Polyaxial bone anchor with helical capture connection, insert and dual locking assembly

Patent metadata

Field	Value
Publication number	US-RE46431-E
Application number	US-201414460607-A
Country	US
Kind code	E1
Filing date	Aug 15, 2014
Priority date	Jun 18, 2003
Publication date	Jun 13, 2017
Grant date	Jun 13, 2017

Abstract

A medical implant assembly includes a polyaxial bone anchor having a shank, a receiver, a lower compression insert with surfaces for closely receiving an elongate connecting member and a dual closure structure that may include a single flange or helical flange. The dual closure structure independently engages the connecting member and the lower compression insert. A threaded capture connection of the bone anchor includes a shank upper surface exclusively engaging the lower compression insert and a retainer threadably attached to the shank and spaced from the upper surface, the retainer configured for polyaxial motion with respect to the receiver prior to locking.

First claim

What is claimed and desired to be secured by Letters Patent is as follows:

1. A polyaxial bone anchor comprising:
a) a shank having a body for fixation to a bone and an integral upper portion, the upper portion having an upper end surface and an outer surface with a first helically wound guide and advancement structure thereon;
b) a receiver having a top portion and a base, the receiver top portion defining an open channel, the base having a seating surface partially defining a cavity, the channel communicating with the cavity, the cavity communicating with an external of the base through an opening sized and shaped to receive the shank upper portion therethrough;
c) a compression insert disposed in the receiver, the insert having a mating surface exclusively frictionally engageable with the upper end surface of the shank upper portion; and
d) a retainer having an external surface and a central bore with an internal surface defining the central bore having a second helically wound guide and advancement structure thereon, the first helically wound guide and advancement structure configured to rotatably mate with the second helically wound guide and advancement structure to secure the retainer to the shank upper portion within the receiver, the shank upper portion and the retainer being in fixed relation to one another, both the upper portion and the retainer being in swivelable relation within the receiver, providing selective angular positioning of the shank with respect to the receiver, the retainer external surface being in slidable engagement with the receiver seating surface, the retainer being substantially spaced from the compression insert at any and all angular positions of the shank with respect to the receiver.

2. The bone anchor of claim 1 wherein the compression insert mating surface is concave and the shank upper end surface is convex.

3. The bone anchor of claim 1 wherein the receiver seating surface is at least partially spherical and the retainer external surface is at least partially spherical.

4. The bone anchor of claim 1 wherein the shank upper portion has a tool engagement formation formed thereon adapted for non-slip engagement by a tool for driving the bone screw shank body into bone.

5. The bone anchor of claim 1 wherein the shank upper portion has a flared portion disposed adjacent the first guide and advancement structure, the retainer having a cooperating surface abutting against the flared portion when the first guide and advancement structure is fully mated with the second guide and advancement structure.

6. The bone anchor of claim 1 further comprising a closure structure insertable into the receiver, the closure structure for operably urging the insert into fixed frictional engagement with the bone screw shank upper portion and moving the shank in a direction to frictionally lock the position of the retainer with respect to the receiver, thereby locking the shank body in a selected angle with respect to the receiver.

7. The bone anchor of claim 1 wherein the compression insert has a seating surface and first and second upstanding arms, the arms operatively receiving a longitudinal connecting member; and further comprising a two-piece closure having an outer fastener and an inner set screw, the outer fastener directly engaging the first and second arms of the compression insert and independently locking the shank with respect to the receiver, the outer fastener having an outer flange in interlocking engagement with a flange track of the receiver, the inner set screw biasing the longitudinal connecting member toward the compression insert seating surface.

8. The bone anchor of claim 7 wherein the flange is a helical flange.

9. The bone anchor of claim 7 wherein the flange is a first flange and further comprising a second, opposed flange.

10. The bone anchor of claim 9 wherein the outer fastener has first and second opposed upper wings frictionally engaged with top surfaces of the receiver.

11. The bone anchor of claim 1 further comprising resilient structure extending from the receiver and biasing against the compression insert at a depression formed in a surface of the insert, the resilient structure prohibiting rotational movement of the compression insert within the receiver.

12. The bone anchor of claim 11 wherein the resilient structure is a pair of opposed spring tabs attached to the receiver and extending toward a central axis of the receiver.

13. The bone anchor of claim 1 wherein the compression insert is a lower compression insert and further comprising an upper compression insert disposed in the receiver, a longitudinal connecting member being closely received between the lower and upper inserts.

14. The bone anchor of claim 13 wherein the upper compression insert is attached to a closure structure.

15. In a polyaxial bone screw assembly for surgical implantation and including a shank having an upper end and a threaded body for inserting into a bone, a receiver having an outward opening channel adapted to receive a longitudinal connecting member within the channel, the receiver having a shank receiving opening, and a closure structure also being received in the receiver for locking the assembly, the improvement comprising:
(a) a first helical guide and advancement structure located on the shank spaced from the upper end;
(b) a retainer having an outer surface and an inner substantially cylindrical surface, the outer surface being in swivelable sliding engagement with the receiver prior to locking of the assembly with the closure structure, the inner surface having a second helical guide and advancement structure thereon, the inner surface at least partially defining a central through bore of the retainer, the second guide and advancement structure sized and shaped to receive and mate with the first guide and advancement structure to fix the retainer to the shank with the retainer being spaced from the upper end; and
(c) a compression insert engaging the shank upper end and spaced from the retainer at any and all angular positions of the retainer with respect to the receiver.

16. The improvement of claim 15 wherein the closure structure operably urges the compression insert into fixed frictional engagement with the bone screw shank upper end and moves the shank in a direction to frictionally lock the position of the retainer with respect to the receiver, thereby locking the shank in a selected angle with respect to the receiver.

17. The improvement of claim 15 wherein the compression insert has a seating surface and first and second upstanding arms, the arms operatively receiving a longitudinal connecting member and wherein the closure structure is a two-piece closure structure having an outer fastener and an inner set screw, the outer fastener directly engaging the first and second arms of the compression insert and independently locking the shank with respect to the receiver, the outer fastener having an outer flange in interlocking engagement with a flange track of the receiver, the inner set screw biasing the longitudinal connecting member toward the compression insert seating surface.

18. The improvement of claim 17 wherein the flange is a helical flange.

19. The improvement of claim 17 wherein the flange is a first flange and further comprising a second, opposed flange.

20. The improvement of claim 19 wherein the outer fastener has first and second opposed upper wings frictionally engaged with top surfaces of the receiver.

Assignees

• Jackson Roger P

Inventors

• Jackson Roger P

Classifications

• A61B2560/0406

  specially shaped apparatus housings · CPC title

• A61B17/7037 Primary

  wherein pivoting is blocked when the rod is clamped · CPC title

• A61B17/7032 Primary

  Screws or hooks with U-shaped head or back through which longitudinal rods pass · CPC title

• A61B17/86

  Pins or screws {or threaded wires; nuts therefor (A61B17/72 take precedence)} · CPC title