FR2965169A1 - Intervertebral cage for treating degenerative rachis, has body interposed between two vertebrae, where cavity is realized in body, and crossing cylindrical opening comprising cross section that is on shape of polygonal - Google Patents

Abstract

The cage has a body (10) interposed between two vertebrae. The body comprises two opposite plane base faces (11, 12) and a parallel side wall (13) that connects the two base faces. A cavity (15) is realized in the body while being opened on the base faces. Assembling units (30) assemble a bracket (21) in rotation in the cavity around a rotation axis (16). A crossing cylindrical opening (34) of the assembling units is realized in a shaft (31) such that an axis of the opening is confounded with the rotation axis. A cross section (35) of the cylindrical opening is in a polygonal shape.

Description

INTERVERTEBRAL CAGE

The present invention relates to intervertebral cages finding a particularly advantageous application, but not exclusively, for the treatment of the degenerative spine. An intervertebral cage, especially for the treatment of the degenerative spine, is already known. It essentially comprises a disk-shaped spacer comprising two substantially flat and parallel opposed base faces and a side wall connecting the two base faces. This spacer is adapted to be disposed between the facing faces of the two vertebral bodies respectively of two consecutive vertebrae, replacing the damaged disc located between these two vertebrae, the two base faces of the spacer being placed in contact with the vertebral bodies. . The spacer further comprises an open cavity in which it is possible to place a bone graft or the like in order to weld the two vertebral bodies together by osteosynthesis. Although this achievement generally gives good results, it can, under very exceptional circumstances, not allow the intervertebral cage to perform the role for which it was intended. Indeed, in the first stages following the implantation of the cage, it is noted that during certain relatively large movements of the vertebral column, for example as regards the cervical vertebrae when the head leans very far back. , there can be created a significant space between the base faces of the spacer and the vertebrae, whereby the graft or a part thereof can escape from the cavity in which it was placed. If it is, then the plugin can not play its role properly. Or the absence of effective anchoring generates shear loads which can not immobilize the cage postoperatively, which necessitates a revision surgery. In an attempt to overcome the drawbacks mentioned above, intervertebral cages having an anchor tab pivoting on one side of the spacer have been designed, such as the cage described in US-A-5,683,394.

This embodiment theoretically gives good results but sometimes has shortcomings, especially as to the maintenance of the anchoring tab in its blocking position of the spacer. It has even been proposed an intervertebral cage with two tabs or coverslips, such as that described and illustrated in EP 1 674 053. However, this embodiment is not practical to implement and, moreover, does not allow to use a quantity sufficient grafts to promote and accelerate osteosynthesis between the two vertebrae. Thus, the object of the present invention is to provide an intervertebral cage which overcomes the aforementioned drawbacks of the intervertebral cages described briefly in this preamble, and whose structure also makes possible a very good and reliable anchoring of the cage in the vertebrae between which it must be implanted. More specifically, the subject of the present invention is an intervertebral cage comprising a body capable of being interposed between two vertebrae, said body comprising two substantially flat and parallel opposed base faces and a lateral wall connecting the two base faces, at least one cavity. made in said body by opening on both said base faces, a first tab, and means for mounting the first leg in rotation in said cavity about an axis of rotation substantially parallel to the plane of the base faces between at least two first and second positions, the first position being one in which said first leg is entirely contained in said cavity and the second position being that in which a portion of at least one of the ends of said first leg emerges from said cavity, said means for rotating the first lug having a first rotational shaft integral with the first leg, and a first cylindrical orifice of revolution formed in said body, between said cavity and the side wall, and substantially centered on the axis of rotation, the first rotation shaft being rotatably mounted in said first through hole of way that its axis is substantially coincident with said axis of rotation, characterized in that the means for mounting in rotation the first tab further comprise a first cylindrical through-hole formed in said first shaft so that its axis is substantially coincident with the axis of rotation, the cross section of this first through-hole being polygonal. According to another characteristic of the invention, the intervertebral cage comprises a countersink formed in the end of the first shaft which opens on the side wall of the body, this countersink surrounding the first through-hole and being substantially centered on the axis of rotation, and means for fixing a gripping tool made in cooperation with the counterbore. Other features and advantages of the present invention will become apparent from the following description given with reference to the accompanying drawings for illustrative but not limiting purposes, in which: FIG. 1 is a view from above of a longitudinal section of a embodiment of the intervertebral cage according to the invention, the section according to this figure being referenced II in Figure 2 defined below, Figure 2 is a side view of the intervertebral cage according to the invention in the same mode The embodiment shown in FIG. 1, and FIG. 3 is a schematic partial view of another embodiment of the cage according to the invention, improved with respect to the embodiment according to FIGS. 1 and 2. is first specified that, in the figures, the same references designate the same elements, regardless of the figure on which they appear and whatever the form of representation. these elements. Likewise, if elements are not specifically referenced in one of the figures, their references can be easily found by referring to the other figure. It is also pointed out that the figures essentially represent only one embodiment of the object according to the invention, but that there may be other embodiments which meet the definition of this invention. It is further 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 embodiment described may comprise several of these elements. Conversely, if the embodiment of the object according to the invention as illustrated has several elements of identical function and if, in the description, it is not specified that the object - according to this invention must obligatorily include a particular number of these elements, the object of the invention may be defined as comprising "at least one" of these elements. Lastly, it is specified that when, in the present description, an expression defines, by itself, without a specific particular mention concerning it, a set of structural characteristics, these characteristics may be taken, for the definition of the object of the protection requested, when technically possible, either separately, or in full and / or partial combination. With reference to the two figures 1 and 2 attached, the present invention relates to an intervertebral cage which finds a particularly advantageous application, but not exclusively, for the treatment of degenerative spine. The cage comprises a body 10 adapted to be interposed between two consecutive vertebrae and having two opposite base faces 11, 12 substantially flat and parallel, and a side wall 13 connecting the two base faces. This body is made of, for example titanium or any other biocompatible material, or biodegradable, for example PEEK or the like. The cage also comprises at least one cavity 15 made in the body 10 opening on its two base faces 11, 12, a first tab 21, for example in the form of a blade or the like, and means 30 for mounting said first lug 21 in rotation in the cavity 15 about an axis of rotation 16 substantially parallel to the plane of the base faces 11, 12 between at least two first and second positions, Figure 2.

The first position is that in which the first tab is entirely contained in the cavity 15, FIG. 1, and the second position being that in which a portion 23 of at least one of the ends of the first tab emerges from the cavity in order to be able to anchor in the bone body of the vertebrae. The means 30 for rotating the first lug 21 comprise a first rotary shaft 31 secured to the first lug and a first through hole 32 formed in the body 10, between the cavity 15 and the side wall 13, and being substantially centered. on the axis of rotation 16, the first rotation shaft 31 being rotatably mounted in this first through hole 32 so that its axis is substantially coincident with the axis of rotation 16.

According to an important feature of the invention, these means 30 for rotating the first lug 21 further comprise a first cylindrical through-hole 34 formed in the first shaft 31 so that its axis is substantially coincident with the axis of rotation 16 , the cross section 35 of this first through-hole 34 being polygonal. This feature is very advantageous, especially in the case where the cage has two legs, as shown in both figures. According to another important feature of the invention, these means 30 comprise a countersink 36 formed in the end 37 of the first shaft 31 which opens on the side wall 13 of the body 10, this countersink surrounding the first through-hole 34 and being substantially centered. on the axis of rotation 16, and fixing means 38 of a gripping tool made in cooperation with the countersink 36. Such a gripping tool will be described below in the context of the description of the use of this intervertebral cage.

As an advantageous example, these fastening means 38 of a gripping tool consist of a tapping 39 made in the lateral cylindrical wall of the countersink 36. As mentioned above, quite advantageously, the cage further comprises a second tab 22, means 50 for mounting the second tab in rotation in the cavity 15 about the same axis of rotation 16 as defined above, between at least two first and second positions, the first position being that in which this second tab is entirely contained in the cavity 15 and the second position being that in which part of at least one of the ends of the second tab 22 emerges from the cavity, exactly like the first tab 21 defined above, at least from a functional point of view. The means 50 for rotating the second leg 22 include a second rotation shaft 51 secured to the second leg, and a second cylindrical through hole 52 formed in the body 10, between the cavity 15 and the side wall 13 of the body , this second through-orifice 52 being substantially centered on the same axis of rotation 16, the second shaft 51 then being mounted in rotation in this second through-orifice 52 so that its axis is substantially coincident with this axis of rotation 16. As for the 21, the latter means 50 comprise a second breakthrough 54 made in the second shaft 51 so that its axis is substantially coincident with the axis of rotation 16 and that it opens at least in the cavity 15, the cross section of this second breakthrough 54 being polygonal and having a value at most equal to that of the first throughthrough 34. It is stated that this pierced second 54 must lead into the 15, but not necessarily on the side wall 13 of the body 10, although in Figure 1, it has been shown therein. The illustrated embodiment is advantageous because, as a result, the two leg / shaft assemblies can be identical before the counterbore 36 is made in the shaft corresponding to the first leg, which reduces the manufacturing cost of the cage.

According to a preferred embodiment, the transverse sections respectively of the first and second bores 34, 54 are identical, optionally of polygonal shape "hexagon". Advantageously, the cage further comprises means 60 for limiting the amplitude of the rotation of the first lug 21 relative to the body 10 which, according to a preferred embodiment, comprise at least one circular groove 62 formed in the outer wall of the first shaft. 31 being inscribed in an angle R defined by the first and second positions of the first tab, in this case generally of the order of ninety degrees, as shown in Figure 2. These means 60 further comprise a hole 63 pierced in the body 10 and opening facing the circular groove 62 and on the side wall 13 of the body, and a pin 64 disposed in the hole 63 and able to plunge into the circular groove 62. Still preferentially , the cage further comprises means 70, 70 'for locking the first lug 21 when it is in its second position P2. These means can be of different shapes and structures. For example as shown in 70 'in the figures, they may be constituted by a screw which passes through the body 10 to open into the cavity and be placed behind the tab when it is in its second position. However, as illustrated at 70 in the figures, these means 70 for locking the first lug 21 when it reaches its second position P2 15 are very advantageously constituted by a housing 71 formed at the end of the circular groove 62 located opposite the hole 63 when the first tab 21 is in its second position, this housing 71 being adapted to receive the penetrating end 72 of the pin 64 by a further depression thereof in the hole 63. Preferably, the cage comprises also means 160 for limiting the amplitude of rotation of the second leg 22, constituted by at least one other circular groove 162 formed in the outer wall of the second shaft 51 and inscribed in an angle (3 '(which is generally the same). that the angle R defined above) defined by the first and second positions of the second leg 22, another hole 163 pierced in the body and opening opposite this other groove. e circular and on the side wall 13 of the body, and another pin 164 disposed in this other hole and able to plunge into the other circular groove. As for the first leg 21, the cage comprises means for blocking the second leg 22 when it arrives in its second position, preferably constituted by another housing made at the end of the other circular groove located opposite the other hole 163 when the second leg 22 is in its second position, this other housing being adapted to receive the penetrating end of the other pin 164 by an additional depression thereof in the other hole 163. According to another feature of the invention, the intervertebral cage comprises means for crimping at least one of the two shafts 31, 51, at the outlet of the orifice 32, 52 in which it is located, on the side wall 13 of the body 10 to fix the lug / shaft assembly on the body 10, while allowing the rotation of the shaft in the corresponding cylindrical orifice of revolution. These latter means are well known in themselves and will not be further described herein since they are within the skill of the art. It is added that the intervertebral cage as described above is more particularly adapted for its implantation according to the so-called "anterior approach" technique. However, optionally, so that it can be used for implantation by another way, the means 30 for rotating at least the first leg 21 (and advantageously the two legs 21, 22 at the same time) comprise in in addition to means 400 for flair pivoting the tab by one of its ends. The latter means 400, FIG. 3, which represents the cage when the lugs 21, 22 are in their first position P1, may consist, for example, of a rod 401 rotatably mounted laterally in the body 10 along an axis 402 parallel to the 16 'axis of rotation defined above, and emerging from the body by at least one of its ends, and by means for coupling this rod 401 with one end of each of the two tabs 21, 22. These coupling means are for example of the "rack" type and comprise notches 403 (schematically illustrated) or the like so that, when the rod 401 is rotated R1 about its axis 402, it causes the rotation R2 of the two legs 21, 22 by their End, in an amplitude sufficient to emerge both at least partially from the cavity 15 and take their second position P2.

The intervertebral cage according to the invention as described above is used as follows: It is firstly mentioned that the cage as described above is manufactured in the factory, and usually arrives at the surgeon practitioner under blister and sterilized, the tabs 21, 22, such as blades or the like, being arranged in their first position P1. As for the two breakthroughs 34, 54, they are made so that their cross sections are on the same cylindrical shell Ec, Figure 1. The Practitioner also has at his disposal an ancillary laying Ap essentially consisting of an outer tube Te one of which end has its outer surface threaded complementary to the tapping 39 of the counterbore 36, and an inner central tube Tc (for example of the "hexagonal key" type) having the same cross-sectional area as the cross section of the bores 34, 54, so that it can be plunged into the two holes 34, 54. These two tubes Te and Tc are designed so that the tube Tc can at least slide in the tube Te, and even rotate there. When the Practitioner wants to implant such a cage, after having released the blister, it screws the end of the tube Te in the counterbore 36 by holding the body 10 and the legs 21, 22 by any means, for example a clamp or the like , the legs being always maintained in their first position P1. Then, it slides the tube Tc in the tube Te and in the two breakthroughs 34, 54. It is also possible to introduce first the central hexagonal key Tc, the progress of which is stopped by a stop in the breakthrough 54 of the second tab 22, then slide on this key, the tube Te which plays the role of gripper and which is screwed into the tapping 38. At the end of screwing, the tip of the tube Te gripper bears on, for example , a shoulder of the central key, which imprisons in pressure the latter. Thus, in the end, the cage and the anchoring device Ap are firmly connected during the insertion of the cage between the vertebrae. When the cage is connected to the ancillary as defined above, the practitioner can then, in known manner, introduce the cage between the two vertebrae until it takes the desired position by him. In known manner, he will generally have previously taken care to fill the cavity of one or more bone grafts or the like. Then, it can then act on the tube Tc to rotate the tabs 21, 22 so that they pass from their first position P1 to their second position P2 and thus be introduced respectively into the two vertebral bodies of the two vertebrae, such as the paws or blades of the same intervertebral cages of the prior art. It should be noted that the pin or pins 64, 164 and the grooves 62, 162 allow the practitioner to determine without difficulty, and unequivocally, the two positions P1 and P2 of the legs, which is very convenient, since he does not have direct visual access to the cage when it is implanted, except by radiography, which makes it possible to avoid prolonged use of it. It is also possible, for greater security, that the hexagonal key is indexed angularly, which allows the practitioner to know at every moment the position of the legs relative to the body 10. When this phase of setting up the cage is completed, it can act in force on the pins 64, 164 so that they sink into their corresponding housing 71, to permanently block the tabs in their second position P2. It can complete this blocking by introducing, for example, a screw on the front of the body 10 according to the optional means 70 'described above. Finally, by holding the tube Tc, the practitioner unscrews the tube Te, then removes the two tubes Tc and Te. The cage is then definitely implanted.

Claims (7)

REVENDICATIONS1. Intervertebral cage comprising: - a body (10) adapted to be interposed between two vertebrae, said body having two substantially flat and parallel opposed base faces (11, 12) and a side wall (13) connecting the two base faces, - at least one cavity (15) formed in said body (10) opening on both said base faces (11, 12), - a first leg (21), and 10 - means (30) for mounting the first leg (21) rotating in said cavity (15) about an axis of rotation (16) substantially parallel to the plane of the base faces between at least two first and second positions, the first position (P1) being that in which said first tab is entirely contained in said cavity (15) and the second position (P2) 15 is that in which a portion (23) of at least one end of said first tab emerges from said cavity, said means (30) to rotate the first leg comprising: a first rotary shaft (31) secured to the first leg (21), and a first cylindrical through hole (32) formed in said body (10), between said cavity (15) and the side wall ( 13), and substantially centered on the axis of rotation (16), the first rotation shaft (31) being rotatably mounted in said first through hole (32) so that its axis is substantially coincident with said axis of rotation 25 (16), characterized in that the means (30) for rotating the first leg (21) further comprise: - a first cylindrical through-bore (34) formed in said first shaft (31) so that its axis is substantially coincident with the axis of rotation (16), the cross section (35) of this first through-hole (34) being polygonal. 2. Cage according to claim 1, characterized in that the means (30) for rotating the first leg (21) further comprises: - a countersink (36) formed in the end (37) of said first shaft (31) which opens on the side wall (13) of said body (10), said countersink surrounding said first through-hole (34) and being substantially centered on said axis of rotation (16), and - fastening means ( 38) of a gripping tool made in cooperation with said countersink (36). 3. Cage according to one of claims 1 and 2, characterized in that the fastening means (38) of a gripping tool consist of a tapping (39) formed in the side cylindrical wall of said counterbore ( 36). 4. Cage according to one of claims 1 to 3, characterized in that it further comprises: - a second leg (22) - means (50) for mounting the second leg in rotation in said cavity (15) ) around said axis of rotation (16) between at least two first and second positions, the first position being that in which said second tab is entirely contained in said cavity (15) and the second position being that in which part of the at least one end of said second tab (22) emerges from the cavity, said means (50) for rotating the second tab comprising: * a second rotation shaft (51) integral with the second tab (22) and a second cylindrical through hole (52) formed in said body (10) between said cavity (15) and the body side wall (13), said second through hole (52) being substantially centered on said axis rotation (16), the second shaft (51) being rotated in said second through hole (52) so that its axis is substantially coincidental with said axis of rotation, and * a second bore (54) formed in said second shaft (51) so that its axis is substantially merged with the axis of rotation (16) and that it opens at least in said cavity (15), the transverse section of this second bore (54) being polygonal and having a value at most equal to that of the first through-hole (34). ). 5. Cage according to claim 4, characterized in that the cross sections respectively of the first and second bores (34, 54) are identical, preferably of polygonal shape "hexagon". 6. Cage according to one of the preceding claims, characterized in that it further comprises means (60) for limiting the amplitude of rotation of said first tab (21) relative to said body (10). 7. Cage according to claim 6, characterized in that the means (60) for limiting the amplitude of the rotation of said first tab (21) relative to said body (10) comprise: - at least one circular groove (62) formed in the outer wall of said first shaft (31), said circular groove being inscribed in an angle (R) defined by the first and second positions of said first leg, 15 - a hole (63) drilled in said body (10) and opening opposite said circular groove (62) and on the lateral wall (13) of said body, and - a pin (64) disposed in said hole (63) and able to plunge into said circular groove (62) ). 10. Cage according to one of the preceding claims, characterized in that it further comprises means (70, 70 ') for locking said first tab (21) when it is in its second position. 11. Cage according to claims 7 and 8, characterized in that the means (70) for locking said first tab (21) when it arrives in its second position are constituted by a housing (71) made at the end of the circular groove (62) located opposite the hole (63) when said first tab (21) is in its second position, said housing (71) being adapted to receive the penetrating end (72) of the pin (64) by an additional depression thereof in the hole (63). 12. Cage according to one of the preceding claims when it depends on claim 4, characterized in that it comprises means (160) for limiting the amplitude of the rotation of said second tab (22), these means being constituted by: - at least one other circular groove (162) formed in the outer wall of said second shaft (51), said other circular groove being inscribed in an angle (0 "defined by the first and second positions of said second leg (22), another hole (163) pierced in said body and opening opposite said other circular groove and on the side wall (13) of said body, and - another pin (164) disposed in said other hole and suitable to dive into said other circular groove 11. Cage according to one of the preceding claims when it depends on claim 4, characterized in that it comprises means for blocking said second tab (22) when it arrives in its second position, these means being constituted by another housing formed at the end of the other circular groove located opposite the other hole (163) when said second tab is in its second position, said other housing being adapted to receiving the penetrating end of the other pin (164) by further depressing it into the other hole (163). 12. Cage according to one of the preceding claims when it depends on claim 4, characterized in that it comprises means for crimping at least one of the two shafts (31, 51) at the outlet of the orifice (32, 52) in which it is located, on the side wall (13) of the body (10) for fixing the leg / shaft assembly on the body (10), while allowing the rotation of the shaft in the corresponding cylindrical orifice of revolution. 13. Cage according to one of the preceding claims, characterized in that the means (30) for rotating the first leg (21) further comprises means (400) for pivoting by one of its two ends.