Locking compression members for use with bone anchor assemblies and methods

Patent metadata

Field	Value
Publication number	US-10987138-B2
Application number	US-201916403114-A
Country	US
Kind code	B2
Filing date	May 3, 2019
Priority date	Mar 14, 2013
Publication date	Apr 27, 2021
Grant date	Apr 27, 2021

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 surface of the bone. In an exemplary embodiment, a bone anchor assembly is provided that includes a bone anchor configured to engage bone, a receiver member for seating a head of the bone anchor, and a compression member for securing the bone anchor at fixed angle with respect to the receiver member when the compression member is seated within the receiver member. Corresponding engagement features of the compression member and the receiver member can be engaged in a secured configuration to inhibit or prevent removal of the compression cap from the receiver member and optionally to substantially prevent longitudinal and/or rotational movement of the compression member with respect to the receiver member.

First claim

The invention claimed is:

1. A method of assembling a bone screw, comprising:
passing a shank portion of the bone screw through an aperture formed in a distal end of a receiver member such that a head portion of the screw is seated in the receiver member; and
inserting a compression cap into the receiver member and engaging opposed projections extending radially outward from the compression cap with complementary recesses formed in the receiver member to retain the compression cap within the receiver member,
wherein inserting the compression cap comprises rotating the compression cap relative to the receiver member to move the opposed projections into engagement with the complementary recesses, and
wherein the complementary recesses are formed in a shelf that extends radially inward from an interior sidewall of the receiver member and said engaging comprises camming the opposed projections over ramped edges of the shelf and snapping the opposed projections into the complementary recesses.

2. The method of claim 1 , wherein said engaging is effective to maintain the compression cap in a substantially fixed longitudinal position relative to the receiver member.

3. The method of claim 1 , wherein said engaging is effective to maintain the compression cap in a substantially fixed rotational position relative to the receiver member.

4. The method of claim 1 wherein inserting the compression cap into the receiver member and engaging the opposed projections with the complementary recesses includes:
deflecting free ends of first and second arms of the compression cap inwards during assembly of the compression cap to the receiver member and then deflecting the free ends of the first and second arms outward when the compression cap is seated in the receiver member; and
engaging a ramped surface of the interior of the receiver member with ramped outer surfaces of the first and second arms of the compression cap.

5. A surgical method, comprising:
passing an elongate shank of a bone anchor in a proximal-to-distal direction through an aperture formed in a distal end of a receiver member such that a proximal head portion of the bone anchor is polyaxially seated in a spherical recess formed in a distal portion of the receiver member;
inserting a compression member between opposed arms of the receiver member proximal to the proximal head of the bone anchor such that opposed projections on an outer surface of the compression member engage with complementary recesses on an inner surface of the receiver member to prevent proximal movement of the compression member relative to the receiver member; and
wherein inserting the compression member comprises rotating the compression member relative to the receiver member to move the opposed projections into engagement with the complementary recesses, and
wherein the complementary recesses are formed in a shelf that extends radially inward from an interior sidewall of the receiver member and said rotating comprises camming the opposed projections over ramped edges of the shelf and snapping the opposed projections into the complementary recesses.

6. The method of claim 5 , wherein the opposed projections of the compression member and the receiver member are positioned such that, when inserted, the compression member applies a frictional force to the head of the bone anchor to maintain the bone anchor at a fixed angle with respect to the receiver member.

7. The method of claim 6 , further comprising applying a force sufficient to overcome the frictional force to adjust an angle of the bone anchor with respect to the receiver member.

8. The method of claim 5 , further comprising:
drilling an appropriately sized hole in a patient's bone; and
driving the bone anchor into the prepared hole using a driver tool.

9. The method of claim 5 , further comprising locating a spinal fixation element between the opposed arms of the receiver member proximal to the compression member.

10. The method of claim 9 , further comprising engaging a closure mechanism with an inner thread formed on the opposed arms of the receiver member proximal to the spinal fixation element to urge the compression member further distally to exert additional frictional force on the head of the bone anchor and lock the bone anchor at a fixed angle relative to the receiver member.

11. The method of claim 5 , wherein the complementary recesses features are effective to maintain the compression member in a substantially fixed longitudinal position relative to the receiver member.

12. The method of claim 5 , wherein the complementary recesses features are effective to maintain the compression member in a substantially fixed rotational position relative to the receiver member.

13. The method of claim 5 , wherein inserting the compression member includes:
deflecting free ends of first and second arms of the compression member inwards and then deflecting the free ends of the first and second arms outward to engage the engagement features of the compression member with the corresponding features of the receiver member; and
engaging a ramped surface of the interior of the receiver member with ramped outer surfaces of the first and second arms of the compression member.

Assignees

• Medos Int Sarl
• Medos Int Sari

Inventors

• Chandanson Thibault
• Quintanilha Ernest
• Spratt Frank
• Cormier Philip A

Classifications

• A61B2017/00526

  Methods of manufacturing · 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

• A61B17/7037 Primary

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

• A61B2017/00477

  Coupling (A61B2017/0046 takes precedence) · CPC title

• A61B17/7032

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