Polyaxial bottom-loading screw and rod assembly

Patent metadata

Field	Value
Publication number	US-10154859-B2
Application number	US-201615084662-A
Country	US
Kind code	B2
Filing date	Mar 30, 2016
Priority date	Sep 29, 2008
Publication date	Dec 18, 2018
Grant date	Dec 18, 2018

Abstract

An anchor assembly for use in spinal fixation to interconnect a longitudinal spinal rod, which is integrally formed with a body of the anchor assembly. The anchor assembly includes a bone anchor, a collet, a body portion, a rod portion, and a locking cap. The anchor assembly is preferably configured so that in use, the bone anchor may be secured to the patient's vertebra prior to being received within the body portion. The anchor assembly enables a surgeon to implant the bone anchor without the body portion to maximize visibility and access around the anchoring site. Once the bone anchor has been secured to the patient's vertebra, the rod portion may be inserted into the rod-receiving channel of a second bone fixation element having a rod-receiving channel implanted at a second site and the body portion can be snapped-onto the bone anchor.

First claim

The invention claimed is:

1. A method of performing spinal fixation, the method comprising steps of:
implanting a bone anchor of a bone anchor assembly into a first vertebra;
implanting a bone fixation element having a rod-receiving channel into a second vertebra, spaced from the first vertebra along a first direction, such that a longitudinal axis of the rod-receiving channel extends along the first direction; and
coupling a body portion of the bone anchor assembly to the bone anchor and the bone fixation element such that (i) a head of the bone anchor is disposed in a bore of the body portion that extends through the body portion from an upper end of the body portion to a lower end of the body portion in a distal direction, and (ii) a fixation rod that is monolithic with the body portion is disposed in the rod-receiving channel of the bone fixation element,
wherein the coupling step comprises (1) receiving the head of the bone anchor in a collet that is disposed in the bore of the body portion in a loading position such that a plurality of arms that extend from a lower end of the collet toward an upper end of the collet radially expand so as to receive the head of the bone anchor and the plurality of arms are in vertical alignment with an enlarged portion of the bore that has a radius of curvature, and (2) moving the collet with the head within the bore to a locked position such that at least a portion of the flexible arms contact a lower spherical surface of the bore that is offset from the enlarged portion in the distal direction and that has a radius of curvature that is less than the radius of curvature of the enlarged portion.

2. The method of claim 1 , wherein the coupling step comprises inserting the fixation rod into the rod-receiving channel before receiving the head of the bone anchor in the bore of the body portion.

3. The method of claim 1 , wherein the coupling step comprises receiving the head of the bone anchor in the bore of the body portion before inserting the fixation rod into the rod-receiving channel.

4. The method of claim 1 , further comprising a step of attaching a locking cap to the bone fixation element so as to secure the fixation rod in the rod-receiving channel.

5. The method of claim 1 , wherein upon receiving the head of the bone anchor in the bore of the body portion, the bone anchor is polyaxially pivotable relative to the body portion, and the method further comprises a step of attaching a locking cap to the body portion such that the locking cap fixes a position of the bone anchor.

6. The method of claim 1 , comprising moving the collet from a loading position within the body portion, wherein the bone anchor is polyaxially pivotable relative to the body portion, to a locked position, wherein a position of the bone anchor is fixed relative to the body portion.

7. The method of claim 6 , wherein, in the locked position, the collet contacts an inner surface of the body portion causing the plurality of arms to compress against the head of the bone anchor.

8. The method of claim 1 , wherein the coupling step comprises receiving the fixation rod in the rod-receiving channel of the bone fixation element between a pair of arms of the bone fixation element that define the channel therebetween.

9. A body portion for a bone anchor assembly, the body portion comprising:
an upper end defining an upper opening, and a lower end spaced from the upper end along a first direction, the lower end defining a lower opening configured to receive a head of a bone anchor therethrough, the body portion defining a bore that extends through the body portion from the upper opening to the lower opening along a central axis that extends in the first direction, the bore having an enlarged portion, and a lower spherical surface that is spaced from the enlarged portion along the distal direction, the enlarged portion having a radius of curvature that is greater than a radius of curvature of the lower spherical surface, and at least a portion of the bore having a diameter that is greater than a diameter of the lower opening such that the body portion is configured to retain a collet within the bore between the upper end and the lower end; and
an elongate rod that is monolithic with the body portion and extends from the body portion along a direction that is angularly offset with respect to the central axis, the elongate rod having a length that is sized to extend from a first vertebra to a second vertebra, and the elongate rod being configured to be received in a rod-receiving channel of a bone fixation element.

10. The body portion of claim 9 , wherein the body portion is devoid of a rod-receiving channel that extends through the body portion between the upper end and the lower end.

11. The body portion of claim 9 , wherein the body portion includes an inner surface that at least partially defines the bore, and the inner surface defines internal threading configured to threadedly engage a locking cap.

12. The body portion of claim 9 , wherein the elongate rod extends from the body portion along a direction that is perpendicular to the first direction.

13. The body portion of claim 9 , wherein the elongate rod is configured to be received in the rod-receiving channel of the bone fixation element between a pair of arms of the bone fixation element that define the channel therebetween.

14. A bone anchor assembly comprising:
the body portion of claim 9 ; and
a collet configured to be retained in the bore of the body portion, the collet defining an upper end, and a lower end spaced from the upper end of the collet along the first direction, the lower end configured to expand so as to receive the head of the bone anchor.

15. The bone anchor assembly of claim 14 , wherein the collet is movable within the bore from an unlocked position, wherein the bone anchor is polyaxially pivotable relative to the body portion, to a locked position, wherein a position of the bone anchor is fixed relative to the body portion.

16. The bone anchor assembly of claim 15 , wherein the collet is configured such that, in the locked position, the collet contacts an inner surface of the body portion causing the lower end of the collet to compress against the head of the bone anchor.

17. The bone anchor assembly of claim 15 , further comprising a locking cap configured to engage internal threads of the bore of the body portion, wherein movement of the locking cap within the bore causes movement of the collet from the unlocked position to the locked position.

18. The bone anchor assembly of claim 15 , wherein the elongate rod extends from the body portion along a longitudinal axis that is perpendicular to the central axis, and the longitudinal axis extends through the collet when the collet is in at least one of the unlocked position and the locked position.

Assignees

• Depuy Synthes Products Inc

Inventors

• Keyer Thomas
• Mcdivitt Eric
• Capozzoli Joseph
• Wolf Boyd A

Classifications

• A61B17/7007

  Parts of the longitudinal elements, e.g. their ends, being specially adapted to fit around the screw or hook heads · CPC title

• A61B17/7037 Primary

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

• A61B2017/681

  Alignment, compression, or distraction mechanisms · CPC title

• A61B17/86

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

• A61B17/70 Primary

  Spinal positioners or stabilisers, e.g. stabilisers comprising fluid filler in an implant · CPC title