USRE49138E1 - Ratcheted spinal devices - Google Patents

Abstract

A spinal device including a variable-length member including a ratchet mechanism that has an operative configuration that allows a change in length of the variable-length member in one direction and prevents a change in length of the variable-length member in an opposite direction, wherein the variable-length member includes polyaxial-joint attachment members for attachment to bone, which permit pivoting movement of the attachment members about more than one pivoting axis, characterized by a force applicator operative to adjust or advance the ratchet mechanism.

Description

FIELD OF THE INVENTION

The present invention relates generally to spinal implants and prostheses, and particularly to spinal implants having ratchet mechanisms, such as a spinal implant with joints that permit movement in different degrees of freedom, or a spinal implant with a force applicator to control a ratchet mechanism.

BACKGROUND OF THE INVENTION

Scoliosis is a spinal deformity affecting many people. Current surgical treatment involves affixing long fusion rods to the spine by pedicle screws. The rod system is intended to force the deformed spine into a more healthy position. Other spinal disorders which are often treated by fusion include hyperkyphosis and hyperlordosis.

As an alternative to fusion, PCT Patent Application PCT/US2011/035278 of the same inventor describes improved spinal devices that can be lengthened or shortened using a ratchet mechanism. The devices have a variable-length member that can be connected to standard pedicle screws as well as to other spinal rods, using appropriate connectors.

SUMMARY OF THE INVENTION

The present invention seeks to provide further improved spinal devices.

In one embodiment, the spinal device is in the form of a spinal rod (the term rod, or rod assembly, refers to one or more elongate components that together function as a rod and which do not necessarily have a cylindrical shape but can also be bars and other shapes) that can be lengthened or shortened using a ratchet mechanism. The rod is a variable-length member that can be connected to standard pedicle screws as well as to other spinal rods, using appropriate connectors. The variable-length member can also be directly connected to, or be supported by, bony elements of the spine.

In one embodiment of the invention, the device can be set to three different configurations:

a. Ratchet mechanism active and the variable-length member (rod) can change in length (extend or contract) in one direction.

b. Ratchet mechanism not active and the variable-length member can move in opposite directions corresponding to the extending and contracting directions.

c. Locked position, wherein the length of the variable-length member is fixed.

In an embodiment of the invention, the selection of these configurations can be done by rotating an internal element of the assembly. For example, the rotation of the internal element can be done using a worm gear mechanism. The worm gear can be activated by a shaft, through a percutaneous procedure or by an implantable mechanism such as an electric motor, magnet arrangement or other means known to those skilled in the art.

In another embodiment of the present invention, the variable-length member can have two portions with different rigidity. For example, the variable-length member can have a flexible portion (e.g., when the ratchet is built such that the rod can be only shortened) like a flexible cable, a rope, a flexible mechanical joint and other means known to those skilled in the art.

In another embodiment of the invention, useful when the rod is supported directly by bone structure of the spine, the hook holding against the bone can have a second hook to fix it to the optimal position.

BRIEF DESCRIPTION OF DRAWINGS

The present invention will be understood and appreciated more fully from the following detailed description, taken in conjunction with the drawings in which:

FIG. 1 is a simplified pictorial illustration of a ratcheted spinal device, constructed and operative in accordance with a non-limiting embodiment of the invention;

FIG. 2 is a simplified pictorial illustration of a ratchet mechanism of the ratcheted spinal device ofFIG. 1;

FIG. 3 is a simplified illustration of a force applicator that can adjust or advance the ratchet mechanism of the ratcheted spinal device ofFIG. 1;

FIG. 4 is a simplified pictorial illustration of a spinal device, including two rod assemblies that are connected between three vertebrae with three bone screws, constructed and operative in accordance with a non-limiting embodiment of the present invention, wherein there are connector assemblies that permit multiple degree-of-freedom movement;

FIG. 5 is a simplified top view illustration of one preferred embodiment of the connector assembly, in accordance with an embodiment of the present invention;

FIG. 6A is a simplified cross-sectional illustration of the embodiment ofFIG. 5; and

FIG. 6B is a simplified cross-sectional illustration of a modified version of the embodiment ofFIG. 5.

DETAILED DESCRIPTION OF EMBODIMENTS

Reference is now made toFIGS. 1-3, which illustrates a ratchetedspinal device10, constructed and operative in accordance with another non-limiting embodiment of the invention.

The ratchetedspinal device10 includes a variable-length member12. In the illustrated embodiment, the variable-length member12 is a rod. The term “rod” encompasses any slender element of any size and cross-sectional shape, such as but not limited to, a rod, bar, wire and the like.

As similarly described in PCT Patent Application PCT/US2011/035278,spinal device10 includes a ratchet mechanism14 (FIG. 2), which has an operative configuration that allows a change in length of variable-length member12 in one direction and prevents a change in length of the variable-length member12 in an opposite direction.Ratchet mechanism14 has ratchet teeth16 (FIG. 3; also called ratchet rack16) formed along an axial portion of variable-length member12, and a pawl18 (FIGS. 2-3) arranged to catch on one of theteeth16.Pawl18 extends from a controller element20 (FIG. 2) mounted about a pivot22 (FIG. 2) and provided with an eccentric cam24 (FIGS. 2-3). Rotation ofeccentric cam24 movespawl18 to one of three positions: a) in ratchet engagement withteeth16 so that variable-length member12 can incrementally move in one direction, b) in locked engagement withteeth16 so that variable-length member12 cannot move at all, and c) moved out of engagement withteeth16 so that variable-length member12 can move in both directions freely.

As seen inFIG. 1, oneend23 of variable-length member12 is arranged to linearly move through anaperture28 formed in ahousing30. Variable-length member12 includes two polyaxial-joint attachment members32. Both polyaxial-joint attachment members32 are used to attachdevice10 to available bone structure of the spine.

In contradistinction to PCT Patent Application PCT/US2011/035278, in the present invention,spinal device10 includes aforce applicator40 to controlratchet mechanism14.Force applicator40 includes, without limitation, acam42 which has a tooth44 (FIG. 3). Thehead46 ofcam42 is shown inFIG. 2 (e.g., hexagonal head);head46 is not shown for simplicity inFIG. 3. By turninghead46 with a suitable tool, such as a wrench (not shown), in the clockwise direction ofFIG. 3, thetooth44 ofcam42 forcefully moves ratchet rack16 (upwards in the sense ofFIG. 3), so that the tooth in whichpawl18 is engaged moves out of engagement withpawl18 and the next lower tooth ofratchet rack16 moves into engagement withpawl18. Accordingly,force applicator40 adjusts or advances theratchet mechanism14.

Reference is now made toFIG. 4, which illustrates aspinal device50, in accordance with an embodiment of the present invention.

In the illustrated embodiment,spinal device50 includes tworod assemblies52 that are connected between threevertebrae49 with threebone screws54. Therod assemblies52 may be constructed, without limitation, as ratchetedspinal devices10 or other spinal devices. Connector assemblies56 form jointed connections betweenrod assemblies52.Connector assemblies56 permit multiple degree-of-freedom movement of rod assemblies52 (e.g., variable-length members12), as will be explained below.

It is noted that any number of vertebrae can be selected, since the design of the system is modular. It is also noted that the middle jointed connection of the tworod assemblies52 does not have to be connected to any vertebra, meaning one or more vertebrae can be skipped, depending on the application. In the drawing figure,bone screws54 are inserted in the pedicles, but other insertion locations can be used.

Reference is now made toFIGS. 5 and 6A, which illustrate one preferred embodiment of theconnector assembly56, in accordance with an embodiment of the present invention.

Connector assembly56 includes a bolt58 (e.g., a central threaded bolt) having ahead60, and which passes through a hole formed in afirst hinge member62 and asecond hinge member64, which may lie on top of, or be adjacent to, firsthinge member62. Each hinge member is formed with a receiver66 (FIG. 6A) for receiving therein a pivot pin68 (FIG. 5). One of the pivot pins68 is pivotally received in anend70 of one of therod assemblies52, and theother pivot pin68 is pivotally received in anend72 of another of the rod assemblies52 (FIG. 5). Thusadjacent rod assemblies52 can pivot with respect to one another by means ofconnector assembly56. A locking element74 (such as a nut) securespins68 in place (FIG. 6A). Another locking element76 (such as a nut) is threaded on the end of threadedbolt58 to complete the assembly (FIG. 6A).

FIG. 6B illustrates a variation of the embodiment ofFIG. 6A. Like elements are designated by like numerals. The main differences are the shape of lockingelement74 and thereceiver66 of thefirst hinge member62 has a closed aperture instead of the open aperture ofFIG. 6A. Other variations are also possible within the scope of the invention.

Connector assemblies56 permit multiple degree-of-freedom movement ofrod assemblies52. Rotation is permissible about the longitudinal axis of central threadedbolt58, and independently about the longitudinal axis of eachpin68, which are perpendicular to the longitudinal axis of central threadedbolt58.

Claims (6)

What is claimed is:

1. A system comprising at least one spinal device, said at least one spinal device comprising:

a variable-length member comprising a ratchet mechanism that has an operative configuration that allows a change in length of said variable-length member in one direction and prevents a change in length of said variable-length member in an opposite direction, wherein said variable-length member comprises polyaxial-joint attachment members for attachment to bone, which permit pivoting movement of said attachment members about more than one pivoting axis, and

a force applicator operative to adjust or advance said ratchet mechanism, wherein said force applicator comprises a cam which has a tooth that engages a ratchet rack of said ratchet mechanism, and wherein by turning said cam, said tooth of said cam forcefully moves said ratchet rack so that a tooth of said ratchet rack, in which a pawl of said ratchet mechanism is engaged, moves out of engagement with said pawl and another tooth of said ratchet rack moves into engagement with said pawl.

2. The system according toclaim 1, wherein said at least one spinal device comprises a pair of said spinal devices and a connector assembly that forms a jointed connection between said pair of spinal devices that permits multiple degree-of-freedom movement of said pair of spinal devices.

3. The system according toclaim 2, further comprising a connector assembly that forms a jointed connection between said variable-length members that permits multiple degree-of-freedom movement of said variable-length members.

4. The system according toclaim 3, wherein said connector assembly comprises a bolt which passes through a first hinge member and a second hinge member adjacent said first hinge member, and pivot pins that pivotally connect said spinal devices to said first hinge member and said second hinge member.

5. The system according toclaim 4, wherein said connector assembly permits rotation about a longitudinal axis of said bolt, and independently about a longitudinal axis of each pivot pin, which are perpendicular to the longitudinal axis of said bolt.

6. The system according toclaim 1, wherein said cam of said force applicator comprises a head configured for turning with a tool.

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