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

Abstract

Title: System for performing a spinal arthrodesis via a posterior approach at the level of a facet joint The system for performing a spinal arthrodesis via a posterior approach at the level of a facet joint comprises an implant device (1) and its retention 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 retention means is in the form of a compression screw (2), its pitch at the level of the proximal part (21) being less than that of the distal part (20), and whose transverse dimensions allow it to pass through 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 the summary: Fig. 1.

Description

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

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

[0002] Such an intervention, performed via a posterior approach, makes it possible to immobilize two vertebrae by fusing each of the inferior articular processes of one vertebra with the superior articular process opposite the neighboring inferior vertebra through the insertion in the interface space of a cage-type implant device containing a bone graft.

[0003] In practice, the surgeon prepares the implant site by removing the joint capsule using an instrument called a facet joint chisel, then uses a rasp to "bleed" the areas adjacent to the joint space on the facets. This rasp step has two purposes: to prepare the pre-existing space, with a joint space free of bone but often slightly curved, 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 down to the cancellous bone.

[0004] Implant devices for performing such a procedure are already known. These devices consist of a wedge-shaped element, the two opposite faces of which, each intended to come into contact with a facet, have a surface with raised features to ensure anchoring. The wedge is also pierced with multiple holes to allow for bone growth after the placement of a bone graft. However, despite the raised features, the wedge shape tends not to prevent expulsion. Therefore, these implant devices are associated with at least one screw, which passes through a hole in the implant device and is screwed into a process obliquely to the median plane of the implant. Document WO 2012154653 describes such an implant device equipped with two screws.However, due to the slight inclination of the screw axes, they are practically parallel to the 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] Document WO2019016341 filed on behalf of the present Applicant also discloses an implant device 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 introduction into said cavity, while the opposite edge, proximal straight, includes a means of attachment to a holding and positioning tool, while the opposite faces of said flat element have reliefs which consist of notches arranged perpendicular to the direction of introduction, each of the notches having a two-sided tooth profile, 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 eliminate the need for the use of screws.

[0007] However, despite this, it was found that an eviction could occur.

[0008] The present invention aims to provide a system for performing spinal arthrodesis via a posterior approach at the level of a facet joint, comprising an implant device and its retention 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 via a posterior approach at the level of a facet joint, comprising an implant device and its retention 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 having reliefs, and in that said retention means is in the form of a compression screw, namely that its thread is non-constant, and more particularly that this thread pitch is lower at the proximal part than at the distal part, said screw having transverse dimensions enabling it to pass through said opening or notch,in order to allow the passage of said compression screw through the latter, 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 the implant is inserted into the cavity previously created at the location of the facet joint to be immobilized, a hole is drilled through the apophyses, passing through the implant via its opening or notch. The compression screw is then screwed in and trapped within 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 proximity of the two apophyses and the clamping of said implant, so as to increase its primary anchorage and promote bone fusion.

[0011] According to an additional feature 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 for adaptation to the curvature of the facet joint, without the need to significantly rectify the interface space.

[0014] According to another additional feature 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 feature 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 two-sided tooth profile, 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 feature of the system according to the invention, the implant device has 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 arms a notch, the transverse part connecting the two arms being positioned on the distal side of introduction.

[0019] According to another additional feature 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 feature 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 feature of the device according to the invention, the threads of the proximal and distal parts of the compression screw each have a tapping notch.

[0022] The advantages and characteristics of the system according to the invention will become clearer from the following description, which relates 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 cross-sectional view of the same system installed between two apophyses.

[0026] [Fig.3] represents a schematic cross-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, shaped like a D, intended to be inserted between two apophyses to replace the joint capsule. It thus comprises a distal insertion end 10, which is rounded in shape, and a straight proximal end 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 on this [Fig.1], is fitted with notches 15 aligned transversely with respect to the axis of introduction, and intended for the creation of an anchorage in the bone material.

[0030] The screw 2 consists of a compression screw, which for this purpose has a non-constant thread pitch, that is to say it comprises a threaded distal part 20 and a threaded proximal part 21, separated by a smooth section 22, while the thread pitch of the proximal part 21 is smaller than the thread pitch 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 should 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 part 20 and proximal part 21 are preferably provided with tapping notches, respectively 23 and 24. On the other hand, the proximal part 21 has a diameter greater than that of the distal part 20, so that its thread cuts in the bone material a different tapping than that cut upstream by the thread of the distal part 20.

[0033] With reference now to Figures 2 and 3, the system according to the invention can be seen being installed at one of the two facet joints of two vertebrae, and more particularly, viewed posteriorly, the joint between the left process 3 of one vertebra and the left process 4 of the adjacent vertebra positioned below. The right side is treated in the same way.

[0034] In previous steps not shown, the two apophyses 3 and 4 are prepared, namely that the joint capsule and the osteophytes have been removed, then the facet joint line is opened to create a cavity 5 at the level of the interface space which is further reshaped 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 snugly into it.

[0036] It should be noted that from an operative technical point of view, the introduction of the 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 should 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 placement 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 and then in the upper apophysis 3, passing through the opening 12 of the implant 1, possibly with a aiming device.

[0039] The screw 2 is then screwed into this hole, which makes it possible on the one hand to prevent 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, to allow the apophyses 3 and 4 to be tightened on the implant 1 and more particularly the notches 15 of the latter, and thus ensure perfect maintenance and promote bone fusion.

[0040] In Figures 2 and 3, the screw 2 is perfectly perpendicular to the principal plane of the implant 1; however, this is a special case since the insertion axis of the screw 2 may very well form an angle with this plane. As the drilling is carried out blindly after the insertion of the implant 1, the opening 12 preferentially, but not exclusively, has large dimensions compared to the transverse dimensions of the screw 2, so as to allow considerable leeway when a aiming device is not used.

[0041] It should also be noted that, insofar as a high-performance sighting device can be used, it may be envisaged that the opening 12 could 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 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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