprising a holder having an inner circumferential shoulder for taking up a lower syringe or cartridge end in a tight manner inside the holder; wherein the adapter comprises an upper end and a lower end facing the screw head and the holder comprises a tubular portion extending from the upper end to the inner circumferential shoulder, wherein the inner circumferential shoulder is a tapered portion that converges inside the holder from the tubular portion toward the lower end of the adapter the tapered portion having a greater slope than an adjacent portion of the tubular member; and

wherein the adapter comprises a further circumferential shoulder having a tapered cross section that engages an outer surface of the screw head in the fitted state.

2. The bone screw according to claim 1 , wherein the adapter is made of a plastic material.

3. The bone screw according to claim 1 , wherein the screw head comprises a holder and the lower end of the adapter is designed complementarily with the holder.

4. The bone screw according to claim 1 , wherein an outer contour of the adaptor is formed complementary with an inner contour of an opening at the screw head.

5. A bone screw, comprising a screw head and a threaded shank, wherein an axial bore into which a plurality of radial bores open which are set at a distance from each other, extends through the threaded shank, wherein said axial bore is open at the screw head side end and wherein the radial bores are also open at the radially outer end, wherein the axial bore is closed in an axial direction in the area of the end of the threaded shank that is located opposite the screw head and wherein an aperture cross-section of the various radial bores is increasing towards the end of the threaded shank that is located opposite the screw head and wherein the axial bore in the threaded shank comprises at least one eccentric radial extension that extends over the length of the axial bore.

6. The bone screw according to claim 5 , characterized in that the radial bores open into the eccentric extension of the bore.

7. A bone screw, comprising a screw head and a threaded shank, wherein an axial bore into which a plurality of radial bores open which are set at a distance from each other, extends through the threaded shank, wherein said axial bore is open at the screw head side end and wherein the radial bores are also open at the radially outer end, wherein the axial bore is closed in an axial direction in the area of the end of the threaded shank that is located opposite the screw head and wherein the axial bore in the threaded shank comprises at least one eccentric radial extension that extends over the length of the axial bore.

8. The bone screw according to claim 7 , characterized in that the radial bores open into the eccentric extension of the bore.

9. A method of attaching a bone screw to a bone or vertebrae, the bone screw comprising a screw head and a threaded shank, wherein an axial bore into which a plurality of radial bores open which are set at a distance from each other, extends through the threaded shank, wherein said axial bore is open at the screw head side end and wherein the radial bores are also open at the radially outer end, wherein the axial bore is closed in an axial direction in the area of the end of the threaded shank that is located opposite the screw head and wherein an aperture cross-section of the various radial bores is increasing towards the end of the threaded shank that is located opposite the screw head, the method comprising:

screwing the threaded shank into a bone or vertebrae; and

injecting bone cement in the axial bore from the screw head side and from the axial bore through the radial bores of increasing size towards the end of the shank into the bone.

10. The bone screw according to claim 9 , wherein the radial bores are uniformly distributed both in axial and in circumferential direction.

11. The bone screw according to claim 9 , wherein the radial bores end between the thread flanks of the threaded shank.