Sonic screw

1 . A screw for fixation of a fracture comprising:

a shaft having a distal end, a proximal end, and a central axis;

a through bore extending along the central axis of the shaft;

a first outer thread located at the distal end;

a radially outwardly extending collar mounted on the shaft adjacent the shaft having the proximal end;

a second outer thread formed on the collar; and

an inner tool engagement portion at the proximal end.

2 . The screw according to claim 1 , wherein an outer diameter of the second outer thread is greater as an outer diameter of the shaft, the collar forming a smooth transition between the shaft and the second outer thread.

3 . The screw according to claim 1 , wherein the inner tool engagement portion is formed to fit with a hexagonal or torx screw driver.

4 . The screw according to claim 1 , wherein a step in the inner diameter of the through bore is formed adjacent the distal end of the shaft, so that a polymer pin inserted into the through bore of the shaft can be supported by the step.

5 . The screw according to claim 1 , wherein the screw further comprises a radial opening at the distal end of the screw.

6 . The screw as set forth in claim 1 wherein a surface of the collar facing the distal end is part-spherical in shape.

7 . A system for installation of a screw comprising:

a screw having a distal end, a proximal end, and a central axis;

a driving tool adapted to engage with the inner tool engagement portion of the screw; and

a hollow tissue protection sleeve adapted to engage with the second outer thread of the screw, and adapted to partially accommodate the driving tool.

8 . The system as set forth in claim 7 wherein the screw includes a radially outwardly extending collar located adjacent the proximal end of the screw, the collar having the second outer thread of the screw thereon.

9 . The system according to claim 7 , further comprising a polymer pin made of fluidizable material, adapted to be inserted into the axial through bore of the screw, and

an augmentation tool including a sonotrode for fluidizing the polymer material of the polymer pin, wherein the augmentation tool is adapted to be coupled with the proximal end of the tissue protection sleeve.

10 . A method of installation of a screw comprising:

a screw comprising a shaft having a distal end, a proximal end, and a central axis, a through bore extending along the central axis of the shaft, a first outer thread located at the distal end, a radially outwardly extending collar mounted on the shaft adjacent the shaft having the proximal end, a second outer thread formed on the collar, an inner tool engagement portion at the proximal end;

coupling a tissue protection sleeve to the outer thread on the collar at a proximal end of the screw;

engaging with a driving end of a driving tool into the inner engagement portion at the proximal end of the screw; and

installing the screw in an object.

11 . The method according to claim 10 , further comprising:

removing the driving tool;

inserting a polymer pin in the axial through bore of the screw;

positioning a sonotrode of an augmentation tool at the proximal end of the polymer pin;

fluidizing the material of the polymer pin;

pressing the fluidized material out of the screw to augment the screw in the object; and

removing the augmentation tool as well as the tissue protection sleeve.

12 . The method of claim 10 further comprising rotating the screw and tissue protection sleeve about an axis transverse to the central axis after the screw is installed.