Instrument for placing a bone screw, notably a so called "polyaxial" screw of vertebral osteosynthesis equipment

2- The instrument (1) according to claim 1, wherein the releasable connection means comprise:

• a first series of teeth (33) laid out on said first component (3) or on a part (25) integral with this first component (3);
• a second series of teeth (36) laid out on the actuation member (26, 27), and
• holding means (28) capable of maintaining the teeth (33, 36) of both of these series of teeth, in engagement with each other until said tightening torque is reached and allowing these teeth to be disengaged when the tightening torque is reached.

3- The instrument (1) according to claim 2, wherein said maintaining means comprise an elastic member (28) normally maintaining the teeth (33, 36) engaged with each other and the elastic deformation of which allows the teeth to become disengaged.

4- The instrument (1) according to claim 2 wherein

• said first series of teeth (33) is laid out in the proximal end of said first component (3) or on a part (25) integral with this first component;
• said actuation member (26, 27) has the shape of a bushing which will cap the proximal end of the first component (3) or of said part (25) integral with this first component, comprising a bottom in which said second series of teeth (36) is laid out, and
• said proximal end or said part (25) and said bushing form respective abutment surfaces (32, 35) between which a spring (28) is interposed, forming said maintaining means.

5- The instrument (1) according to claim 4, wherein

• said part (25) forms a shoulder (22) forming a first abutment surface;
• and
• the actuation member (26, 27) comprises an external part (27) including said bottom and comprising a tapped peripheral wall and an inner part (26) comprising a threaded peripheral wall and an internal shoulder (35) forming a second abutment surface.

6- The instrument (1) according to claim 5, wherein said inner part (26) forms a distal housing receiving an O-ring gasket (29) opposing the inflow of fluids into the interior of the actuation member (26, 27).

7- The instrument (1) according to claim 1, wherein said first component (3) comprises a distal tube, the distal end of which is tapped in order to engage with the proximal threaded portion of the screw, this tube being connected on the proximal side, to a proximal part (25), coaxial therewith, comprising said first series of teeth (33) laid out in its proximal end.

8- The instrument (1) according to claim 1, wherein said second component (2) comprises a distal tubular portion (5) in which said first component (3) is engaged and a cage-shaped proximal portion (6) delimiting a housing in which said actuation member (26, 27) is found.