Intervertebral cage

Abstract

The present invention relates to interbody cages suitable for interposing between two vertebral bodies. The cage comprises an element 10 having the general shape of a disc having two substantially parallel opposite faces 11, 12, the two opposite faces being suitable for coming into contact respectively with the two vertebral bodies by defining two facial planes containing these two faces 11, 12 to delimit a space 26 between these two faces; and means for locking the element 10 with the two vertebral bodies, these locking means being constituted by first fixing means suitable for fixing the element 10 on one of the two vertebral blocks, second fixing means suitable for fixing said element 10 on the other of the two vertebral blocks, the first and second fixing means being suitable for being operational independently of each other.

Description

Title of the invention: Intervertebral cage technical field

[0001] The present invention relates to intersomatic cages suitable for being interposed between two vertebrae in replacement of the intervertebral disc originally located between these two vertebrae, of the type comprising an element having the general shape of a substantially cylindrical disc and means of locking this element with the two vertebrae by means of blades in order to obtain the fixation of the cages by osteosynthesis.

[0002] Interbody cages are known to include a disc and means for locking this disc with the two vertebrae between which it is placed, these locking means being made up of blades capable of pivoting so that their ends are embedded in the bony element of the vertebrae.

[0003] Such a cage is for example described and illustrated in FR2955483. It gives good results but does not allow for the practical resolution of cases such as spondylolisthesis (namely the case where the vertebrae are not aligned).

[0004] Also, the present invention aims to produce an interbody cage which overcomes the disadvantages of the prior art cages mentioned above while facilitating the work of practitioners.

[0005] More specifically, the present invention relates to an interbody cage suitable for interposing between a first vertebral body and a second vertebral body in place of the intervertebral disc initially present between these two vertebral bodies, the cage comprising: an element having the general shape substantially of a disc having two substantially parallel opposite faces, the two said opposite faces being suitable for coming into contact respectively with the two vertebral bodies by defining two facial planes containing these two faces to delimit a space between these two faces and means for locking said element with the two vertebral bodies, characterized in that these locking means consist of first means of fixing suitable for fixing said element on one of the two vertebral blocks and second means of fixing suitable for fixing said element on the other of the two vertebral blocks,said first and second fastening means being capable of being operational independently of each other.

[0006] Other features and advantages of the invention will become apparent from the following description given with reference to the accompanying drawings, which are by way of illustration but in no way limiting, in which:

[0007] Figure [1] represents a schematic top view of a preferred embodiment of the interbody cage according to the invention,

[0008] Figure [Fig. 2] represents a portion of the cage according to the invention in the embodiment according to Figure [1], in a first configuration considered to be initial,

[0009] Figure 3 represents the same part of the cage according to the invention as that shown in Figure 2, but in a second configuration,

[0010] Figure 4 represents the same part of the cage according to the invention as that shown in Figure 2, but in a third configuration,

[0011] Figure 5 represents the same part of the cage, but in a fourth configuration considered to be final,

[0012] Figure 6 represents a very schematic top view of a second possible embodiment of the interbody cage according to the invention,

[0013] Figure 7 represents a very schematic top view of a third possible embodiment of the interbody cage according to the invention,

[0014] Fig. 8 represents four very schematic views referenced chronologically (1) to (4) illustrating a method of implanting the interbody cage according to the invention, particularly for the treatment of spondylolisthesis.

[0015] It is specified that, when, according to the definition of the invention, the object of the invention comprises “at least one” element having a given function, the described embodiment may comprise several of these elements. Conversely, if the embodiment of the object according to the invention as illustrated comprises several elements with identical functions and if, in the description, it is not specified that the object according to this invention must necessarily comprise a particular number of these elements, the object of the invention may be defined as comprising “at least one” of these elements.

[0016] It is specified that when, in the present description, an expression defines by itself, without any particular specific mention concerning it, a set of structural characteristics, these characteristics may be taken, for the definition of the object of the protection sought, when this is technically possible, either separately, or in total and / or partial combination.

[0017] It is further specified that, in the present description, if the adverb "sensiblement" is associated with a qualifier of a given means, this qualifier must be understood in the strict or approximate sense.

[0018] With regard to the attached figures, the present invention relates to an interbody cage suitable for being interposed between two vertebral bodies VI, V2 in replacement of the intervertebral disc originally located between these two vertebral bodies.

[0019] This cage comprises an element 10 having the general shape substantially of a disc having two substantially parallel opposite faces 11, 12, these two opposite faces being able to come into contact respectively with the two vertebral bodies VI, V2 by defining two facial planes containing these two opposite faces to delimit a space 26 ([Fig.8](4)) included between these two faces and means of blocking the element 10 with the two vertebral bodies.

[0020] According to the primary function of the cage according to the invention, these locking means consist of first fixing means suitable for fixing the element 10 on one of the two vertebral bodies VI, V2 and second fixing means suitable for fixing this same element 10 on the other of the two vertebral bodies V2, VI, specifying that these first and second fixing means are suitable for being operational independently of each other, as will be shown below in the continuation of this description.

[0021] According to a first feature of the invention, the first fixing means comprise a first connecting means capable of securing the element 10 to the first vertebral body VI without this element 10 being secured to the second vertebral body V2, and the second fixing means comprise a second connecting means capable of securing this same element 10 to the second vertebral body V2 after it has been secured to the first vertebral body VI.

[0022] According to another feature of the invention, at least one of the two connecting means defined above comprises at least a rotating shaft 21, 22, 40, figures 1 and 6, capable of being pivoted relative to the element 10, a first portion of blade 24, 28, 41, 45 and means for securing this first portion of blade to the rotating shaft so that it is capable of taking any position between a first position and a second position, the first position being that in which, according to a first angular position of the rotating shaft relative to the element 10, this first portion of blade is entirely contained within the space 26 and the second position being that in which, according to a second angular position of the rotating shaft relative to the element 10, the first portion of blade emerges at least partially only from one first side of this space 26, but not from the opposite side.

[0023] Advantageously, at least one of the two connecting means defined above comprises a second portion of blade 41, 45 and means for securing this second portion of blade to the rotation shaft 21, 22, 40 so that it is also able to take any positions between a first position and a second position, the first position being that in which, according to the first angular position of the shaft, this second portion of blade is entirely contained within the space 26 and the second position being that in which, according to the second angular position of the shaft 21, 22, 40, this second portion of blade emerges at least partially only from the second side, opposite to the first side, of the space 26, as defined above.

[0024] More particularly, as illustrated in [Fig. 7], the rotation shaft defining a longitudinal axis 47 consists of two half-shafts 40-1, 40-2, these two half-shafts being mounted cooperatively to each other so as to be able to slide relative to each other to the other along this longitudinal axis 47, each half-shaft 40-1, 40-2 supporting at least one portion of blade 41, 45.

[0025] In addition, for the embodiment according to [Fig. 7], means are provided for locking the two half-shafts 40-1, 40-2 in position after they have been slid relative to each other as will be explained below. These means for locking the two half-shafts in position are, for example, a ratchet, a pin, or the like. These means, referenced as 50, have only been illustrated very schematically, since their construction is well known to those skilled in the art.

[0026] According to another feature, the first and second connecting means comprise, [Fig.1], a single shaft 40 mounted in rotation relative to the element 10, at least one portion of a blade 41 called the "third portion of the blade", and means for securing this third portion of the blade 41 to the single shaft 40 so that it is able to take any position between a first position and a second position, the first position being that in which, according to a first angular position of the single shaft 40 relative to the element 10, the third portion of the blade 41 is entirely contained within the space 26 defined between the two facial planes, the second position being that in which, according to a second angular position of the single shaft 40 relative to the element 10 after a rotation of this single shaft in a first direction of rotation, the third portion of the blade 41 emerges at least partially from a first side of the space 26.

[0027] The first and second connecting means further comprise at least one other portion of blade 45 called "fourth portion of blade", and means for mounting this fourth portion of blade 45 in cooperation with the single shaft 40 so that it is able to take any positions between a first position and a second position, the first position being that in which, according to a first angular position of the single shaft, this fourth portion of blade 45 is entirely contained within the space 26, the second position being that in which, according to a second angular position of the single shaft in a second direction of rotation opposite to the first direction of rotation of this single shaft, the fourth portion of blade 45 emerges at least partially from the second side of the space 26, opposite to the first side of this same space 26.

[0028] According to an advantageous embodiment, the means for mounting the third 41 and fourth 45 blade portions in cooperation with the single shaft 40 comprise means for driving the rotation of the third blade portion 41 when the single shaft 40 undergoes a rotation in the first direction of rotation, without driving the fourth blade portion 45 into rotation, and means for driving the rotation of the fourth blade portion when the single shaft 40 undergoes a rotation in the opposite direction of the first direction of rotation, without driving the third blade portion 41 into rotation.

[0029] The means for driving the rotation of at least one of the third and fourth blade portions consist of the fact that one of the third and fourth blade portions is mounted in rotation on the shaft via a free bearing in cooperation with coupling means comprising an oblong slot 51 made in the single shaft 40 or in the bearing and a finger 52 mounted projecting on the bearing or on the single shaft, so that this finger 52 is able to travel the oblong slot 51 so that, according to a direction of rotation of the single shaft 40, one of the third and fourth blade portions is subjected to a rotation when the finger comes against an end of the oblong slot 51.

[0030] It is specified that this oblong slot 51 can be formed in a plane perpendicular to the axis of the shaft 40 (as illustrated in Figures 2-5), but that it can also be formed in a plane with a certain inclination to the axis, the means for mounting the portion of the blade on the shaft 40 being then adapted accordingly. This oblong slot can also have a curved profile.

[0031] Figures 2 to 5 illustrate the operation of these means in the embodiment described above.

[0032] Figure 2 illustrates the original position of the two blade portions 41, 45 defined as being their first position in space 26, the fingers 52 being arranged in the slots 51 as illustrated in this figure.

[0033] When the shaft 40 is pivoted in the dextrorsum direction, [Fig.3], the portion of blade 41 pivots, but not the portion of blade 45, since the finger 52 travels through the slot 51 made in this portion of blade 45 without driving it.

[0034] When the shaft 40 is pivoted in the sinistrorsum direction, [Fig.4], the portion of the blade 45 pivots, but not the portion of the blade 41, since the finger 52 travels along the slot 51 made in this portion of the blade 41 without driving it.

[0035] The final position, defined as the second position above, is illustrated in [Fig.5], in which it is easy to understand that the two blades 41, 45 may have been implanted successively in the two vertebral bodies VI, V2, to obtain a result which will be explained below with regard to the four diagrams in [Fig.8].

[0036] In the description given above, only one portion of the blade 41, 45 is mentioned on either side of the rotation shaft 40. However, according to an advantageous and preferred embodiment, at least one of the two connecting means, preferably both, further comprises a fifth portion of the blade 28, 24, [Fig. 1], 6, 7, 8, and means for securing this fifth portion of the blade to the rotation shaft so that it is capable of assuming any position between a first position and a second position, the first position being that in which, according to a first angular position of the rotation shaft relative to the element 10, the fifth portion of blade 28, 24 is entirely contained within space 26 and the second position being that in which, according to a second angular position of the rotation shaft relative to element 10, the fifth portion of blade 28, 24 emerges at least partially only from the first side of space 26, the first and fifth portions of blade 24, 28 being substantially opposite each other on the same side of this shaft making a non-zero angle between them to obtain, after their implantation in the vertebral body, a wedge effect fixation.

[0037] According to a preferred embodiment of the cage, the element 10 has a substantially central through cavity 30 opening respectively onto the two opposite faces 11, 12 of this element, the fixing means being located at least partially in the cavity 30, as illustrated in [Fig.1].

[0038] Fig. 8 represents in a very schematic way a method of implanting the cage according to the invention in the case of the treatment of a deformity of a vertebral column such as spondylolisthesis between two consecutive vertebrae VI, V2, for example following an accident.

[0039] Fig. 8(l) represents a first step in the treatment: the placement of element 10 in place of the intervertebral disc which was located between the two vertebrae.

[0040] Fig. 8(2) represents a second stage of the treatment: the fixation of element 10 with only one of the two vertebrae, in this case vertebra VI, by rotating the two portions of blade 24, 28 located on the same side of the rotation shaft 40 to implant them in the vertebral body VL. In this second stage, the vertebral body VI and element 10 are fixed relative to each other.

[0041] Fig. 8(3) represents a third stage of treatment: the translation of the second vertebra V2 until it is positioned along the original physiological axis of the vertebral column in order to relieve the patient's pain,

[0042] Fig. 8(4) represents the final stage of the treatment where portions of the blade like that referenced 41 as opposed to those referenced 24, 28 were ordered to be implanted in the vertebral body V2 and block it in relation to element 10.

[0043] With vertebral bodies VI and V2 both fixed to element 10 and aligned with each other, the site of the patient's pain must be eliminated.

[0044] Fig. 6 represents another embodiment of the cage according to the invention, with which the implantation method is deduced from that described above, the only difference being that the two rotation shafts 21, 22 can be pivoted simultaneously or successively in two opposite directions.

[0045] Figure 7 represents an embodiment of the cage according to the invention, in which the implantation method consists of inserting element 10 between the two vertebral bodies subjected to spondylolisthesis. The two half-trees are controlled The shaft is rotated so that the two pairs of blade portions located on the two half-shafts 40-1 and 40-2 are implanted respectively into the two misaligned vertebral bodies. Then, half-shaft 40-1, secured to vertebral body V2, is slid relative to half-shaft 40-2 until vertebral body V2 is aligned with vertebral body VI along the original axis of the vertebral column. After these two bodies have been aligned, the two half-shafts are fixed to each other using means 50.

Claims

Demands

1. An interbody cage suitable for interposing between a first vertebral body (VI) and a second vertebral body (V2) in replacement of the intervertebral disc initially present between these two vertebral bodies, the cage comprising: an element (10) having the general shape substantially of a disc having two substantially parallel opposite faces (11, 12), the two said opposite faces being suitable for coming into contact respectively with the two vertebral bodies (VI, V2) by defining two facial planes containing these two faces (11, 12) to delimit a space (26) included between these two faces;and means for locking said element (10) with the two vertebral bodies, characterized by the fact that these locking means consist of: • first means of fixation capable of fixing said element (10) on one of the two vertebral blocks (VI, V2), • second means of fixation capable of fixing said element (10) on the other of the two vertebral blocks (V2, VI), • said first and second means of fixation being capable of being operational independently of each other.

2. Interbody cage according to claim 1, characterized in that the first means of fixation comprise a first means of connection capable of securing said element (10) to the first vertebral body (VI) without said element (10) being secured to the second vertebral body (V2) and that the second means of fixation comprise a second means of connection capable of securing said element (10) to the second vertebral body (V2) after it has been secured to said first vertebral body (VI).

3. Interbody cage according to claim 2, characterized in that at least one of the two connecting means comprises: • at least one rotation shaft (21, 22, 40) capable of being pivoted relative to said element (10), • a first blade portion (24, 28, 41, 45), and • means for securing said first blade portion to said rotation shaft so that it is capable of assuming any positions between a first position and a second position, the first position being that in which, according to a first angular position of said rotation shaft relative to said element (10), said first portion of blade is entirely contained within said space (26) and the second position being that in which, according to a second angular position of said rotation shaft with respect to said element (10), said first portion of blade emerges at least partially only from one first side of said space (26).

4. Interbody cage according to claim 3, characterized in that said at least one of the two connecting means comprises a second portion of blade (41, 45) and means for securing this second portion of blade to said rotation shaft (21, 22, 40) so that it is able to take any positions between a first position and a second position, the first position being that in which, according to said first angular position of said shaft, said second portion of blade is entirely contained within the space (26) and the second position being that in which, according to said second angular position of said shaft (21, 22, 40), this second portion of blade emerges at least partially only from the second side, opposite said first side, of said space (26).

5. Interbody cage according to any one of claims 2 to 4, characterized in that said rotation shaft defining a longitudinal axis (47) is made up of two half-shafts (40-1, 40-2), these two half-shafts being mounted cooperatively with respect to each other so as to be able to slide with respect to each other along said longitudinal axis (47), each half-shaft (40-1, 40-2) supporting at least one portion of blade (41, 45).

6. Cage according to claim 2, characterized in that the first and second connecting means comprise: • a single shaft (40) mounted for rotation with respect to said element (10), • at least one blade portion (41) referred to as the "third blade portion", • means for securing said third blade portion (41) to said single shaft (40) so that it is capable of assuming any position between a first position and a second position, the first position being that in which, according to a first angular position of said single shaft (40) with respect to said element (10), said third blade portion (41) is entirely contained within the space (26) defined between the two facial planes, the second position being that in which, according to a second position

7.

8. angular of the said single shaft (40) with respect to the said element (10) after a rotation of the said single shaft in a first direction of rotation, the said third portion of blade (41) emerges at least partially from a first side of the said space (26), • at least one other portion of the blade (45) referred to as the "fourth portion of the blade, • means for mounting said fourth portion of blade (45) in cooperation with said single shaft (40) so that it is able to take all positions between a first position and a second position, the first position being that in which, according to a first angular position of said single shaft, said fourth portion of blade (45) is entirely contained in the space (26), the second position being that in which, according to a second angular position of said single shaft in a second direction of rotation opposite to said first direction of rotation of said single shaft, said fourth portion of blade (45) emerges at least partially from the second side of said space (26), opposite to said first side of said space (26). Cage according to claim 6, characterized in that the means for mounting said third (41) and fourth (45) blade portions in cooperation with said single shaft (40) comprise means for driving the rotation of said third blade portion (41) when the single shaft (40) undergoes a rotation in the first direction of rotation, without driving the fourth blade portion (45) into rotation, and means for driving the rotation of the fourth blade portion when the single shaft (40) undergoes a rotation in the opposite direction of said first direction of rotation, without driving the third blade portion (41) into rotation. Cage according to claim 7, characterized in that the means for driving the rotation of at least one of the third and fourth blade portions consist of said one of the third and fourth blade portions being rotationally mounted on the shaft via a free bearing in cooperation with coupling means comprising an oblong slot (51) formed in the single shaft (40) or in the bearing and a finger (52) projecting from the bearing or the single shaft, such that this finger (52) is able to travel along said oblong slot (51) so that, in a direction of rotation of said single shaft (40), one of the third and fourth portions of the blade are subjected to rotation when said finger comes against one end of said oblong slot (51).

9. Cage according to any one of the preceding claims when it depends on claim 3, characterized in that at least one of the two connecting means further comprises a fifth blade portion (28, 24) and means for securing this fifth blade portion to said rotation shaft so that it is capable of assuming any positions between a first position and a second position, the first position being that in which, according to a first angular position of said rotation shaft relative to said element (10), said fifth blade portion (28, 24) is entirely contained within said space (26) and the second position being that in which, according to a second angular position of the rotation shaft relative to said element (10), said fifth blade portion (28, 24) emerges at least partially only from the first side of the space (26), the first and fifth blade portions (24,28) being substantially opposite each other on the same side of this tree, forming a non-zero angle between them.

10. Cage according to any one of the preceding claims, characterized in that said element (10) comprises a substantially central through cavity (30) opening respectively onto the two said opposite faces (11, 12) of said element (10), said fastening means being located at least partially in said cavity (30).

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