Polyaxial Bone Fixation Element

Patent metadata

Field	Value
Publication number	US-2016367293-A1
Application number	US-201615254382-A
Country	US
Kind code	A1
Filing date	Sep 1, 2016
Priority date	Jul 20, 2007
Publication date	Dec 22, 2016
Grant date	—

Abstract

The present disclosure includes a polyaxial bone fixation element for use in spinal fixation to interconnect a longitudinal spinal rod with a patient's vertebra. The polyaxial bone fixation element preferably includes a bone anchor, a collet, a body, and a locking cap. The polyaxial bone fixation element preferably enables in-situ assembly. That is, the polyaxial bone fixation element 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. Accordingly, the polyaxial bone fixation element enables a surgeon to implant the bone anchor without the body to maximize visibility and access around the anchoring site. Once the bone anchor has been secured to the patient's vertebra, the body can be snapped-onto the bone anchor. The bone anchor preferably also includes a second tool interface so that a surgical instrument can be directly coupled to the bone anchor.

First claim

What is claimed:

1 . A polyaxial bone fixation element for coupling a longitudinal spinal rod to a vertebra, the bone fixation element comprising: a bone anchor including an enlarged, curvate head portion, wherein the head portion includes a first tool interface for engaging a first surgical instrument and a second tool interface for engaging a second surgical instrument, the first and second tool interfaces positioned in a head interface cavity; a body for interconnecting the bone anchor and the longitudinal spinal rod, the body having a longitudinal axis, an upper end with an upper opening, a lower end with a lower opening, a bore extending substantially between the upper opening and the lower opening, the bore having a first diameter D 1 , a rod-receiving channel for receiving the spinal rod located at the upper end, the rod-receiving channel having a channel axis that is oriented substantially perpendicular to the longitudinal axis, the body further including a lower edge portion adjacent the lower opening, the lower edge portion defining a second diameter D 2 smaller than the first diameter D 1 ; a collet including a first end, a second end and one or more slots extending from the second end, the slots defining a plurality of flexible arms, the collet movably positioned within the bore of the body; and a locking cap removably engageable with the body, the locking cap being movable from an unlocked position to a locked position wherein movement of the locking cap from the unlocked position to the locked position urges the rod against the collet and the flexible arms against the lower edge portion to secure a position of the bone anchor relative to the body.

2 . The polyaxial bone fixation element of claim 1 , wherein the drive recess includes a drive surface which is an internal surface formed in the head portion of the bone anchor for receiving an external tip formed on the first surgical instrument and the second tool interface is a plurality of threads formed on the head portion for threadably engaging a portion of the second surgical instrument.

3 . The polyaxial bone fixation element of claim 1 , wherein the second tool interface is located proximal of the first tool interface so that the second tool interface does not obstruct access to the first tool interface.

4 . The polyaxial bone fixation element of claim 1 , wherein the second surgical instrument is selected from one of a compressor, a distractor, a screw driver, a sleeve, minimally invasive instrumentation, a bone augmentation tool, an aspiration tool, a reduction tool, a coronal rotation tool, a tissue retractor and a kyphosis or lordosis correction tool.

5 . The polyaxial bone fixation element of claim 1 , wherein the body further includes an enlarged diameter portion, the enlarged diameter portion being located between the lower edge portion and the upper end, the enlarged diameter portion defining a third diameter D 3 , the third diameter D 3 being larger than the first diameter D 1 and the second diameter D 2 .

6 . The polyaxial bone fixation element of claim 5 , wherein the lower edge portion and the enlarged diameter portion each have a spherical concave surface.

7 . The polyaxial bone fixation element of claim 6 , wherein the collet is movably positioned within the bore of the body between a loading position wherein the collet is substantially aligned with the enlarged diameter portion so that the flexible arms of the collet can radially expand to receive the head portion of the bone anchor and a locked position wherein the collet is moved into contact with the lower edge portion so that the flexible arms compress against the head portion of the bone anchor to secure the position of the bone anchor with respect to the collet.

8 . The polyaxial bone fixation element of claim 7 , wherein the first spherical undercut has a radius of curvature r 1 and the flexible arms have an outer spherical surface having a radius of curvature r 2 , wherein r 1 is different than r 2 .

9 . The polyaxial bone fixation element of claim 1 wherein the collet includes a pair of longitudinal grooves on an outer surface and the body includes a pair of dimples extending into the bore and into the longitudinal grooves in an assembled configuration.

10 . A body assembly for snapping over a head portion of an implanted bone anchor and for interconnecting the bone anchor to an elongated spinal rod, the body assembly comprising: a body including a longitudinal axis, an upper end with an upper opening, a lower end with a lower opening, a bore extending between the upper and lower openings along a longitudinal axis, the bore having a first diameter D 1 proximate the upper opening and a rod-receiving channel extending from the upper end toward the lower end, the rod-receiving channel positioned on a channel axis that is oriented substantially perpendicular to the longitudinal axis, the bore includes a lower edge portion having a first spherical undercut terminating proximate the lower end and an enlarged diameter portion having a second spherical undercut disposed adjacent to the first spherical undercut toward the upper end, the lower edge portion having a second diameter D 2 and the enlarged diameter portion having a third diameter D 3 , the third diameter D 3 being larger than the first diameter D 1 , which is larger than the second diameter D 2 ; and a collet including a first end, a second end and at least two slots extending from the second end, the at least two slots defining flexible arms, the collet movably positioned within the bore of the body, wherein the flexible arms each have a root end, a terminal end and an outer curvate convex surface proximate the terminal end, the flexible arms rendering the collet expandable to accept the head of the bone anchor and compressible to secure the head of the bone anchor relative to the collet, wherein the flexible arms are positioned proximate the enlarged diameter portion in a loading position and at least a portion of the outer curvate convex surface of the flexible arms being in line contact with at least a portion of the first undercut in a locked position.

11 . The body assembly of claim 10 , further comprising a collet retention feature extending into the bore between the upper end and the second undercut that prevents the collet from passing through the upper opening in an assembled configuration.

12 . The body assembly of claim 11 , wherein the collet retention feature contacts a bottom end of a groove in the collet in the loading position to align the flexible arms with the second spherical undercut.

13 . The body assembly of claim 11 , wherein the body includes one or more partial passageways formed therein so that once the collet has been received within the bore of the body, a force is applied to the one or more partial passageways, thereby deforming the one or more partial passageways into one or more dimples extending into the bore of the body, the one or more dimples comprising the collet retention feature.

14 . The body assembly of claim 13 , wherein the one or more dimples interact with the collet to inhibit the collet from moving back through the upper opening formed in the body.

15 . A polyaxial bone fixation element for coupling a longitudinal spinal rod to a vertebra, the bone fixation element comprising: a bone anchor including a head portion, wherein the head portion includes a first tool interface for engaging a first surgical instrument and second tool interface for engaging a second surgical instrument, the first and second tool interfaces positioned in a head interface cavity; a body including

Assignees

• Depuy Synthes Products Inc

Inventors

• Keyer Thomas
• Capozzoli Joseph
• Mcdivitt Eric

Classifications

• A61B17/8841

  Tools specially adapted to engage a prosthesis · CPC title

• A61B17/7037 Primary

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

• A61B17/7076

  for driving, positioning or assembling spinal clamps or bone anchors specially adapted for spinal fixation · CPC title

• A61B17/7082

  for driving, i.e. rotating, screws or screw parts specially adapted for spinal fixation, e.g. for driving polyaxial or tulip-headed screws · CPC title

• A61B17/864

  hollow, e.g. with socket or cannulated · CPC title