Locking cap release mechanism

Patent metadata

Field	Value
Publication number	US-8998922-B2
Application number	US-201213679004-A
Country	US
Kind code	B2
Filing date	Nov 16, 2012
Priority date	Nov 16, 2012
Publication date	Apr 7, 2015
Grant date	Apr 7, 2015

Abstract

The present invention is directed to a release mechanism for removing and/or releasing a locking cap from the head of a bone anchor in situ. The release mechanism includes a sleeve, an anchor coupling member and a knob. The anchor coupling member is located within the sleeve and the knob engages both the anchor coupling member and the sleeve. The distal end of the sleeve and anchor coupling member engage the bone anchor causing the bone anchor to splay from the locking cap. A driver may be inserted into the central bore of the release mechanism to release any further threaded engagement of the locking cap and the bone anchor.

First claim

What is claimed is:

1. A release mechanism for releasing a locking cap threadingly engaged with a bone anchor head, the release mechanism including:
a sleeve comprising:
a sleeve bore extending along a longitudinal axis of the sleeve;
a distal end of the sleeve sized and configured to surround at least a portion of the locking cap and the bone anchor head, the distal end including a saddle portion, the saddle portion configured to abut a rod retained between the locking cap and the bone anchor head;

an anchor coupling member including:
a body portion having a proximal end that releasably mates with a knob, the body portion including an inner bore extending along a longitudinal axis of the anchor coupling member;
at least two arms extending from the body portion, each of the arms sized and configured to cover at least respective portions of the locking cap and the bone anchor head, each of the arms including a coupling feature at a distal end sized and configured to matingly engage a corresponding coupling feature of the bone anchor head;

the knob including:
a handle;
a knob body;
a knob bore extending through the handle and knob body along a longitudinal axis of the knob, the knob bore including a mating portion for releasably mating the knob with the anchor coupling member;

wherein the sleeve bore is sized and configured to receive at least a portion of the anchor coupling member and a portion of the knob body.

2. The release mechanism of claim 1 , wherein an outer surface of the sleeve includes a curved portion,
wherein the outer surface of the sleeve includes a tapered portion proximate the distal end of the sleeve.

3. The release mechanism of claim 1 , wherein an outer surface of the sleeve includes a cutout, the cutout having an elongated curvilinear shape in a direction along the longitudinal axis of the sleeve.

4. The release mechanism of claim 3 , wherein an end portion of the cutout defines a radius.

5. The release mechanism of claim 1 , wherein an outer surface of the sleeve includes a groove.

6. The release mechanism of claim 1 , wherein the saddle portion is sized and configured to fit between at least one of the arms and the rod,
wherein a first side and a second side of the saddle portion abuts a side of the at least one arm.

7. The release mechanism of claim 1 , wherein the sleeve bore includes a mating feature sized and configured to engage a corresponding mating feature on an outer surface of the knob body.

8. The release mechanism of claim 1 , wherein at least a portion of a surface of the sleeve includes a diamond-like carbon (DLC) coating.

9. The release mechanism of claim 1 , wherein the coupling feature of each of the arms include a slot sized and configured to engage a protrusion from an outer surface of the bone anchor.

10. The release mechanism of claim 9 , wherein the coupling feature of each of the arms further include a bottom edge sized and configured to engage a recessed portion in the outer surface of the bone anchor head.

11. The release mechanism of claim 1 , wherein at least one of the arms of the anchor coupling member includes a slot extending in a direction along the longitudinal axis of the anchor coupling member.

12. The release mechanism of claim 1 , wherein at least one of the arms of the anchor coupling member includes at least two slots in a direction along the longitudinal axis of the anchor coupling member;
wherein the length of each of the at least two slots is different.

13. The release mechanism of claim 1 , wherein the body portion of the anchor coupling member defines a circumferential perimeter greater than a circumferential perimeter defined by the arms such that a profile of the anchor coupling member tapers in the direction along the longitudinal axis of anchor coupling member.

14. The release mechanism of claim 1 , wherein the mating portion of the knob bore includes threads for releasably mating the knob with the anchor coupling member.

15. The release mechanism of claim 1 , wherein the handle of the knob includes a lobe portion.

16. The release mechanism of claim 1 , wherein the knob body includes a user indication to determine when the knob is not fully engaged within the sleeve.

17. A method of releasing a locking cap attached to a bone anchor, the method comprising:
assembling a release mechanism including:
inserting a portion of an anchor coupling member into a bore in a release sleeve;
aligning a side of a sleeve saddle portion with a side of a coupling feature of the anchor coupling member, where the sleeve saddle portion extends from a distal end of the release sleeve and the coupling feature extends from a distal end of the anchor coupling member;
attaching a knob to the anchor coupling member by inserting a portion of the knob into the release sleeve such that an inner bore of the knob matingly engages with the anchor coupling member;

attaching the coupling feature to a corresponding coupling feature on the bone anchor such that the sleeve saddle portion impacts a rod retained between the locking cap and the bone anchor and the coupling feature splays a side of the bone anchor from the locking cap.

18. The method of claim 17 , further comprising:
inserting a driver into a center bore of the release member to mate with a drive feature of the locking cap;
applying a rotational force to the driver to release a threaded engagement of the locking cap from the bone anchor.

19. The method of claim 17 , wherein attaching the coupling feature to the corresponding coupling feature on the bone anchor further comprises:
expanding the coupling feature over a head and side portion of the bone anchor to engage a recessed channel on the bone anchor.

20. The method of claim 17 , wherein attaching the knob to the anchor coupling member further comprises:
inserting the portion of the knob into the release sleeve such that a mating feature on an outer surface of the portion of the knob releasably mates with a corresponding mating feature located in the bore of the release sleeve.

Assignees

• Synthes Usa Llc
• Depuy Synthes Products Llc

Inventors

• Rutledge Henry

Classifications

• A61B17/7091

  for applying, tightening or removing longitudinal element-to-bone anchor locking elements, e.g. caps, set screws, nuts or wedges · CPC title

• A61B17/7032 Primary

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

• A61B17/7035

  Screws or hooks, wherein a rod-clamping part and a bone-anchoring part can pivot relative to each other · CPC title