Bone anchor assemblies and methods with improved locking

Patent metadata

Field	Value
Publication number	US-2016128733-A1
Application number	US-201514966531-A
Country	US
Kind code	A1
Filing date	Dec 11, 2015
Priority date	Mar 14, 2013
Publication date	May 12, 2016
Grant date	—

Abstract

Various exemplary methods and devices are provided for fixing bone anchors to bone. In general, the methods and devices can allow for a bone anchor to be fixed to a bone at a desired angle to a receiver member. In an exemplary embodiment, a bone anchor assembly is provided that includes a bone anchor configured to engage bone, a receiver member that polyaxially seats a spherical head of the bone anchor, and a compression member seated within the receiver member, proximally of the head of the bone anchor. The compression member can have a distal end with gripping features thereon configured to create at least one line contact and/or one band contact with the head of the bone anchor, thus providing a firm grip on the head of the bone anchor and reducing a risk of slippage of the bone anchor with respect to the receiver member.

First claim

What is claimed is:

1 - 18 . (canceled)

19 . A bone anchor assembly, comprising:
a bone anchor having a proximal head portion and a distal shank portion; a receiver member having a polyaxial seat formed therein for polyaxially seating the head portion of the bone anchor; and a compression member configured to be disposed within the receiver member, the compression member having a tooth formed on a distal-facing surface thereof that extends around an entire circumference of the distal-facing surface such that a crest of the tooth is configured to make a ring-shaped line contact with the head portion of the bone anchor.

20 . The bone anchor assembly of claim 19 , wherein the tooth extends around the entire circumference of the distal-facing surface of the compression member in a plane that is perpendicular to a longitudinal axis of the compression member.

21 . The bone anchor assembly of claim 19 , wherein the tooth extends around the entire circumference of the distal-facing surface of the compression member in a plane that is at a non-perpendicular angle to a longitudinal axis of the compression member.

22 . The bone anchor assembly of claim 19 , wherein the compression member includes an outer cylindrical sidewall surface and an inner cylindrical sidewall surface, and the distal-facing surface extends therebetween.

23 . The bone anchor assembly of claim 19 , wherein the distal-facing surface is shaped as a negative of the proximal head portion of the bone anchor.

24 . The bone anchor assembly of claim 19 , wherein the distal-facing surface is spherically shaped.

25 . The bone anchor assembly of claim 19 , wherein a largest diameter of the crest of the tooth is smaller than a diameter of the proximal head portion of the bone anchor.

26 . The bone anchor assembly of claim 19 , wherein the tooth includes two planar, substantially perpendicular sidewalls that meet at the crest.

27 . The bone anchor assembly of claim 19 , wherein the tooth is the only feature formed on the distal-facing surface.

28 . The bone anchor assembly of claim 19 , wherein a proximal portion of the compression member includes a pair of spaced apart arms defining a U-shaped seat for receiving a spinal fixation element.

29 . The bone anchor assembly of claim 19 , further comprising a set screw having an outer thread configured to engage an inner thread formed on the receiver member such that the set screw can contact a proximal portion of the compression member as it is threaded into the receiver member.

30 . The bone anchor assembly of claim 29 , wherein the set screw includes a central passage from a top surface thereof to a bottom surface thereof, the central passage including an inner thread configured to engage an outer thread of a second set screw.

31 . A bone anchor assembly, comprising:
a bone anchor having a proximal head portion and a distal shank portion; a receiver member having a polyaxial seat formed therein for polyaxially seating the head portion of the bone anchor; and a compression member configured to be disposed within the receiver member, the compression member having a gripping feature formed on a distal-facing surface thereof that is configured to grip the proximal head portion of the bone anchor with greater friction as compared to a distal-facing surface formed as a negative of the proximal head portion of the bone anchor.

32 . The bone anchor assembly of claim 31 , wherein the gripping feature extends around an entire circumference of the distal-facing surface of the compression member.

33 . The bone anchor assembly of claim 32 , wherein the gripping feature extends around the entire circumference of the distal-facing surface of the compression member in a plane that is perpendicular to a longitudinal axis of the compression member.

34 . The bone anchor assembly of claim 32 , wherein the gripping feature extends around the entire circumference of the distal-facing surface of the compression member in a plane that is at a non-perpendicular angle to a longitudinal axis of the compression member.

35 . The bone anchor assembly of claim 31 , wherein the compression member includes an outer cylindrical sidewall surface and an inner cylindrical sidewall surface, and the distal-facing surface extends therebetween.

36 . The bone anchor assembly of claim 31 , wherein the distal-facing surface is shaped as a negative of the proximal head portion of the bone anchor.

37 . The bone anchor assembly of claim 31 , wherein the distal-facing surface is spherically shaped.

38 . The bone anchor assembly of claim 31 , wherein the gripping feature is the only feature formed on the distal-facing surface.

39 . A bone anchor assembly, comprising:
a bone anchor having a proximal spherically-shaped head portion and a distal shank portion; a receiver member having a polyaxial seat formed therein for polyaxially seating the head portion of the bone anchor; and a compression member configured to be disposed within the receiver member, the compression member having a distal-facing spherically-shaped surface configured to receive the head portion of the bone anchor, the distal-facing surface including a single tooth formed thereon that extends around an entire circumference thereof such that a crest of the tooth is configured to make a ring-shaped line contact with the head portion of the bone anchor.

Assignees

• Depuy Synthes Products Inc

Inventors

• Spratt Frank
• Cormier Philip A
• Quintanilha Ernest
• Dziedzic Sara
• Pavento Nicholas
• SHAW Derek
• Chandanson Thibault

Classifications

• A61B17/7032 Primary

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

• A61B17/7037 Primary

  wherein pivoting is blocked when the rod is clamped · 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

• A61B2090/037

  with a frangible part, e.g. by reduced diameter · CPC title