Polyaxial bone anchor with polymer sleeve
A bone anchor assembly comprising a shank, receiver, pressure insert, sleeve and closure. The sleeve having a body constructed of deformable material and including a transfer of non deformable material molded into the body of the sleeve to transfer force around the body. The receiver having interior guides and the insert having guide followers that cooperate to align the insert in the receiver and prevent rotation of the insert in the receiver.
1. A spinal implant sleeve adapted for connecting with a tensioned cord and placement in a channel of a bone anchor receiver and having a bore extending therethrough for receiving the tensioned cord; the sleeve having a sleeve body constructed of a non-rigid deformable polymer material, and a transfer structure constructed of a rigid non-deformable material having projections extending therefrom to resist torque of the transfer structure relative to the sleeve body, the transfer structure being incorporated into the sleeve body to receive a force from above the sleeve and transfer the force around the sleeve body of the sleeve.
2. The sleeve according to claim 1 , wherein the sleeve body is constructed of a thermoplastic polymer.
3. The sleeve according to claim 1 , wherein the sleeve body is constructed of a polyurethane material.
4. The sleeve according to claim 1 , wherein the sleeve body is constructed of PEEK.
5. The sleeve according to claim 1 , wherein the sleeve body is constructed of ultra-high molecular weight polyethylene.
6. The sleeve according to claim 1 , wherein the transfer structure is constructed of a patient implantable metal.
7. The sleeve according to claim 6 , wherein the transfer structure is constructed of a cobalt chrome alloy.
8. The sleeve according to claim 6 , wherein the transfer structure is constructed of a metal selected from titanium and titanium alloys.
9. A bone anchor comprising:
a) a receiver having a channel adapted to receive one of an elongate member and a tensioned cord;
b) a pressure insert positioned in the receiver and having upward extending arms and each of the arms having upper surfaces;
c) a sleeve positioned in the channel above the pressure insert, and in combination with the one of an elongated member and a tensioned cord; and
d) a closure that is positioned in the receiver above the sleeve,
wherein the sleeve includes a sleeve body constructed of a non-rigid deformable polymer and a transfer structure constructed of a rigid non-deformable metal; the transfer structure having depending legs with lower surfaces that align and mate with the upper surfaces on the pressure insert arms in an overlapping relationship for transferring force from the closure through the transfer structure to the pressure insert without transferring pressure directly through the deformable body of the sleeve to the insert, the transfer structure having projections extending therefrom and into the sleeve body to resist torque of the transfer structure relative to the sleeve body.
10. The anchor according to claim 9 , further comprising an implantable shank received in the receiver and receiving downward force from the insert.
11. The anchor according to claim 9 , wherein the transfer structure is constructed of an alloy selected from cobalt chrome and titanium alloys.
12. The anchor according to claim 9 , wherein the deformable polymer is selected from PEEK, PCU, graphite-filled polyurethane and ultra high molecular weight polyethylene.
13. The anchor according to claim 9 , wherein the receiver includes at least one internal vertical guide structure and the insert includes at least one guide follower structure that cooperates with the vertical guide structure to allow the insert to move vertically in the receiver, but prevents rotation of the insert relative to the receiver.
14. A bone anchor for supporting one of an elongate member and a tensioned cord in a U-shaped channel, the bone anchor comprising:
a receiver having a U-shaped channel adapted to receive one of an elongate member and a tensioned cord;
a pressure insert positioned in the receiver and having upward extending arms, with each of the arms having upper contact surfaces;
a sleeve positioned in the U-shaped channel above the pressure insert and having a circular bore extending therethrough to slidingly receive and surround the one of an elongated member and a tensioned cord; and
a closure that is positioned in the receiver above the sleeve,
wherein the sleeve includes a sleeve body constructed of a deformable polymer and a transfer structure constructed of a rigid metal, the transfer structure having depending legs with lower surfaces that align and mate with the upper contact surfaces on the pressure insert arms in an overlapping relationship for transferring force from the closure through the transfer structure to the pressure insert without transferring pressure directly through the deformable body of the sleeve to the insert.
15. The anchor according to claim 14 , wherein the transfer structure includes projections extending therefrom and into the sleeve body to resist torque of the transfer structure relative to the sleeve body.
16. The anchor according to claim 14 , wherein the rigid metal is selected form the group consisting of cobalt chrome alloys and titanium alloys.
17. The anchor according to claim 14 , wherein the deformable polymer is selected from the group consisting of PEEK, PCU, graphite-filled polyurethane and ultra high molecular weight polyethylene.