INSTRUMENT FOR PLACING A BONE SCREW, NOTABLY A SO CALLED "POLYAXIAL" SCREW OF VERTEBRAL OSTEOSYNTHESIS EQUIPMENT

• US 20100249798A1
• Filed: 11/05/2008
• Published: 09/30/2010
• Est. Priority Date: 11/05/2007
• Status: Abandoned Application

• Current Assignee: Medicrea International
• Original Assignee: Medicrea International
• Inventors: Ryan, David, Sournac, Denys
• Application Number:
  US12/741,210
• Publication Number:
  US 20100249798A1
• Time in Patent Office: Days
• US Class Current: 606/104
• CPC Class Codes: A61B 17/7076 for driving, positioning or assembling spinal clamps or bone anchors specially adapted for spinal fixation
• CPC Class Codes: A61B 17/8877 characterised by the cross-section of the driver bit
• CPC Class Codes: A61B 2090/031 torque limiting

Abstract

This instrument (1) includes a first component (3) intended to engage with the threaded proximal portion of the screw, a second component (2) intended to engage with the threaded distal portion of the screw, and means (4) for driving the first component (3) into rotation relatively to the second component (2). The driving means (4) include an actuation member (26, 27) for performing the driving into rotation. According to the invention, the actuation member (26, 27) is rotationally bound to the first member (3) via releasable connection means (33, 36), being released beyond a torque threshold exerted on this actuation member (26, 27) in the direction of rotation corresponding to the mounting of the screw on the instrument (1).

Claims

1. - An instrument (1) for placing a bone screw including a distal threaded portion, notably a so-called “

polyaxial”

screw of vertebral osteosynthesis equipment, comprising;

a first component (3) intended to engage with the threaded proximal portion of the screw,

a second component (2) intended to engage with the threaded distal portion of the screw, and

means (4) for driving the first component (3) into rotation relatively to the second component (2), so that, in a direction of rotation corresponding to the mounting of the screw on the instrument (1), said first component (3) may be brought so as to engage with the threaded proximal portion of the screw, and the screw to engage with said second component (2), these driving means (4) comprising an actuation member (26, 27) for performing said driving into rotation;

wherein said actuation member (26, 27) is rotationally bound to said first member (3) via releasable connection means (33, 36), being released beyond a torque threshold exerted on this actuation member (26, 27) in the direction of rotation corresponding to the mounting of the screw on the instrument (1).

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.