Polyaxial bone anchor assembly with one-piece closure, pressure insert and plastic elongate member

• US 20080319490A1
• Filed: 08/20/2008
• Published: 12/25/2008
• Est. Priority Date: 09/30/2005
• Status: Active Grant

• Current Assignee: Roger P. Jackson
• Original Assignee: Roger P. Jackson
• Inventors: Jackson, Roger P.
• Granted Patent: US 8,353,932 B2
• Time in Patent Office: Days
• US Class Current: 606/308
• CPC Class Codes: A61B 17/7008 with parts of, or attached to, the longitudinal elements, bearing against an outside of the screw or hook heads, e.g. nuts on threaded rods A61B17/7007 takes precedence
• CPC Class Codes: A61B 17/701 Longitudinal elements with a non-circular, e.g. rectangular, cross-section A61B17/7005, A61B17/7007 take precedence
• CPC Class Codes: A61B 17/702 having a core or insert, and a sleeve, whereby a screw or hook can move along the core or in the sleeve
• CPC Class Codes: A61B 17/7022 Tethers, i.e. longitudinal elements capable of transmitting tension only, e.g. straps, sutures or cables A61B17/702 takes precedence
• CPC Class Codes: A61B 17/7029 the entire longitudinal element being flexible
• CPC Class Codes: A61B 17/7031 made wholly or partly of flexible material
• CPC Class Codes: A61B 17/7032 Screws or hooks with U-shaped head or back through which longitudinal rods pass
• CPC Class Codes: A61B 17/7035 Screws or hooks, wherein a rod-clamping part and a bone-anchoring part can pivot relative to each other
• CPC Class Codes: A61B 17/7037 wherein pivoting is blocked when the rod is clamped
• CPC Class Codes: Y10T 29/49826 Assembling or joining

Abstract

A medical implant assembly includes a polyaxial bone anchor having a shank, a receiver, a lower compression insert with planar surfaces for closely receiving an elongate connecting member with planar surfaces and a one-piece closure structure. The connecting member is made from a polymer. The closure structure engages both the connecting member and the insert with the engagement between the closure structure and the insert securely locking the polyaxial mechanism even if the connecting member exhibits creep.

Claims

1. In a medical implant assembly having at least one polyaxial bone screw attached to a longitudinal connecting member, the improvement wherein:

a) the connecting member is at least partially deformable; and

further comprising;

b) a compression insert engaging directly on the longitudinal connecting member and also engaging directly on a bone screw shank of the polyaxial bone screw, the insert having one of a lower planar connecting member seating surface and a lower radiused seating surface.

2. The improvement of claim 1 further comprising at least one recess formed in the compression insert, the recess receiving material flow of the longitudinal connecting member.

3. The improvement of claim 2 wherein the at least one recess is formed in one of a pair of planar side surfaces disposed adjacent to the lower seating surface.

4. The improvement of claim 3 wherein the at least one recess is a pair of recesses with one recess being formed in each of the pair of planar side surfaces.

5. The improvement of claim 1 wherein the receiver has structure cooperating with the compression insert, the structure directly engaging the insert and aligning a connecting member receiving channel of the insert with a through channel of the receiver.

6. The improvement of claim 5 wherein the structure directly engaging the insert is a first structure being at least one of a first pressure tab and a first groove, the insert having a second structure being at least one of a second groove cooperating with the first pressure tab and a second pressure tab cooperating with the first groove.

7. In a medical implant assembly having at least one polyaxial bone screw attached to a longitudinal connecting member, the improvement comprising:

a) a compression insert having a first planar bottom surface engaging a second planar bottom surface of the longitudinal connecting member, the connecting member being made from a polymer and having a top planar surface; and

b) a one-piece closure structure having a third planar bottom surface in direct contact with both the compression insert and the top planar surface of the connecting member.

8. The improvement of claim 7 further comprising at least one recess formed in the compression insert, the recess receiving material flow of the longitudinal connecting member.

9. In a polyaxial bone screw having a shank in pivotal relationship with a receiver, a channel for receiving a longitudinal connecting member and a closure top, the improvement comprising:

an insert having a base, opposed flanges and a plurality of planar surfaces for receiving and engaging planar surfaces of the longitudinal connecting member, the insert base being in direct engagement with the bone screw shank and the flanges being in direct engagement with the closure top.

10. The improvement of claim 9 further comprising at least one recess formed in the compression insert adjacent to at least one flange, the recess receiving material flow of the longitudinal connecting member.

11. The improvement of claim 10 wherein the at least one recess is a pair of opposed recesses, each recess formed near one of the flanges.

12. The improvement of claim 9 further comprising a groove formed in at least one of the flanges, the groove receiving a portion of the bone screw receiver.

13. The improvement of claim 12 wherein the portion of the bone screw receiver is a spring tab.

14. In a polyaxial bone anchor assembly having a closure top, a bone screw shank and a receiving member that receives a pressure insert, a longitudinal connecting member, the closure top and the shank, the improvement wherein:

the closure top is of single piece construction and the closure top directly engages both the longitudinal connecting member and a pair of upright arms of the pressure insert, the pressure insert directly engaging both the connecting member and the bone screw shank.

15. The improvement of claim 14 wherein the longitudinal connecting member is made from a deformable plastic.