IMPLANT DEVICE FOR PERFORMING POSTERIOR SPINAL ARTHRODESIS AT A FACET JOINT, AND SYSTEM COMPRISING THE IMPLANT AND ITS POSITIONING TOOL

Abstract

The implant device for performing posterior spinal arthrodesis at a facet joint is in the form of a flat element of constant thickness. The element has reliefs on each of its faces so as to form an anchor associated with at least one complementary anchor, such as a screw with a diameter greater than the thickness of the element. The complementary anchor can be screwed into the flat element such that at least some of its threads protrude from the faces. The element has a U-shape with a transverse part from which two branches extend. On the proximal side, the free ends of the branches have retention devices, on the inner side of the U so as to permit the screwing and insertion of the screw between the branches.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

See Application Data Sheet.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

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THE NAMES OF PARTIES TO A JOINT RESEARCH AGREEMENT

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INCORPORATION-BY-REFERENCE OF MATERIAL SUBMITTED ON A COMPACT DISC OR AS A TEXT FILE VIA THE OFFICE ELECTRONIC FILING SYSTEM (EFS-WEB)

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STATEMENT REGARDING PRIOR DISCLOSURES BY THE INVENTOR OR A JOINT INVENTOR

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BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an implant device for performing posterior spinal arthrodesis at a facet joint, and a system comprising said implant device and its positioning tool.

2. Description of Related Art Including Information Disclosed Under 37 CFR 1.97 and 37 CFR 1.98

Spinal arthrodesis involves fusing two vertebrae to immobilize them.

The posterior route is the easiest, using either an osteosynthesis plate or bar that connects the vertebrae and is fastened thereto by means of pedicle screws, or interbody cages of the type described, for example, in documents US 2011/230965, FR 2 946 245 and WO 02/03895, designed to be placed in the intervertebral space after removal of the vertebral disc.

Two vertebrae can also be immobilized using a posterior approach, by fusing each of the lower articular processes of one vertebra with the upper articular process of the neighboring lower vertebra.

This posterior approach to spinal arthrodesis of a facet joint offers a number of advantages over other commonly used techniques, including less trauma and fewer risks.

However, this technique requires the use of different means from those used in other operating techniques, and in particular cages with different characteristics from those used in the aforementioned documents.

In particular, such a cage needs to have a certain thinness, given the narrowness of the space into which it has to be introduced. As a result, the main difficulty lies in securing that cage.

Implant devices for insertion in a facet joint are already known, in particular the one described in document WO 2012154653, which consists of a wedge-shaped element whose two opposite faces, each intended to come into contact with a facet, having a surface provided with reliefs to anchor it, which is pierced by a multiplicity of holes designed for the development of bone material after deposition of a bone graft, while fastening is achieved by means of two screws, each screwed into a process, obliquely with respect to the median plane of the implant. This implant system remains complex, or more specifically, its implementation is complex.

Already known from document W02019016341 to the present Applicant is an implant in the shape of a flat element of constant thickness, comprising, in order to receive a bone graft, a large central opening which gives it a substantially annular shape, and which device is intended to be inserted into a cavity previously made at the location of the facet joint to be immobilized; said element being D-shaped and comprises a rounded side which constitutes the distal edge for being inserted into said cavity, while the opposite straight proximal edge comprises a means for securing to a holding and positioning tool; while the opposite surfaces of said flat element comprise reliefs which consist of reliefs arranged perpendicularly to the insertion direction, each of the reliefs having a tooth profile with two faces of which one, the face oriented on the side of said proximal edge, is perpendicular or substantially perpendicular to the main plane of said element, while the other face is inclined. The constant thickness prevents expulsion, as might occur when the cage is corner-shaped. And from an implementation point of view, the preparatory work for shaping the cavity is carried out as simply as possible, meaning that in the cavity, the opposing faces are flat and parallel.

In practice, the surgeon prepares the implant site by removing the joint capsule with an instrument called a facet chisel, then uses a rasp to “bleed” the parts opposite the joint space on the facets. This step with the rasp has two purposes: to prepare the pre-existing space, with a boneless but often slightly curved interline, for the straight shape of the implant, and to promote subsequent fusion of the facets through the implant that has bled/revived the facets down to the cancellous bone.

Also known from documents EP0912147 and WO9848738 are interbody implants for use in spinal surgery, designed to be placed in the intervertebral space and not in a facet joint.

These implants take the form of a cage wherein a screw can be journaled, at least part of which has a diameter greater than the thickness of said cage, so as to form anchoring means. Fitting such an implant requires extensive preparatory work, which is difficult to carry out on a facet joint.

In the case of the implant described in EP0912147, the screw is screwed into a threaded annular part located at the periphery of the cage, and therefore with an external diameter greater than the thickness of the cage, which requires special machining of the bone material to accommodate said annular part.

Document WO9848738 proposes a similar implant, with single or double tapered faces to adapt to the characteristics of vertebral bodies.

Although the bone anchoring means of these implants make it possible to dispense with the use of screws, introduced obliquely for example, none of these implants is suitable for posterior spinal arthrodesis at a facet joint, which exhibits installation constraints, because the space into which the implant must be introduced is of reduced dimensions, particularly in terms of thickness.

BRIEF SUMMARY OF THE INVENTION

The aim of the present invention is to remedy the various disadvantages mentioned above, by proposing an implant device, as well as a system comprising said implant and its positioning tool, for performing posterior spinal arthrodesis at a facet joint.

The implant device for performing posterior spinal arthrodesis at a facet joint, according to the invention, takes the form of a flat element of constant thickness, designed to be introduced into a cavity previously made at the location of the facet joint to be immobilized, comprising on each of its faces reliefs forming notches constituting anchoring means, and associated with at least one complementary anchoring means, consisting of a screw with a diameter greater than the thickness of said element, designed to be screwed into said flat element so that at least part of its threads protrude from said faces, and it is characterized in that it is U-shaped, i.e. it comprises a transverse part, from which extend two branches separated by a gap, and where said transverse part constitutes the distal edge for introduction into said cavity, while on the proximal side the free ends of said branches each comprise, on the inner side of the U, retention means capable of enabling said screw to be screwed in and inserted between said branches, and which project from each of the inner sides of said branches to extend into said space, without going beyond the thickness of said flat element.

The U-shape of the implant device, i.e. the fact that it is open on the proximal side, and that it does not comprise an annular element for retaining a screw, makes it possible to obtain an element, in addition to being thin, which does not require specific machining.

In addition, the screw axis is coaxial with the implant insertion axis, enabling a percutaneous approach to be envisaged.

The present invention also concerns a system for performing posterior spinal arthrodesis at a facet joint, comprising an implant device and its positioning tool, wherein said implant is in the form of a flat element of constant thickness, intended to be inserted into a cavity previously made at the location of the facet joint to be immobilized, comprising on each of its faces reliefs forming notches constituting anchoring means, and associated with at least one complementary anchoring means, consisting of a screw with a diameter greater than the thickness of said element, designed to be screwed into said flat element so that at least part of its threads protrude from said faces, and it is characterized in that:

• • said implant is U-shaped, i.e. it comprises a transverse part, from which two branches extend, and where said transverse part constitutes the distal edge for introduction into said cavity, while on the proximal side the free ends of said branches each comprise, on the inner side of the U, retention means that are able to permit the screwing and insertion of said screw between said branches,
  • said positioning tool comprises an assembly of coaxial parts, namely, firstly, a first part, one end of which is able to hold said flat element by holding it by the outside of its branches, secondly, a second part into which said first part is able to slide until the part thereof holding said flat element is extracted; thirdly, also inside said first part, a third part, one end of which is able to be connected to said flat element and to hold said screw facing said branches; and fourthly, inside said third part, a fourth part which consists of a rod, one end of which is configured to engage said screw and to be able to drive it in rotation through an action on the other end.

According to an additional feature of the system according to the invention, the end of the first part, designed to hold the flat element from the outside of its branches, comprises two parallel branches, designed to grip said branches from the outside.

According to another additional feature of the system according to the invention, the branches of the planar element each have a longitudinal guide groove on the outside for the branches of the first part, and in that the bottoms of said grooves and the inside of said branches have complementary reliefs capable of axially immobilizing said element between said branches when the latter are held externally in the second part.

According to a further feature of the system according to the invention, the reliefs consist of bosses.

According to a further feature of the system according to the invention, the third part is tubular in shape, while its end suitable for holding the screw in place consists of a cavity with a round, threaded cross-section.

According to a further feature of the system according to the invention, the tool comprises an additional part, usable in a percutaneous procedure, and integrating all the other parts.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

The advantages and features of the implant device according to the invention, as well as of the system for performing posterior spinal arthrodesis at a facet joint according to the invention, will become clearer from the following description, which refers to the appended drawing, which represents a non-limiting embodiment thereof.

FIG. 1 shows a schematic perspective view of a system according to the invention.

FIG. 2 shows a partial schematic exploded perspective view of the same system, including the implant device according to the invention.

FIG. 3 shows a schematic cross-sectional perspective view in a longitudinal plane of part of the same implant system and device.

FIG. 4 shows a schematic partial cross-sectional perspective view in a longitudinal plane of the same implant system and device.

FIG. 5 shows a partial perspective view of the same system.

FIG. 6 shows a perspective view of a part of the same system.

FIG. 7 shows a perspective view of another part of the same system.

FIG. 8 shows the implant of the same system after placement in a facet joint.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 shows a system for performing posterior spinal arthrodesis at a facet joint according to the invention, comprising an implant 1 and a tool 2 for positioning that implant 1.

Additionally, FIGS. 2, 3 and 4, show that the implant 1 takes the form of a flat element of constant thickness, generally U-shaped, thus comprising a transverse part 10 constituting the distal edge, from which extend two branches 11. The two branches 11 each have protruding elements 12 on the inside at their free end, forming a thread for screwing in a screw 3, and allowing this screw 3 to occupy the space 13 separating the two branches 11 once it has been screwed in.

Advantageously, but not in a limiting fashion, the distal edge 10 is tapered to facilitate insertion.

The implant 1 features tooth-shaped reliefs 15 on the two outer faces 14 of each of the two branches 11, to enable it to clamp into the bone material.

On the other hand, the screw 3 has a diameter greater than the thickness of the implant 1, more particularly between two faces 14, and more precisely, it is only the thread 30 of the screw 3, or part of it, that protrudes from the faces 14 of the implant 1.

It can also be seen on these figures that each of the branches 11 has a longitudinal groove 16 on the outside, i.e. on the side opposite that containing the projecting elements 12, extending along the entire length of the branch 11. In addition, the bottom 17 of each groove 16 features a concave boss 18.

Referring now to FIG. 8, an implant device 1 according to the invention can be seen positioned at the facet joint between vertebrae L5 and SI, the right side of which is shown in part, while the left side, not shown, is similarly equipped.

Prior to insertion, the bone material of both vertebrae is cut away at the facet joint to create a cavity C, shared between the two vertebrae, in this case L5 and SI, extending in the contact plane and of a thickness corresponding to that of implant 1. The implant device 1 is then inserted into the cavity C.

Once the screw 3 has been screwed in, the thread 30, which is advantageously self-tapping, penetrates the bone material to anchor the implant 1.

The small dimensions of cavity C, and therefore also those of the implant, can complicate its insertion, particularly in view of the different operations involved, i.e. introduction with impaction, followed by screwing. The tool 2, adapted to the implant 1, has been designed to facilitate this insertion, forming the system according to the invention.

The tool 2 is thus made up of a multiplicity of elongated, coaxial parts.

The tool 2 thus comprises a first tubular part 4, one end 40 of which is designed to hold the implant 1 by clamping the branches 11. To this end, it comprises two parallel branches 41, each designed to be housed in a groove 16 on the implant 1, in contact with the base 17, while convex bosses 42 are fitted into the concave bosses 18. The implant 1 is thus immobilized between the branches 41, both transversely by the branches 41 and by the grooves 16, and axially through the bosses 42 and 18.

The tool 2 also features a tubular second part 8, into which the first part 4 can slide axially, and which in its extreme position can constrain the branches 41 to hold the implant 1.

The tool 2 also features a third tubular part 6, slidably mounted in the second part 4. Its free end 60 has a threaded hole 61 wherein the screw 3 is engaged when in the waiting position.

Optionally, the end 60 of part 6 can be fitted with an axially projecting finger 62, designed to engage in a blind hole 19 at the end of a branch 11 of implant 1, for indexing the two threads 12 and 61.

It should also be noted that part 6 has a threaded end 63 at its end opposite the one containing the screw 3, onto which a nut 64 is screwed. FIG. 6 shows that tightening the nut 64 on the threaded end 63 moves the sleeve 8 on the part 4, thereby reinforcing the grip of the implant 1 via the branches 41.

The tool 2 comprises a fourth part 7, arranged in the part 6, which is intended to transmit a screwing torque to the screw 3, and which for this purpose has an end 70 with a male indentation 71 corresponding to the female indentation 31 of the screw 3, which in this case is hexagonal in cross-section.

It should be noted that the version of the system 2 described above is the most advanced version, although it is entirely possible that some of the parts may not be necessary depending on the procedure to be performed. This is the case for the part 5, which can be used primarily for percutaneous surgery, but which is not required for open surgery. For this purpose, at one end 50, it has two blade-like extensions 51 which, as can be seen more precisely in FIGS. 4 and 5, are positioned against and outside the parallel branches 41 to hold them in place.

Claims

1. An implant device for performing posterior spinal arthrodesis of a facet joint, comprises: a flat element, having constant thickness and comprising reliefs on each of its faces forming notches so as to form an anchoring means associated with at least one complementary anchoring means,

2. A system for performing posterior spinal arthrodesis at a facet joint, the system comprising: an implant device; anda positioning tool,

3. The system, according to claim 2, wherein the end of the first part, suitable for holding the flat element from the outside of its branches, comprises two parallel branches so as to grip said branches from the outside.

4. The system, according to claim 2, wherein the branches of the flat element each have a longitudinal guide groove on the outside for the branches of the first part, and wherein the bottoms of said grooves and the inside of said branches have complementary reliefs capable of axially immobilizing said element between said branches when the latter are held externally in the second part.

5. The system, according to claim 4, wherein the reliefs are comprised of bosses.

6. The system, according to claim 2, wherein the third part is tubular in shape, while its end suitable for holding the screw in place being comprised of a cavity with a round, threaded cross-section.

7. The system, according to claim 2, wherein the tool comprises an additional part, usable in a percutaneous procedure, and integrating all the other parts.