System for performing spinal arthrodesis via the posterior approach at the level of a facet joint

Abstract

Title: System for performing a spinal arthrodesis via the posterior approach at a facet joint The system for performing a spinal arthrodesis via the posterior approach at a facet joint comprises an implant device (1) and its retaining means (2). The implant device (1) is in the form of an element comprising an opening (12) for receiving a bone graft, and is intended to be introduced into a cavity (5) previously made at the location of the facet joint to be immobilized, while the retaining means is in the form of a compression screw (2), its pitch at the proximal part (21) being less than that of the distal part (20), and the transverse dimensions of which allow it to pass into the opening (12), while the proximal (21) and distal (20) parts are each screwed into one of the articular processes to be connected.Figure for abstract: Fig. 1.

Description

Title of the invention: System for performing spinal arthrodesis via the posterior route at the level of a facial joint

[0001] The present invention relates to a system for performing spinal arthrodesis via the posterior route at the level of a facet joint, said system comprising an implant device and its retaining means.

[0002] Such an intervention, carried out by the posterior approach, makes it possible to immobilize two vertebrae by fusing each of the lower articular processes of a vertebra with the upper articular process opposite the neighboring lower vertebra through the insertion into the interface space of a cage-type implant device containing a bone graft.

[0003] In practice, the surgeon prepares the implant location by removing the joint capsule using 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, joint space, to the straight shape of the implant, and to promote the subsequent fusion of the facets through the implant by having bled / revived the facets until reaching the cancellous bone.

[0004] Implant devices are already known for carrying out such an intervention, which consist of a wedge-shaped element, the two opposite faces of which, each intended to come into contact with a facet, have a surface provided with reliefs to ensure anchoring, and which is pierced with a multiplicity of holes intended for the development of the bone material after deposition of a bone graft. However, the wedge shape, despite the reliefs, tends not to prevent expulsion, so these implant devices are associated with at least one screw, passing through said implant device through a hole and screwed into an apophysis obliquely relative to the median plane of the implant. Document WO 2012154653 describes such an implant device, provided with two screws.However, due to the low inclination of the screw axes, these are practically parallel to the said median plane, so that there is little bone material between the screws and the walls of the facets, which are then weakened, and consequently the fixation is less certain.

[0005] Also known from document WO2019016341 in the name of the present Applicant is an implant device which is in the form of a flat element, of constant thickness, comprising, for receiving a bone graft, a large central opening giving it a substantially annular shape, and intended to be introduced into a cavity previously made at the location of the facet joint to be immobilized, said element having a D shape, the rounded side constituting the distal edge of insertion into said cavity, while the opposite, rectilinear proximal edge, comprises a means of securing to a holding and positioning tool, while the opposite faces of said flat element, comprise reliefs which consist of notches arranged perpendicular to the direction of insertion, each of the notches having a tooth profile with two sides, one of which, the one oriented towards said proximal edge, is perpendicular or substantially perpendicular to the main plane of said element, while the other side is inclined.

[0006] The constant thickness is intended to overcome the disadvantages of a wedge shape and, in association with the notches, to prevent expulsion, and thus to eliminate the use of screws.

[0007] However, despite this, it has been found that expulsion could occur.

[0008] The aim of the present invention is to propose a system for performing spinal arthrodesis via the posterior route at the level of a facet joint, comprising an implant device and its retaining means, making it possible to avoid expulsion, without resorting to screws for fixing said implant device in the bone material, as well as to optimize its maintenance.

[0009] The system for performing a spinal arthrodesis by the posterior route at the level of a facet joint comprising an implant device and its retaining means according to the invention, is characterized in that said implant device is in the form of an element comprising, for receiving a bone graft, at least one opening or notch open on the proximal side and closed on the distal side, and intended to be introduced into a cavity previously made at the location of the facet joint to be immobilized, the opposite faces of said element, comprising reliefs, and in that said retaining means is in the form of a compression screw, namely that its thread is not constant, and more particularly that this pitch is at the level of the proximal part less than that of the distal part, said screw being of transverse dimensions allowing it to pass into said opening or notch,so as to allow the passage in the latter of said compression screw, while said proximal and distal parts are each screwed into one of said articular processes to be connected.

[0010] It will be understood that after introduction of the implant into the cavity previously made at the location of the facet joint to be immobilized, a hole is made in the apophyses passing through said implant through its opening or its notch, then the compression screw is screwed into it and is then trapped in the opening or behind the distal closure of the notch, thus preventing movement in the direction of expulsion. In addition to retaining the implant, the compression screw generates the rap close to the two apophyses and the clamping of said implant, so as to increase its primary anchoring and promote bone fusion.

[0011] According to an additional characteristic of the system according to the invention, the implant device is in the form of a flat element, of constant thickness.

[0012] According to an alternative embodiment of the system according to the invention, the implant device has a curved shape.

[0013] Such a shape is intended to adapt to the curvature of the facet joint, without it being necessary to significantly rectify the interface space.

[0014] According to another additional characteristic of the system according to the invention, the implant device has flexibility characteristics.

[0015] This feature allows the implant device to adapt to the curvature of the facet joint, whether or not it is curved.

[0016] According to another additional characteristic of the system according to the invention, the reliefs of the opposite faces of the implant device consist of notches arranged perpendicular to the direction of introduction, each of the notches having a tooth profile with two sides, one of which, the one oriented towards the proximal edge, is perpendicular or substantially perpendicular to the main plane of said implant device.

[0017] According to another additional characteristic of the system according to the invention, the implant device comprises a single opening, giving it a substantially annular shape.

[0018] According to a variant of the system according to the invention, the implant device has a U shape, delimiting between its two branches a notch, the transverse part connecting the two branches being positioned on the distal introduction side.

[0019] According to another additional characteristic of the system according to the invention, the compression screw comprises between the two proximal and distal parts, a smooth section.

[0020] According to another additional characteristic of the system according to the invention, the proximal part of the compression screw has a diameter greater than that of the distal part.

[0021] According to another additional characteristic of the device according to the invention, the threads of the proximal and distal parts of the compression screw each comprise a tapping notch.

[0022] The advantages and characteristics of the system according to the invention will emerge more clearly from the description which follows and which refers to the attached drawing, which represents a non-limiting embodiment thereof.

[0023] In the attached drawing:

[0024] [Fig-1] represents a perspective view of a system according to the invention.

[0025] [Fig.2] represents a schematic sectional view of the same system implemented between two apophyses.

[0026] [Fig.3] represents a schematic sectional view of the same system, under another angle, according to arrow A in [Fig.2].

[0027] With reference to [Fig. 1], it can be seen that the system according to the invention comprises an implant device 1 and a screw 2.

[0028] The implant device 1 shown consists, without limitation, of an implant device conforming to that described in document WO2019016341, namely that it is in the form of a substantially flat element, and which has the shape of a D, intended to be introduced between two apophyses to replace the joint capsule. It thus comprises an introduction side, distal 10, of rounded shape and a rectilinear proximal side 11, as well as a central opening 12 which gives it a generally annular shape.

[0029] On the other hand, each of its two faces 13 and 14, of which only face 13 is visible in this [Fig.l], is provided with notches 15 aligned transversely with respect to the introduction axis, and intended for the creation of an anchoring in the bone material.

[0030] The screw 2 consists of a compression screw, which for this purpose has a thread of non-constant pitch, that is to say that it comprises a threaded distal part 20 and a proximal part 21 also threaded, separated by a smooth section 22, while the pitch of the thread of the proximal part 21 is smaller than the pitch of the thread of the distal part 20. On the other hand, it can be seen that the diameter of the screw 2 is smaller than the dimensions of the opening 12.

[0031] It will be noted that the smooth section 22 is optional, it can be replaced by a threaded transition zone, allowing passage from one pitch to another.

[0032] It will also be noted that the threads of the distal 20 and proximal 21 parts are preferably provided with tapping notches, respectively 23 and 24. Furthermore, the proximal part 21 has a diameter greater than that of the distal part 20, so that its thread cuts a different thread in the bone material from that cut upstream by the thread of the distal part 20.

[0033] Referring now to Figures 2 and 3, one can see the installation of the system according to the invention, at the level of one of the two facet joints of two vertebrae, and more particularly, seen posteriorly, the joint between the left apophysis 3 of a vertebra and the left apophysis 4 of the adjacent vertebra positioned below. Knowing that the right side is treated in an identical manner.

[0034] In previous steps not shown, the two apophyses 3 and 4 are prepared, namely that the joint capsule as well as the osteophytes have been removed, then the facet joint space is opened to provide a cavity 5 at the level of the interface space which is further revived by means of a rasp until reaching the spongy bone in order to prepare a good subsequent fusion.

[0035] In Figures 2 and 3, the implant 1 has been introduced into the cavity 5 in the direction of the arrow B, and it fits tightly into it.

[0036] It should be noted that from a technical operating point of view, the introduction of implant 1 on the right side is carried out simultaneously on the left side, knowing that in the case of successive introductions, the first introduction would tend to close the interface space on the other side.

[0037] It will also be noted that before the introductions, a bone graft G will have been placed in the opening 12.

[0038] It can also be seen in these figures that the installation of the implant 1 is completed by that of the screw 2, knowing that a hole will have been previously drilled in the lower apophysis 4 then in the upper apophysis 3, passing through the opening 12 of the implant 1, possibly with a sighting device.

[0039] The screw 2 is then screwed into this hole, which on the one hand prevents the expulsion of the implant 1, but also, due to the difference in pitch of the threads of the distal 20 and proximal 21 parts, allows the processes 3 and 4 to be tightened on the implant 1 and more particularly the notches 15 thereof, and thus ensures perfect support and promotes bone fusion.

[0040] In Figures 2 and 3, the screw 2 is perfectly perpendicular to the main plane of the implant 1, this is however a special case since the insertion axis of the screw 2 can perfectly make an angle with this plane. The drilling being carried out blindly after introduction of the implant 1, the opening 12 preferably, but not limited to, has large dimensions compared to the transverse dimensions of the screw 2, so as to leave a large latitude when a sighting device is not used.

[0041] It will also be noted that, to the extent that a high-performance aiming device can be used, it may be envisaged that the opening 12 can be tapped, in order to allow screwing of the distal part 20, the thread of which is then extended and total or partial replacement of the smooth section 22.

Claims

Claims

1. System for performing a spinal arthrodesis by the posterior route at a facet joint comprising an implant device (1) and its retaining means (2), characterized in that said implant device (1) is in the form of an element comprising, for receiving a bone graft (G), at least one opening (12) or a notch open on the proximal side and closed on the distal side, and intended to be introduced into a cavity (5) previously made at the location of the facet joint to be immobilized, the opposite faces (13, 14) of said element comprising reliefs (15), and in that said retaining means is in the form of a compression screw (2), namely that its thread is not constant, and more particularly that the pitch is at the proximal part (21) less than that of the distal part (20),said screw (2) being of transverse dimensions allowing it to pass into said opening (12) or notch, so as to allow the passage into the latter of said compression screw (2), while said proximal (21) and distal (20) parts are each screwed into one of the articular processes (3, 4) to be connected.,

2. System according to claim 1, characterized in that the implant device (1) is in the form of a flat element of constant thickness.

3. System according to claim 1, characterized in that the implant device (1) has a curved shape.

4. System according to any one of claims 1 to 3, characterized in that the implant device (1) has flexibility characteristics.

5. System according to any one of claims 1 to 4, characterized in that the reliefs of the opposite faces (13, 14) of the implant device (1) consist of notches (15) arranged perpendicular to the direction of introduction (B), each of the notches (15) having a tooth profile with two sides, one of which, the one oriented towards the proximal edge (11), is perpendicular or substantially perpendicular to the main plane of said implant device (1).

6. System according to any one of claims 1 to 5, characterized in that the implant device (1) has a single opening (12), giving it a substantially annular shape.

7. System according to any one of claims 1 to 5, characterized in that the implant device (1) has a U shape, delimiting between its two branches a notch, the transverse part connecting the two branches being positioned on the distal introduction side.

8. System according to any one of claims 1 to 7, characterized in that the compression screw (2) comprises between the two proximal (21) and distal (20) parts, a smooth section (22).

9. System according to any one of claims 1 to 8, characterized in that the proximal part (21) of the compression screw (2) has a diameter greater than that of the distal part (20).

10. System according to any one of claims 1 to 9, characterized in that the threads of the distal (20) and proximal (21) parts of the compression screw (2) each comprise a tapping notch (23, 24).

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