EP4225221A1 - Disc prosthesis device for the cervical spine - Google Patents

Abstract

Disc prosthesis comprising an insert in the form of a flexible cushion, a first half-shell (10a) and a second half-shell (30a), the insert in the form of a flexible cushion being positioned between the half-shells, characterised in that a first of the half-shells (10a) comprises a first base provided with a first surface (12a) for hooking on to a first vertebra and a recessed annulus (15a) for forming a first cup (11a) and in that a second (30b) of the half-shells is provided with a first surface for hooking on to a second vertebra and a second surface bearing a rim (33a) surrounding a second cup (31a), the cups (11a, 31a) facing each other each receiving an upper crown (21) and a lower crown (23) of the insert, the annulus and the rim forming walls that slot together with play and making stops for angular and shearing movements between the half-shells.

Description

Description

Title: CERVICAL RACHIS DISC PROSTHESIS DEVICE

Technical area

The invention relates to the field of implantable vertebral disc prostheses and in particular vertebral disc prostheses in particular adapted to the cervical spine.

Prior technique

[0002] The wear of the vertebral discs leads to the need to make disc prostheses.

Disc prosthesis devices such as an intervertebral disc prosthesis are known in the form of an inseparable structure which comprises a rigid upper plate, a rigid lower plate and an intermediate cushion, elastically compressible and housed between the internal surfaces of the two plates, the cushion having, in the free state that is to say without compressive stress, the shape of a wedge between the two plates. Also known is a disc prosthesis device comprising a flexible ring between two flat plates, the space in the center of the ring being filled with a gel or a liquid or an intervertebral prosthesis comprising a disc-shaped bladder filled with a gel and surrounded by a flexible ring.

Technical problem

[0004] These devices offer few limits to the inclination movements of the vertebrae with respect to an axis connecting the vertebrae perpendicular to the cushion, to the rotational movements around this axis or to the shear movements according to the plane of the cushion. It is necessary to improve disc prostheses by limiting the freedom of movement of the vertebrae to which the prosthesis is attached. Such a prosthetic device must also be easy to manufacture, even in small dimensions making it usable as a cervical disc prosthesis, and be easy to implant. It is additionally desirable to be able to control the height of the prosthesis for its preparation and its implantation.

Disclosure of Invention

To do this, the present application proposes a disc prosthesis comprising an insert in the form of a flexible cushion, a first half-shell, a second half-shell, the insert in the form of a flexible cushion being positioned between said half- shells, for which a first of the half-shells comprises a first base provided with a first face for attachment to a first vertebra and with a second face carrying a crown surrounding a first cup and for which a second of the half- shells is provided with a first face for attaching to a second vertebra and with a second face bearing a border surrounding a second cup, said face-to-face cups receiving respectively an upper cap and a lower cap of said insert, said crown and said border forming facing inclined walls fitting together with a clearance (g) and producing stops for angular movements (a) and for shearing movement (C1, C2) between the half-cocks ills said facing inclined walls forming abutments both in approximation and in inclination of a half-shell relative to the other half-shell, said half-shells being kept apart by the insert during normal physiological stresses on the prosthesis.

The prosthesis of the invention, particularly well suited to making a cervical disc prosthesis is easily implantable, can be made in small sizes compatible with implantation at the level of the cervical vertebrae, allows limited movements between these vertebrae.

[0007] The characteristics described in the following paragraphs can optionally be implemented. They can be implemented independently of each other or in combination with each other.

[0008] Advantageously, said crown and said border comprise facing walls inclined at complementary inclinations. [0009] A foot of said border may be surrounded by a collar extending from the first face of the second half-shell.

[0010] Said crown and said border may have a circular, oval or rectangular base with rounded corners.

Said crown and said border having a rectangular base with rounded corners, said corners advantageously form stops in rotation of one of the half-shells with respect to the other around an axis substantially perpendicular to the planes of the faces of attachment of the half-shells.

The insert in position between the half-shells, the latter can be movable relative to each other in inclination relative to an axis initially perpendicular to the first base and to the second base by crushing or deformation of at least part of one edge of the insert.

[0013] The insert in the form of a flexible cushion can be an insert of generally spheroidal shape with flattened or non-flattened polar caps.

[0014] The insert in the form of a flexible cushion can be hollow.

The hollow insert is advantageously filled with a gas, a liquid or a gel.

[0016] Preferably, the hollow insert is filled with an incompressible deformable material. The insert can also be solid and itself deformable and incompressible.

[0017] At least one of the bases can comprise a mesh structure and/or indentations, grooves, ridges or comprises a porous texture for hooking (112) to the bone of the vertebra against which it is applied.

[0018] Said insert and said half-shells can be glued together or nested by means of forms of complementary geometries.

Brief description of the drawings

Other characteristics, details and advantages of the invention will appear on reading the detailed description below, and on analyzing the appended drawings, in which: [0020] [Fig. 1] shows an exploded view of a prosthesis according to a first embodiment;

[0021] [Fig. 2] shows a cutaway perspective view of an example insert;

[0022] [Fig. 3] shows a longitudinal sectional view of an example of half-shell production;

[0023] [Fig. 4] shows a cutaway perspective view of a second embodiment of a prosthesis;

[0024] [Fig. 5] shows a schematic view of the degrees of freedom of a prosthesis of the invention;

[0025] [Fig. 6A] shows a schematic cross-sectional side view of an undeformed demand prosthesis;

[0026] [Fig. 6B] shows a schematic cross-sectional side view of the prosthesis of FIG. 6A angularly deformed.

Description of embodiments

The drawings and the description of non-limiting examples of the invention can not only serve to better understand the present invention, but also contribute to its definition, if necessary.

Reference is now made to Figure 1 which shows an implant or disc prosthesis of the application in exploded view according to a first embodiment. Said implant is a system which comprises a first half-shell 10a called the upper half-shell, an intersomatic element in the form of a flexible insert 20 and a second half-shell 30a called the lower half-shell.

[0029] The external faces of the half-shells constitute plates in contact with the vertebrae between which the implant is placed.

[0030] The flexible insert is received in facing cups 11a, 31a formed in the half-shells.

[0031] The implant is more particularly suitable for producing a cervical disc prosthesis. The flexible insert is advantageously a cushion as shown in Figure 2. This insert can be spheroidal in shape and have its pole caps 21, 32, caps in contact with the inside of the half-shells, flattened or not. The flexible insert can advantageously be hollow and comprise a flexible equatorial rim.

[0033] The hollow insert is sealed and contains a gas, a liquid or a gel depending on the flexibility that one wishes to give it.

A particular embodiment, the hollow flexible insert is filled with a liquid or an incompressible gel 40, therefore its deformations will be by deformation of the strapping 22 as shown in Figures 6A, 6B for example.

[0035] According to Figure 3, for the embodiment of Figure 1, the upper and lower half-shells comprise inclined walls 13, 14 forming stops both in approximation and in inclination of a half-shell relative to the other half-shell.

According to Figure 4 which shows a second embodiment of half-shells of the invention, the upper half-shell 11b and the lower half-shell include abutment means formed by a lower edge 15 of the half -upper shell and a flange 16 of the lower half-shell.

[0037] The interest of a flexible insert arranged between two half-shells is to approximate the anatomy of a vertebral disc:

- No fixed center of mobility in the form of a ball joint type mechanical connection or other;

- The kinematics of the implant is essentially ensured by the flexible insert 20 called intersomatic insert.

- The half-shells, once positioned between the vertebrae, enclose the flexible insert and are able to rotate around the flexible insert while forming stops.

[0038] The implant has damping properties thanks to the flexible insert 20 which, as arranged between the half-shells, allows dynamic stabilization not rigid. By making this hollow flexible insert with walls of variable thickness, the implant can be provided with variable rigidity making it possible to adapt the stiffness of the insert according to different axes of rotation.

In this case, the flexibility of the flexible insert must be able to allow the natural movements of the head relative to the bust and thus generate inclinations of amplitude greater than 14° in flexion-extension and anteroposterior translation ( shear) at least 0.6mm to 2mm depending on the size of the implant for cervical application. These are therefore significant deformation amplitudes of approximately 10 to 15%.

[0040] Therefore, the concept of play between the half-shells is essential in the invention, the play being such that in normal operation, that is to say in the ranges of angulations and physiological translations, the upper half-shell does not come into contact with the lower half-shell, the cushion ensuring its balance.

[0041] Furthermore, the shape of the half-shells is defined to allow easy and intuitive centering of the implant with respect to the plates of the treated level.

[0042] The crown 13a, 13b of the first half-shell, and the edge 33a, 33b of the second half-shell which fit into each other with play form a container for the flexible insert. The inner wall of the border as well as the cup 11a form retaining walls of this implant.

[0043] The anchoring of the implant at the level of the vertebral plates is ensured by a structure favoring attachment to the vertebrae, for example a mesh structure supplemented or not with ribs 12 and/or studs to present good characteristics. of osseointegration. It is also possible to give the surface in contact with the bones a porous texture, for example by chemical treatment or the addition of a layer of porous material. A Hydroxide Apatite coating can also be made on the faces of the half-shells in contact with the vertebrae.

[0044] The half-shells can be produced from a 3D print modeled on the patient's anatomy. The material constituting them can be based of titanium alloy, a material of the urethane type, PEEK (polyether-ether-ketone), a ceramic or any other biocompatible material that is sufficiently resistant and adapted not to release particles during friction between the half-shells. The half-shells can also be made with combinations of said materials, for example to make an outer gripping layer and an inner layer that is not very sensitive to friction.

The range of implants is available in three or four sizes adapted to the morphologies of the vertebrae of the patients.

[0046] The materials of the implant are chosen to offer significant radio-transparency and offer very good compatibility with MRI imaging.

The shape and dimensions of the implant make it possible to use an ancillary of reduced dimensions.

Both in the embodiment of Figure 1 and in that of Figure 3, one of the half-shells 10a, 10b is partially positioned in the other half-shell 30a, 30b with a longitudinal play, laterally and in rotation around the flexible insert.

In a direction of crushing of the flexible insert, according to Figure 3, the cup of the lower half-shell is surrounded by a border in the form of an inclined outer wall 33a on which can come support an inclined inner wall 13a, an edge of the upper cup. This constitutes a crushing stop which makes it possible to control the height of the prosthesis for its preparation and its implantation. Similarly, once implanted, an inclination of one of the half-shells relative to the axis will be limited by the contact between the inclined walls.

In the case of Figure 4, the abutment during the crushing of the insert takes place between the top 15 of the wall 10b and the collar 16 while the abutment in inclination of the half-shells relative to each other will be on the inclined walls 13b, 33b.

Figure 5 shows the various possible movements of the half-shells 10, 30 of the embodiment of Figure 1 relative to each other. According to this figure, the walls 13, 14 are originally separated by a clearance g obtained by the fact that the upper half-shell resting on the insert, the sloping walls 13, 14 of the crown and the rim are separated from each other by the insert. Firstly, an inclination of one of the half-shells at an angle a with respect to the vertebral axis A is possible but limited by the abutment on one side or the other of the walls 13, 14.

The shearing movement C1, C2 is also limited by the play g between the walls 13, 14. The rotational movement p of one of the shells relative to the other around the axis A is itself limited by the generally rectangular shape of the half-shells as seen in FIG. In the case of the embodiment of FIG. 4 and of a compression movement in the direction H, the free top of the crown 15 comes into abutment on the collar 16. Similarly, in the case of the embodiment of 3, the wall 33b or its top may come into abutment with the internal wall 13b of the bowl of the lower half-shell 10. These contactings only occur, however, in the event of abnormal compression or failure of the the insert as security.

[0053] Figures 6A and 6B show the deformation of the cushion 20 between the half-shells during an inclination of one of the half-shells relative to the other, still in the case of the example of Figure 3 .

In the case of the embodiments of Figures 3 and 4, a shear movement of one of the half-shells relative to the other will be limited by the contacting of the walls 13a, 13b, 33a, 33b .

[0055] The half-shells and the vertices of the flexible insert can be glued together to form a one-piece disc, which is easier to implant.

For a vertebral implant of the cervical disc prosthesis type, three to four sizes of implants can be provided and the dimensions of this implant can be of the order of:

- Small size: width on the order of 12 to 14 mm, length on the order of 14 to 16 mm;

- Average size width of the order of 14 to 16 mm, length of the order of 16 to 18 mm; - Large size width of the order of 16 to 18 mm, length of the order of 18 to 20 mm.

The heights of the implants can be of four sizes in the order of 4 to 5 mm, 5 to 6 mm, 6 to 7 mm or 7 to 8 mm depending on the morphology of the patients who will receive it.

[0057] The half-shells can be two-component, with:

- a contact part with the vertebrae in titanium alloy for good integration in the vertebral endplates. A certain porosity (not shown) can also be used for recolonization, produced by additive manufacturing;

- a part in contact with the cushion and in contact with each other in movement in polymer such as PEEK, PEKK, polyethylene to offer low abrasion.

[0058] It is also possible to envisage mono-component half-shells, in this case we would opt for a ceramic or even titanium alloy but with a coating making it possible to harden and improve the wear properties of the central parts, or finally all polymer with the surfaces of the trays in contact with the bone coated with materials conducive to osteogenesis.

The cushion can be made of silicone, polyurethane, or deformable polymer and, once positioned in the half-shells, must allow in combination with the latter a flexion-extension mobility of the order of 18° combined with a translation variable antero-posterior according to the sizes, in particular an amplitude of approximately 1 mm to 2 mm, a lateral inclination of the order of 15° and a rotation of at least 10° according to the play g obtained when the half-shells are positioned on the cushion and thus separated from each other during normal physiological stresses.

The invention is not limited to the examples described above, only by way of example, but it encompasses all the variants that a person skilled in the art may consider in the context of the protection sought. In particular, the terminology upper half-shell and lower half-shell is only used for convenience to help with reading, it being understood that the insert can also be positioned upside down.

Claims

Claims [Claim 1] Disc prosthesis comprising an insert in the form of a flexible cushion, a first half-shell (10a, 10b), a second half-shell (30a, 30b), the insert in the form of a flexible cushion being positioned between said half-shells, characterized in that a first of the half-shells (10a, 10b) comprises a first base provided with a first face (12a, 12b) for attachment to a first vertebra and with a second face bearing a ring (15) surrounding a first cup (11a, 11b) and for which a second (30a, 30b) of the half-shells is provided with a first face (32a, 32b) for attachment to a second vertebra and a second face bearing an edge (33a, 33b) surrounding a second cup (31 a, 31 b) said cups (1 1 a, 31 a, 1 1 b, 31 b) facing each other respectively receiving an upper cap (21) and a lower cap (23) of said insert, said crown and said border forming facing inclined walls fitting together with a play (g) and producing stops for angular movements (a) and for shear movement (C1, C2) between the half-shells, said facing inclined walls forming stops both in approach and in inclination of a half- shell with respect to the other half-shell, said half-shells being held apart by the insert during normal physiological stresses on the prosthesis. [Claim 2] Disc prosthesis according to claim 1, for which said crown and said border comprise facing walls inclined at complementary inclinations. [Claim 3] Disc prosthesis according to claim 1 or 2, for which a foot of said edge (33b) is surrounded by a collar (16) extending from the first face (32b) of the second half-shell. [Claim 4] Disc prosthesis according to claim 1, 2 or 3, wherein said crown (15) and said border (33a, 33b) have a circular, oval or rectangular base with rounded corners. [Claim 5] A disc prosthesis according to claim 4, wherein said crown (15) and said border (33a, 33b) have a rectangular base with rounded corners said corners forming stops in rotation (0) of one of the half-shells with respect to the other around an axis (A) substantially perpendicular to the planes of the attachment faces of the half-shells. [Claim 6] Disc prosthesis according to any one of the preceding claims, for which, the insert (20) in position between the half-shells (10a, 30a, 10b, 30b), the latter are movable relatively to one relative to the other in inclination (a) relative to an axis (A) initially perpendicular to the first base (12a, 12b) and to the second base (32a, 32b) by crushing or deformation of at least part from one edge of the insert. [Claim 7] Disc prosthesis according to any one of the preceding claims, for which the insert in the form of a flexible cushion is an insert of generally spheroidal shape with polar caps (21, 23), flattened or not. [Claim 8] Disc prosthesis according to any one of the preceding claims, in which the insert (20) in the form of a flexible cushion is hollow. [Claim 9] A disc prosthesis according to claim 8 wherein the hollow insert (20) is filled with a gas, liquid or gel. [Claim 10] A disc prosthesis according to claim 8, wherein the hollow insert (20) is filled with an incompressible deformable material. [Claim 11] Disc prosthesis according to any one of the preceding claims, in which at least one of the bases comprises a mesh structure and/or indentations, grooves, ridges or comprises a porous gripping texture (112) on the bone of the vertebra against which it is applied. [Claim 12] A disc prosthesis according to any preceding claim, wherein said insert (20) and said half-shells (10, 30) are glued together or interlocked by means of shapes of complementary geometries.