EP2142148A2

EP2142148A2 - Expanding cage for spinal surgery

Info

Publication number: EP2142148A2
Application number: EP08787841A
Authority: EP
Inventors: David Attia; Francisco Ros Guillen
Original assignee: Individual
Current assignee: Individual
Priority date: 2007-03-28
Filing date: 2008-03-25
Publication date: 2010-01-13
Also published as: FR2914180A1; FR2914180B1; WO2008135669A3; WO2008135669A2; US20100234956A1; US8491657B2

Abstract

The invention relates to an expanding device (1) intended to be implanted between the vertebral end-plates of two adjacent vertebrae, in particular for a stabilisation operation for intervertebral fusion. The inventive device comprises: a cage forming a peripheral part that surrounds a central cavity, said peripheral part being formed by a leading edge (3) and a thicker manipulation edge (2) which are connected by two lateral edges (4) provided with lateral housings (5); and a retractor (7) received in the lateral housings (5), which can be moved between an insertion position, in which it is located close to the manipulation edge, and a locking position, in which it is located at the leading edge, increasing the height of same. The invention is characterised in that the retractor (7) is provided with abutment means designed to maintain the retractor (7) in the locking position and to oppose the release of the retractor from the cage.

Description

EXPANDED CAGE FOR VERTEBRAL SURGERY

TECHNICAL FIELD OF THE INVENTION

The present invention relates to an implant used in vertebral surgery and in particular for the treatment of diseases of the cervical or lumbar intervertebral disk.

STATE OF THE ART

[002] Such an implant is intended to be inserted between two cervical or lumbar vertebrae. Its function is to restore or maintain the space corresponding to the vertebral disk treated and the anatomical situation of the latter, in particular to restore the vertebral column a natural curvature and to reopen the holes of conjugation which are of share and of other of the disc. Once the implant is installed, a final fusion of the two vertebrae is achieved by growing the bone cells through the implant which is provided for this purpose with an internal cavity receiving bone graft, natural or synthetic, open to each from its ends to allow contact of the graft with the respective vertebral trays. The whole operation is known as a stabilization operation for intervertebral fusion.

[003] An implant for a stabilization operation for intervertebral fusion can be inserted anteriorly, that is to say that it is introduced through the anterior part of the intervertebral space, or posteriorly through the canal. vertebral. Posterior introduction poses a number of problems, including the need to distance nerve structures. The introduction by anterior route, it is complicated by the fact that the intervertebral space is particularly narrow. Access can be facilitated by means of surgical retractor instruments, but progression to the posterior part of the space is difficult. The implant is usually put in place by impacts exerted on its end by means of a hammer. He then tends to sinking in the posterior part of the vertebral plates without opening the conjugation holes and thus without allowing decompression of the nerve roots concerned.

[004] In addition, under the effect of vertebrae movements, existing implants tend to migrate and in some cases be expelled.

[005] The known implants for anterior insertion are generally of quadrangular shape.

[006] The patent application WO98 / 10722 describes an expansive implant comprising branches connected at one of their ends by a base pierced with a port that can be slid by the posterior route between the vertebral trays of two consecutive vertebrae in order to maintain at a given distance and restore the stability of the spine. The branches and the base delimit a hollow cage which, in the rest position, has a cylindrical outer profile and conical inner profile. A wedge is adapted to be introduced into said cage, the displacement of said wedge inside said cage being adapted, because of the conical inner profile of the latter, to mutually separate said branches.

[007] The prior art also knows the patent EP1415622 which describes an expansive implant that can be slipped by the posterior route between the two trays of two vertebrae, and in particular between two lumbar vertebrae. Between two successive vertebrae, two implants such as those described in patent EP1415622 are placed side by side.

[008] The implants described in these two patents have a number of disadvantages. Primarily, they do not fill the vertebral space and offer a limited graft surface. Moreover, they are rather intended to be introduced via the posterior canal through the vertebral canal, which implies a prior separation of nerve structures. OBJECT OF THE INVENTION

[009] One of the objects of the present invention is to provide an implant insertable anteriorly between the vertebral endplates of two adjacent vertebrae and be stably housed between these trays while providing a large graft surface.

For this purpose, the invention relates to an expansive device intended to be implanted between the vertebral endplates of two adjacent vertebrae, in particular for a stabilization operation for intervertebral fusion, comprising:

a cage constituting a peripheral part surrounding a cavity. central, the peripheral portion consisting of a leading edge and a thicker handling edge, connected by two lateral edges provided with lateral housings; and

- spacer means received in the lateral housing, the spacer means being movable between an insertion position, in which it is close to the manipulation edge, and a locking position, in which it is at the edge of the attack whose thickness he increases,

the spacer means being provided with stop means adapted to maintain the spacer means in its locking position and to oppose the expulsion of the spacer means of the cage.

By "leading edge" is meant the edge which is intended to be inserted between the vertebral plates, while "manipulation edge" means the opposite edge, on which are generally exerted the forces (thrust or impacts) intended to penetrate the device between said vertebral plates. The term "side edges" refers to the branches that connect the handling edge to the leading edge. In the following, the term "longitudinal" means a direction parallel to the leading edge and the term "lateral" means a direction parallel to the side edges. Once implanted, the expansive device is disposed between two vertebral trays so that the plane formed by the lateral edges, of attack and handling is parallel to the two vertebral plates between which it is placed. Moreover, the term "height" designates a dimension perpendicular to the plane formed by the lateral edges, of attack and manipulation.

The implant according to the invention may therefore have a generally quadrangular plan shape as in the prior art but its section has a wedge shape of variable angle, that is to say a trapezoidal shape of which the small base is of variable size.

Furthermore, the spacer means is provided with stop means for maintaining the spacer means in its locking position, and in particular to prevent the spacer means from leaving the cage at the end of expansion.

In particular, the abutment means oppose the lateral expulsion of the spacer means.

In addition, in a particular embodiment of the present invention, the stop means oppose the expulsion of the spacer means by the leading edge.

Advantageously, the leading edge comprises a housing for receiving the spacer means so as to cause the thickness increase of the leading edge in the locking position.

According to a preferred embodiment, the lateral housings are slots arranged along the lateral edges and the spacer means is a rod whose ends are adapted to be inserted into the slots forming the lateral housings, the dimensions of the ends of the the rod being greater than the height of the slots, so that the rod causes an increase, by elastic deformation, the height of the device at the level where the rod.

Furthermore, the leading edge preferably comprises a slot extending the slots forming the lateral housing, said slot being adapted to receive the spacer means so as to cause the expansion of the leading edge.

In addition, the housing of the leading edge is advantageously constituted by a zone of greater height of the slot of the leading edge.

Advantageously, the slots forming the lateral housing have a decreasing height between the handling edge and the leading edge.

The slot of the leading edge interconnecting the slots forming the lateral housing allows a progressive separation of the assembly formed by the side edges and the leading edge in two tongues, each of the tabs being parallel to the formed plane. by the side edges, the leading edge and the manipulating edge, and each of the tabs projecting from the handling edge. During the progression of the spacer means from its insertion position to its locking position, the height of the lateral housing is increased gradually and the tabs are spaced from one another.

Advantageously, the abutment means are lateral and located at the ends of the rod engaged with the slots forming the lateral housing, the ends of the rod being provided with lateral stops of greater diameter forming lateral locking means.

This ensures in particular that the rod remains parallel to the leading edge during its progression through the device.

In addition, the spacer means preferably comprises two parts, the part which is on the side of the manipulation edge being higher than the part which is on the leading edge side, so that the part which is on the side of the edge of manipulating abuts against the leading edge, thus opposing the expulsion of the spacer means by the leading edge.

Advantageously, the portion of the spacer means which is on the side of the handling edge is between the side edges. This part may also have a length substantially equal to that of the central cavity, which allows it to play further a guiding role allowing the spacer means to progress parallel to the leading edge when it passes from its position. insertion to its blocking position.

In addition, the spacer means comprises a portion between the side edges and having a T-shaped section, the foot of the T cooperating with the walls of the slot of the leading edge, and the bar of the T coming in abutment against the leading edge.

Preferably, the part of the spacer means which is on the leading edge side has a length equal to that of the leading edge, so that the part which is on the leading edge side supports the edge of the leading edge. attack throughout its length when the spacer means is in the locking position.

Advantageously, the leading edge and the handling edge are longer than the lateral edges.

Thus, the implant has a shape close to the intervertebral disk that it replaces.

According to a preferred embodiment, said lateral edges are curved.

In particular, the lateral edges are shaped so that the posterior lordosis of the device is substantially equal to 4 ° when the spacer means is in the locking position.

Advantageously, the lateral edges extend substantially rectilinearly from the handling edge and then curve towards the edge. attack.

According to one embodiment of the present invention, the leading edge and the lateral edges constitute two upper and lower U-shaped tongues connected to the manipulation edge and facing each other delimiting between them the slot of the leading edge. and the side housings.

Advantageously, the upper tongue has a convex upper interface wall with an upper vertebral plateau, the lower tongue having a concave lower wall interface with a lower vertebral plateau.

[0036] Advantageously, the cage is made of a single piece.

Advantageously, the cage is made of PolyetherTherketone (PEEK).

In addition, the spacer means is preferably a one-piece piece.

The invention also relates to a surgical method of introduction, by anterior route, an expansive device according to any one of the preceding claims to replace a damaged vertebral disc between two cervical vertebrae, comprising the following steps :

- Difference of the two cervical vertebrae,

- Removal of the damaged vertebral disc,

- Inserting the expansive device by its leading edge (3) between the two vertebrae, the expander means (7) of the expansive device being in its insertion position, so that the expansive device occupies the entire area initially occupied by the operated intervertebral disc, - Placing the spacer means (7) in its locking position.

BRIEF DESCRIPTION OF THE FIGURES

The present invention will be better understood on reading the description of a nonlimiting example which follows, with reference to the accompanying drawings in which:

FIG. 1 is a schematic perspective view of an expansive device in the insertion position according to an embodiment of the present invention in which the abutment means of the rod are lateral,

FIG. 2 is a view similar to that of FIG. 1 in the locked position,

FIG. 3 is a side plan view of the device of FIG. 1,

FIG. 4 is a side plan view of the device of FIG. 2,

FIG. 5 is a sectional view in the direction AA of the device of FIG. 3,

FIG. 6 is a sectional view in the direction AA of the device of FIG. 4,

FIG. 7 is a schematic perspective view of an expansive device, in the locked position, according to another embodiment of the present invention in which the abutment means are located along the entire length of the rod,

FIG. 8 is a cross-sectional view of the device of FIG. 7, FIG. 9 is a perspective view of a section of the device of FIG. 7,

FIG. 10 is a side view of the device of FIG. 7 in the locked position,

FIG. 11 is a side view of the device of FIG. 7 in insertion position,

FIG. 12 is a front view of the spacer means according to the embodiment of FIG. 7,

FIG. 13 is a side view of the spacer means according to the embodiment of FIG. 7,

FIG. 14 is a view from above of the device of FIG. 7,

FIG. 15 is a perspective view of the device of FIG. 7 in the locked position,

- Figure 16 is a perspective view of the device of Figure 7 in the insertion position.

EXAMPLE OF REALIZATION

Referring to Figures 1 to 6, an expansive device 1 is intended to be implanted between the vertebral plates of two adjacent vertebrae, in particular for stabilization intervertebral fusion. This device is in accordance with an embodiment of the present invention in which the abutment means are lateral.

Overall, the device 1 is a cage-shaped implant with an empty central space 16 delimited by a peripheral frame comprising an edge of 2, a leading edge 3 and two side edges 4 provided with lateral housings 5 adapted to receive a spacer means 7 movable between an insertion position, shown in Figures 1, 3 and 5, in which there is located near the handling edge, and a locking position, shown in Figures 2, 4 and 6, wherein it is at the leading edge whose height is then increased to ensure the locking of the implant between trays.

The implant 1 is made of biocompatible elastic material suitable for expansion. Advantageously, this material has a modulus of elasticity close to the bone. Advantageously, this material is also radiolucent. Advantageously, the implant is made of PEEK. Alternatively, it may also be metal such as titanium, or resorbable material such as PLLA.

Figures 1, 3 and 5 show the implant 1 in the insertion position.

The implant 1 comprises a leading edge 3 and a handling edge 2 of greater thickness than the leading edge. The handling edge comprises in its central part a through recess 6 allowing in particular the control of the spacer means. The leading edge and the handling edge extend parallel and have the same length. However, the leading edge is slightly offset in the direction of the height relative to the handling edge, so that the lateral edges are curved so as to have a 4 ° lordosis at the end of expansion of the implant 1 to allow the implant to marry the shape of the vertebral endplates, which allows the spine to return to its natural curvature. The curvature of the lateral edges is more marked at the leading edge. Overall, these lateral edges extend substantially rectilinearly from the handling edge and then curve toward said leading edge.

Furthermore, the leading edge and the handling edge are longer than the side edges to reproduce the shape of the vertebrae at best. The four edges therefore form a rectangle longer than wide.

The implant 1 has - in the insertion position - a general trapezoidal wedge shape whose end is slightly bent. This shape is chosen to be adapted to the easiest possible insertion between the vertebral trays.

The lateral housings are slots 5 formed along the side edges. These slots traverse the side edges from one side to the other and have a decreasing height from top to bottom. They start from a position of greater height in the vicinity of the leading edge 2 and extend to the bottom of the implant where they are extended at the leading edge by a slit 9 which passes through the leading edge from side to side. In this way, the assembly formed by the side edges and the leading edge is divided by these slots into two independent tongues 4A and 4B can be spaced apart from each other. The wall of the tongue 4A is convex while the lower wall of the tongue 4B is concave.

A housing 8 provided to accommodate the expansion means in the locking position is constituted by a cylindrical area of diameter greater than the thickness of the slot 9 formed at a portion of the latter being slightly above from the median plane of the leading edge.

The spacer means 7 is -asi better seen in Figure 6- consists of a cylindrical rod whose ends 10 have a diameter smaller than that of the central portion and end with stops of greater diameter 11 forming lateral locking means.

As can be seen in the figures, the central diameter of the rod 7 is much greater than the height of the slot 9. The diameter of the ends 10 of this rod is much greater than the height of the slots 5 to level of the lower part of the implant and substantially equal to the height of these slots 5 at the upper end of these slots 5. When said rod is in the introduction position shown in Figures 1, 3 and 5, it has substantially no action on the side edges 4 and the implant has substantially the shape it would without this rod. The progression of the rod will cause the progressive spacing of the tongues 4A and 4B, that is to say an increase in the height of the implant at the area where the rod is located, by elastic deformation. This increase in height is maximum when the rod is in the locking position in the housing 8. Optionally, the diameter of the ends 10 may be slightly greater than the height of the upper end of the slots 5 in order to increase slightly the height of the upper part of the lateral edges 4 in the insertion position of the implant. The choice of the material of the implant ensures that the deformation of the implant remains elastic deformation regardless of the amplitude of this deformation.

In blocking position, as can be seen in particular in Figure 4, the height of the leading edge 3 is substantially equal to the height of the handling edge, which ensures immobilization of the implant between the two trays. If necessary, it is possible to provide a rod diameter such that the height of the leading edge remains slightly less than the height of the handling edge.

Advantageously, the implant 1 comprises on its faces intended to come into contact with the vertebral plates of the teeth 12 for improving the grip of the implant and its anchoring.

The usual surgical technique requires the use of an intervertebral retractor screwed temporarily on the vertebral bodies in order to destroy the space to be able to remove the disc in full and insert the implant. The implant is inserted by its leading edge, a thrust being exerted on the handling edge. Alternatively the insertion can be carried out by hammer impacts applied to the handling edge. In the insertion position, the rod 7 is in abutment against the upper ends of the slots 5. The wedge shape that the implant then facilitates its insertion. Once the implant is installed, the rod 7 is moved by sliding in the slots 5 and 9 until arriving in the housing 8. The manipulation of the rod can be done advantageously by means of a tool inserted through The recess 6. Advantageously, a guiding device (not shown) is installed in the installation area of the implant. It may be for example cylindrical slides disposed on either side of the implant and cooperating with spherical shapes disposed on either side of the rod (instead of stops 11). It may also be two parallel and integral rods introduced on either side of the recess 6.

The progression of the rod will move the two tongues 4A and 4B away from each other, so that the profile of the implant will progressively change from the shape shown in Figure 3 to the shape shown in FIG. Figure 4 wherein the height of the implant is substantially the same throughout its length. At the end of the stroke, the rod is wedged inside the leading edge 3, which then forms a rigid reinforcement rendering said edge resistant to compression.

This expansion of the implant makes it possible to anchor it in the vertebral endplates, to discard the posterior part of the intervertebral space and thus to widen the height conjugation channels and to give space to the nerves. corresponding tablets. It releases an interior space able to receive an autologous or artificial bone graft.

FIGS. 7 to 17 show an implant according to another embodiment of the present invention in which the spacer means has an abutment means having a T-shaped profile in FIG. 8, said stop means opposing the expulsion of the spacer means by the leading edge. The same numbering is repeated for the elements common to the previous embodiment and reference will be made usefully to the description of the first embodiment for certain details. In particular, the side edges, etching and handling are the same as in the previous embodiment. In this embodiment, only the spacer means, which differs from that of the mode of previous realization, will be described in detail.

Thus the spacer means 7 of Figures 7 to 17 comprises a portion between the side edges 4 and having a T-shaped section. The spacer means is a rod having two generally parallelepipedal portions 14 and 15, such as the height. of Part 14 is greater than the height of the part

15.. Indeed, the portion 14 has a height h1 and the portion 15 has a height h2 such that h1 is greater than h2. Furthermore, the portion 15 of the spacer means 7 has a length L1 equal to the length L3 of the leading edge 3. The portion 14 of the spacer means 7 has a length L2 slightly smaller than the length L4 of the central cavity of the implant 1.

Initially, the spacer means 7 is in a visible insertion position in Figures 11 and 16, in which it is close to the manipulation edge 2. The portion 14 is in the central cavity 16 so that it does not exert any action on the lateral edges whatever the position of the spacer means 7. Moreover, the height h2 is such that in this insertion position, the spacer means 7 does not exert any action on the lateral edges 4 and the implant 1 has the shape that it would have without this spacer means 7.

When the spacer means 7 is pushed to approach the leading edge 3, the portion 14 of the spacer means 7 moves in the central cavity 16 of the implant 1 so that the spacer means 7 does not exert On the other hand, the part 15 of the spacer means 7 progressively spreads the tabs 4A and 4B by elastic deformation and then increases the height of the lateral housings 5.

This increase in height continues until the portion 15 of the spacer means 7 reaches the leading edge 3 at which the spacer means 7 is stopped via the part 14. Indeed the part 15 has a width 11 substantially equal to the width 12 of the leading edge and the inner wall 16a of the central cavity 16, so that when the portion 15 of the spacer means 7 reaches the leading edge 3, the portion 14 of the spacer means 7 reaches the inner wall 16a. The portion 14 thus abuts against the wall 16a of the central cavity 16, which blocks the progression of the spacer means 7. Part 14 of the spacer means 7 thus opposes the expulsion of the spacer means 7 by the leading edge.

Furthermore, each of the inner walls of the lateral edges is provided with a stop step 13a or 13b, located at a distance 13 from the outside of the leading edge greater than or equal to the width 11 of the portion 15. of the spacer means 7. These stops oppose a return of the spacer means to its insertion position.

In addition the side walls 14b and 14c of the portion 14 of the spacer means 7 are parallel to each other and to the side walls 16b and 16c of the central cavity. These walls form stops opposing the lateral expulsion of the spacer means 7. The side walls 14b and 14c are further spaced a distance slightly less than the distance between the walls 16b and 16c of the central cavity, if although the walls 14b and 14c of the portion 14 guide the spacer means 7 during its passage between its insertion position and its locking position.

Furthermore, the portion 15 has a length L1 equal to the length L3 of the leading edge, which makes it possible to reinforce the mechanical strength of the implant 1 since the part 15 of the spacer means 7 supports the edge. attack on its entire length.

Of course, many variants are possible. Thus the spacer means may take various forms, and it may for example combine means of lateral and longitudinal stops. In addition, the implant may be made of any elastic biocompatible material, of one or more tenants. Furthermore, the implant can be made of a plastically deformable material when it is likely to be removed later.

Claims

An expansive device (1) intended to be implanted between the vertebral endplates of two adjacent vertebrae, in particular for a stabilization operation for intervertebral fusion, comprising:

a cage constituting a peripheral part surrounding a central cavity, the peripheral part consisting of a leading edge (3) and a thicker manipulation edge (2) connected by two lateral edges (4) provided with side housings (5); and

- a spacer means (7) received in the lateral housings (5), the spacer means (7) being movable between an insertion position, in which it is close to the manipulation edge, and a locking position, in which it is at the level of the leading edge of which it increases the height,

characterized in that the spacer means (7) is provided with stop means adapted to maintain the spacer means (7) in its blocking position and to oppose the expulsion of the spacer means of the cage.

2. Expansive device according to claim 1, characterized in that the abutment means oppose the lateral expulsion of the spacer means.

3. Expansive device according to any one of claims 1 or 2, characterized in that the abutment means oppose the expulsion of the spacer means (7) by the leading edge (3).

4. Expansive device according to any one of the preceding claims, characterized in that the leading edge (3) comprises a housing (8) for receiving the spacer means (7) so as to cause the height increase of the edge in the blocking position.

5. Expansive device according to any one of the preceding claims, characterized in that the lateral housings (5) are slots arranged along the lateral edges (4) and the spacer means (7) is a rod whose ends (10) ) are adapted to be inserted into the slots (5) forming the lateral housings, the dimensions of the ends of the rod being greater than the thickness of the slots, so that the rod causes an expansion, by elastic deformation, of the thickness of the device at the level where the rod is.

Expanding device according to claim 5, characterized in that the leading edge comprises a slot (9) extending the slots forming the lateral housings (5), said slot being adapted to receive the spacer means (7) so as to cause the leading edge (3) to expand.

7. Device according to any one of claims 4 to 6, characterized in that the housing (8) of the leading edge (3) is constituted by a zone of greater height of the slot (9) of the edge of attack.

8. Device according to any one of claims 5 to 7, characterized in that the slots forming the lateral housing (3) have a decreasing height between the handling edge (2) and the leading edge (3).

9. Device according to any one of claims 5 to 8, characterized in that the abutment means are lateral and located at the ends of the rod (10) engaged with the slots forming the lateral housing (5), said ends being provided with upper diameter lateral stops (11) forming lateral locking means.

10. Device according to any one of the preceding claims, wherein the spacer means comprises two parts (14, 15), characterized in that the part which is on the side of the handling edge (14) is higher than the part which is on the leading edge side (15), so that the portion on the manipulating edge side (14) abuts against the leading edge, opposing the expulsion of the spacer means (7); ) by the leading edge.

11. Device according to the preceding claim, characterized in that the portion (14) of the spacer means (7) which is on the side of the handling edge is between the side edges.

12. Device according to any one of the preceding claims, characterized in that the spacer means comprises a portion between the side edges and having a T-shaped section, the foot of the T cooperating with the walls of the slot (9 ) of the leading edge (3), and the bar of the T abutting against the leading edge (3).

13. Device according to any one of claims 10 to 12, characterized in that the portion (15) of the spacer means which is on the leading edge side has a length equal to that of the leading edge, so that the portion (15) which is on the leading edge side supports the leading edge along its entire length when the spacer means is in the locking position.

14. Device according to the preceding claim, characterized in that the handling edge and the leading edge are longer than the side edges.

15. Device according to any one of the preceding claims, characterized in that the lateral edges (4) are curved.

16. Device according to the preceding claim, characterized in that the lateral edges (4) are shaped so that the posterior lordosis of the device is substantially equal to 4 ° when the spacer means is in the locking position.

Device according to claim 15, characterized in that the lateral edges (4) extend substantially rectilinearly from the handling edge (2) and then curve towards the leading edge (3).

18. Device according to claim 1, characterized in that the leading edge (3) and the lateral edges (4) constitute two tabs (4A, 4B) upper and lower U connected to the edge of manipulation and facing each other. delimiting between them the slit of the leading edge and the lateral housing.

19. Device according to claim 18, characterized in that the upper tongue (4A) comprises a convex upper wall interface with an upper vertebral plateau, the lower tongue (4B) having a concave lower wall interface with a vertebral plateau. inferior.

20. Device according to any one of the preceding claims, characterized in that the cage is made of a piece in one piece.

21. Device according to any one of the preceding claims, characterized in that the cage is PolyÉtherÉtherkétone.

22. Device according to any one of the preceding claims, characterized in that the spacer means (7) is made of a piece in one piece.

23. A surgical method for anterior implantation of an expansive device according to any one of the preceding claims, replacing an intervertebral disc operated between two cervical vertebrae, comprising the following steps:

Difference of the two cervical vertebrae,

Removal of the operated intervertebral disc,

Insertion of the expansive device by its leading edge (3) between the two vertebrae, the expander means (7) of the expansive device being in its insertion position, so that the expansive device occupies the entire surface initially occupied by the operated intervertebral disc,

Placing the spacer means (7) in its locking position.