Modular pedicle screw with multi-part cam lock structure

Patent metadata

Field	Value
Publication number	US-10973553-B2
Application number	US-201916373589-A
Country	US
Kind code	B2
Filing date	Apr 2, 2019
Priority date	Apr 2, 2018
Publication date	Apr 13, 2021
Grant date	Apr 13, 2021

Abstract

A modular pedicle screw assembly has a multi-part cam lock structure for fixing a threaded shank to a head subassembly. A modular pedicle screw assembly provides capture and release of a spherical end of a threaded shank by a head through rotation of closures radially disposed in an internal chamber of the head. Geometry of the closures cooperate with geometry of the internal chamber, providing a selective cam action between the closures and the internal chamber to increase and decrease size of an opening formed by the closures. Closure rotation produces an open state where the spherical end of the threaded shank can pass through the closures, releasing the spherical end of the threaded shank from the head, and a closed state where the spherical end of the threaded shank cannot pass through the closures thereby capturing the spherical end of the threaded shank in the head.

First claim

What is claimed is:

1. A pedicle screw for holding a spine rod in a fixed spatial orientation relative to a vertebra, the pedicle screw comprising:
a shank having an externally threaded shaft defining a distal end and a proximal spherical end having a configured socket;
a head having a top, a bottom, a bore extending from the top to the bottom and defining a circumferential wall, a central axis, a top opening, a bottom opening, and an interior with a radial wall, a chamber formed in the interior proximate the bottom opening, the chamber having a circumferential surface radially inset from the radial wall, the circumferential surface having a plurality of curved protrusions extending radially inward toward the central axis, each one of the plurality of curved protrusions circumferentially spaced from one another;
a plurality of closures equal in number to the plurality of curved protrusions and disposed in radial series in the chamber of the head, each closure having a curved body with a top surface, a first end, a second end, an inside surface, an outside surface, a first flange extending from the top surface proximate the first end, a second flange extending from the top surface proximate the second end, a third flange extending from the top surface between the first flange and the second flange, a first width extending from the first end to proximate the second end, a second width extending from the second end to the first width proximate the second end, and a sloping surface extending between the first width and the second width, the plurality of closures situated in the chamber of the head, wherein rotation of the closures provides capture and release of the spherical end of the shank by the head through cam action between the closures and the internal chamber to increase and decrease size of an opening formed by the closures; and
a cylindrical ring disposed in the bore of the head axially above the chamber, and having an outer circumference, a top, a bottom, and a plurality of notches in the bottom and spaced about the outer circumference and configure to receive first, second, and third flanges of the plurality of closures in radial series in the chamber, whereby rotation of the ring rotates the plurality of closures in radial series in the chamber to provide capture and release of the spherical head of the shank by the plurality of closures.

2. The pedicle screw assembly of claim 1 , wherein the first flange of each closure of the plurality of closures has a first height, the second flange of each closure of the plurality of closures has a second height that is equal to the first height, and the third flange of the each closure of the plurality of closures has a third height that is taller than the first and second heights.

3. The pedicle screw assembly of claim 2 , wherein the first flange of each closure of the plurality of closures has a first depth that extends from the inside surface to the outside surface, the second flange of each closure of the plurality of closures has a second depth that extends from the inside surface to the outside surface, and the third flange that has a third depth that extends from the outside surface to a middle of the top surface that is between the outside surface and the inside surface.

4. The pedicle screw assembly of claim 3 , wherein:
the circumferential wall of the head has a first trough extending from the top of the head to proximate the chamber of the head, and a second trough extending from the top of the head to proximate the chamber of the head, the first and second troughs defining a spine rod holder; and
the cylindrical ring has a first depression in the top, and a second depression in the top, the first and second depressions defining a second spine rod holder;
wherein when the second spine rod holder of the cylindrical ring misalign with the spine rod holder of the head, the closures are in an open state, and when the second spine rod holder of the cylindrical ring aligns with the spine rod holder of the head, the closures are in a closed state.

5. The pedicle screw assembly of claim 1 , wherein the interior chamber has a bottom ledge that receives each bottom of the plurality of closures.

6. The pedicle screw assembly of claim 1 , wherein:
the circumferential surface of the chamber has an upper end defined by a radially inward undercut and a bottom ledge; and
each one of the curved protrusions axially extends from upper end to the bottom ledge.

Assignees

• Life Spine Inc

Inventors

• Samuel Forrest
• Palagi Gregory

Classifications

• A61B17/8605

  Heads, i.e. proximal ends projecting from bone · CPC title

• A61B17/7037

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

• A61B17/7032 Primary

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