FR3154311A1 - intervertebral cage - Google Patents

Abstract

The present invention relates to intervertebral cages. The cage comprises an element 10 comprising at least one locking blade 20, means for rotating the blade 20 about an axis 21 so that this blade is able to take any position between a first position and a second position P2, these means for rotating the blade comprising a shaft 24 rotatably mounted relative to the element about the axis 21 and means for connecting the blade to the shaft 24, these means comprising a male spherical zone 31 formed in cooperation with the shaft 24, a through-hole 32 formed in the blade 20, having the shape of a female spherical zone 33 able to pivot relative to the zone 31 by a given central angle value Ad, and means for securing the blade 20 to the shaft 24. Figure 1

Description

intervertebral cage

The present invention relates to intervertebral cages capable of being interposed between the bodies of vertebrae to replace intervertebral discs.

We already know of such an intervertebral cage, the one described and illustrated in FR2955483 in the name of the same Applicant.

This intervertebral cage is essentially characterized by the fact that it comprises a shaft for rotating an anchoring blade in a plane making a first angle with the planes passing respectively through the two opposite faces of a substantially disc-shaped element. This angle is, in this embodiment, different from ninety degrees and, as a result, the blade has a certain inclination relative to the axis of the rotation shaft.

The technical problem that can arise with this method of producing such a cage is essentially the production of the assembly, and therefore the assembly of the shaft and the blade according to the desired inclination.

The present invention therefore aims to remedy this situation by proposing a solution which facilitates this achievement in particular and which, in addition, can offer possibilities for more easily obtaining different values of inclination of the blade relative to the axis of the rotation shaft.

More specifically, the present invention relates to an intervertebral cage capable of being interposed between two vertebral bodies to replace the intervertebral disc originally located between the two vertebrae, comprising: an element having the general shape of a disc comprising two substantially parallel opposite faces and a lateral wall connecting said two opposite faces, these opposite faces being capable of coming into contact respectively with the two vertebral bodies and substantially defining two planes which contain them; at least one locking blade, the overall width of this blade, measured in the plane substantially perpendicular to the two opposite faces, being at most equal to the distance separating these two opposite faces and its overall length measured in this same plane being greater than this distance; means for rotating said blade about an axis so that this blade is able to take any position between a first position and a second position, the first position being that in which the blade is entirely contained in the space defined between the planes of the two opposite faces and the second position being that in which at least one end of the blade emerges from this space, these means for rotating the blade comprising a shaft mounted rotatably relative to the element about said axis and means for connecting the blade with said shaft, characterized in that the means for connecting the blade with said shaft comprise a male spherical zone produced in cooperation with said shaft, the radius of this male spherical zone having a determined value, a through-hole produced in said blade, the inner wall of which has the shape of a female spherical zone, the radius of this female spherical zone having a value at least equal to the value of the radius of the male spherical zone so that said female spherical zone is able to pivot relative to said male spherical zone by a central angle value given, and means for securing said blade to said shaft in a given angular position relative to said axis of rotation.

Other characteristics and advantages of the invention will appear during the following description given with reference to the attached drawings for illustrative but in no way limiting purposes, in which:

There FIG. 1 represents a diagram, according to a first sectional plane, of a first embodiment of the cage according to the invention,

There FIG. 2 represents a diagram, according to a second section plane perpendicular to the first section plane, of the first embodiment,

There FIG. 3 represents a diagram making it possible to explain the principle of a second embodiment of the cage according to the invention, and

There FIG. 4 represents this second preferred embodiment in more detail of the cage according to the invention, applying the teaching of the FIG. 3 .

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 embodiment described may comprise several of these elements. Conversely, if the embodiment of the object according to the invention as illustrated comprises several elements of identical function 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.

It is specified that when, in this description, an expression defines on its own, without any 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 this is technically possible, either separately, or in total and/or partial combination.

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

It should also be noted that, in all four figures, the same references designate the same means having the same function, regardless of their graphic representation.

Furthermore, it is clearly stated that, by "spherical zone", is understood the portion of the surface of a sphere between two parallel planes which intersect this sphere, and that a diametrical plane is a plane which passes through the center of the sphere.

Furthermore: two spherical zones, respectively male and female, can be said to be complementary when they are able to pivot relative to each other without their respective spherical surfaces necessarily sliding over each other, it then being possible for there to exist between them a non-zero space, but of sufficiently small value so that these two surfaces are nevertheless considered, within the meaning of the present invention, as complementary.

As mentioned above, the present invention relates to intervertebral cages capable of being interposed between two vertebrae to replace the intervertebral disc originally located between these two vertebrae.

According to the present invention, the cage comprises an element 10 having the general shape of a disc comprising two opposite faces 11, 12 which are substantially parallel and a side wall connecting the two opposite faces, these opposite faces being able to come into contact respectively with the two vertebral bodies and substantially defining two planes which contain them; at least one locking blade 20, the overall width of this blade, measured in the plane substantially perpendicular to the two opposite faces, being at most equal to the distance separating these two opposite faces and its overall length measured in this same plane being greater than this distance; means for rotating the blade 20 around an axis 21 so that this blade is able to take any position between a first position P1 and a second position P2, the first position P1 being that in which the blade is entirely contained in the space defined between the planes of the two opposite faces 11, 12 and the second position P2 being that in which at least one end 22 of the blade emerges from this space, these means for rotating the blade comprising a shaft 24 mounted to rotate relative to the element around the axis 21 and means for connecting the blade with the shaft.

According to a characteristic of the invention, the means for connecting the blade with the shaft comprise: a male spherical zone 31 produced in cooperation with the shaft, the radius of this male spherical zone having a determined value; a through-hole 32 produced in the blade 20, the inner wall of which has the shape of a female spherical zone 33, the radius of this female spherical zone having a value at least equal to the value of the radius of the male spherical zone 31 so that the female spherical zone is able to pivot relative to the male spherical zone 31 according to a given central angle value Ad; and means for securing the blade 20 with the shaft 24 in a given angular position relative to the axis of rotation 21.

The male spherical zone can be mounted in cooperation with the shaft 24 in different ways, either by being produced in one piece with the shaft by machining, molding, etc., or by being produced independently and then added and fixed on the shaft in different ways, for example by welding or the like, possibly in one or more combinable parts. Furthermore, preferably, this male spherical zone 31 is substantially centered on the axis 21 of the shaft 24.

Figures 2 and 3 illustrate a first embodiment applying the general definition of the structure of the cage according to the invention given above.

According to this first embodiment, the cage comprises two substantially complementary spherical zones 31, 33 whose spherical surfaces in contact are capable of sliding over one another. As a result, the two spherical zones have substantially the same radius of curvature. However, the value of the radius of the female spherical zone will be very slightly greater than the value of the radius of the male spherical zone, so as to ensure the pivoting of the two zones relative to one another.

With this structure, the blade 20 can therefore be positioned according to a desired angulation relative to the axis 21 of the rotation shaft 24, so as to obtain a result as for example explained in the document FR2955483 mentioned above.

The blade 20 having taken its desired position, an orifice 40 is drilled, or is already pre-drilled, passing through the blade 20, for example in a laterally raised portion, as visible in Figures 1 and 2, possibly also passing through the male spherical zone 31 and the shaft 24, and a pin 41 is force-fitted into this orifice. Thus, the blade 20 and the shaft 24 are firmly secured together.

In this illustrated embodiment, the female spherical zone 33 is an area defined between two bases located on either side of its diametrical plane. But it is possible, according to another embodiment, for this female spherical zone 33 to have a structure whose diametrical plane is located outside the portion of space defined between these bases.

Furthermore, in the embodiment according to these figures 1 and 2, the male spherical zone 31 is produced according to a sphere consisting of an assembly of at least two parts, to be able to be more easily introduced into the female spherical zone 33.

It is however understandable that it is not easy to introduce and/or realize a male sphere in a portion of female sphere, as mentioned above to obtain an embodiment according to figures 1 and 2. The FIG. 4 illustrates a second embodiment of the cage according to the invention, which largely overcomes this problem.

This achievement according to the FIG. 4 is an application of the present invention, given as an example, with two blades 20, 20' on the same shaft 24, these two blades 20, 20' each defining an anchoring plane, these two planes forming between them, advantageously preferably a non-zero angle, as explained in FR2955483 mentioned above.

The means for connecting the blade 20' to the rotation shaft 24 have characteristics similar, if not identical, to those defined above for connecting the blade 20 to the shaft 24.

For the understanding of the structure according to the realization of the FIG. 4 , reference is made to the teaching of the FIG. 3 .

In this second embodiment, the male and female spherical zones 31, 33 each comprise at least one thread 51, 52 (of a relatively small width compared to that of the element 10). These two threads are substantially complementary to be able to cooperate with each other, the thread of the female spherical zone further bordering a hollow groove 53, preferably spherical substantially of the same radius as that of the male spherical zone 31 taken at the top of the thread 51, in which the thread 51 of the male spherical zone 31 is able to be positioned there.

For this, the width of the thread 51 of the male spherical zone 31 is advantageously less than the width of the groove 53.

In this way, when the thread 51 passes the thread 52, it falls into the groove 53. In this position, the female spherical zone 33 can move relative to the male spherical zone 31 according to at least two degrees of freedom.

The representation of the FIG. 3 shows, in part and in continuous lines, the male spherical zone 31 Zsm outside the female spherical zone 33 before the two threads 51, 52 cooperate with each other and, in broken lines, the male spherical zone 31 Zsm in the female spherical zone 33 after the thread 51 has passed the thread 52 and is positioned in the groove 53.

In this position, as illustrated in the FIG. 3 , the blade 20 can therefore pivot in the solid angle Ad and take the desired angular position relative to the axis 21.

It should be noted that, in this case, the two spherical zones male Zsm and female Zsf may have radii of different value, but this embodiment must be considered as included in the definition of the present invention.

In the mode of representation according to this FIG. 3 , the female spherical zone 33 can pivot in a solid angle Ad according to a relatively large amplitude in a plane parallel to that of the threads 51, 52 and of a smaller amplitude in a plane perpendicular to these two threads, this amplitude then being a function of the difference between the width of the groove 53 and the width of the thread 51.

It should be noted that, although, on the FIG. 4 , the blades 20, 20' are slightly distant from the wall of the element 10, they can be, in another embodiment, positioned very tightly, and even under pressure, against the wall of this element 10.

From the description given above, it is obvious, particularly to those skilled in the art, that the cage according to the present invention has numerous advantages over the cages of the prior art.

Claims (8)

Intervertebral cage capable of being interposed between two vertebral bodies to replace the intervertebral disc originally located between the two vertebrae, comprising: an element (10) having the general shape of a disc comprising two opposite faces (11, 12) substantially parallel and a lateral wall connecting said two opposite faces, these opposite faces being capable of coming into contact respectively with the two vertebral bodies and substantially defining two planes which contain them; at least one locking blade (20), the overall width of this blade, measured in the plane substantially perpendicular to the two opposite faces, being at most equal to the distance separating these two opposite faces and its overall length measured in this same plane being greater than this distance; means for rotating said blade (20) around an axis (21) so that this blade is able to take any position between a first position (P1) and a second position (P2), the first position (P1) being that in which the blade is entirely contained in the space defined between the planes of the two opposite faces (11, 12) and the second position (P2) being that in which at least one end (22) of the blade emerges from this space, these means for rotating the blade comprising a shaft (24) mounted to rotate relative to the element around said axis (21) and means for connecting the blade with said shaft (24), characterized in that the means for connecting the blade with said shaft comprise:
• a male spherical zone (31) produced in cooperation with said shaft (24), the radius of this male spherical zone having a determined value,
• a through-hole (32) made in said blade (20), the inner wall of which has the shape of a female spherical zone (33), the radius of this female spherical zone having a value at least equal to the value of the radius of the male spherical zone (31) so that said female spherical zone is able to pivot relative to said male spherical zone (31) according to a given central angle value (Ad), and
• means for securing said blade (20) with said shaft (24) in a given angular position relative to said axis of rotation (21). Cage according to claim 1, characterized in that said female spherical zone (33) has two bases. Cage according to claim 2, characterized in that the two bases are located on either side of the diametrical plane of said female spherical zone (33). Cage according to one of the preceding claims, characterized in that the means for securing said blade (20) with said shaft (24) in a given angular position relative to said axis of rotation (21) comprise an orifice (40) made in said blade and said shaft, optionally in said male spherical zone (31), and a pin (41) capable of being inserted into said orifice (40). Cage according to one of the preceding claims, characterized in that said male and female spherical zones (31, 32) each comprise at least one thread (51, 52), the two threads being substantially complementary and capable of cooperating with each other, the thread (52) of said female spherical zone bordering a hollow groove (53) in which the thread (51) of the male spherical zone (31) is capable of being positioned after having been screwed into the thread (52) of said female spherical zone (32). Cage according to one of the preceding claims, characterized in that said male spherical zone (31) consists of an assembly of at least two parts. Cage comprising at least one other blade (20') and other means for connecting said other blade (20') with said shaft (24), said other means meeting the characteristics as defined in at least one of the preceding claims. Cage according to claim 7, characterized in that the two blades (20, 20') each define an anchoring plane, these two planes forming a non-zero angle between them.