FR2801783A1 - Inter-vertebral cage for spinal surgery has parallelepiped body with bore receiving bone graft and stop plate to retain graft under pre-load - Google Patents

Abstract

The inter-vertebral cage for spinal surgery has a rectangular body (10) with two side faces to contact adjacent vertebrae (2,3). The body has a transverse bore (19) and a longitudinal bore (16). A stop plate (30) is mounted in the longitudinal bore (16) so that when a bone graft is placed into the bore it is subjected to an axial pre-load.

Description

The present invention relates to intersomatic cages which are used to suppress the cause of pain generated by a damaged intervertebral disc.

An intersomatic cage is a prosthetic device adapted to be implanted between two vertebrae for the purpose of replacing a damaged intervertebral disk to form, as it were, at first a spacer between the two vertebrae, and secondly a means for promoting osteosynthesis between these two vertebrae so that they can no longer move relative to each other.

Such intersomatic cages are already known, for example those described and illustrated in the documents US-A-4,501,269, WO-A-89 12431 and EP-A-0 307 241.

In general, they consist of an oblong body whose outer shape allows them to be inserted between two vertebrae by anchoring and comprise a central housing made in the oblong body. This accommodation is put in communication. through holes made in the body wall, with the external faces of the cage which are intended to come into contact with the two vertebrae and is shaped to contain a bone graft so that the graft can grow there and achieve a bone connection between the two vertebrae to definitively bind them by osteosynthesis.

The structure of these intersomatic cages of the prior art is, however, rather adapted to the spacer function and does not make it possible to obtain optimum contact between the bone graft and the two vertebrae so as to join these two vertebrae together by osteosynthesis. as quickly and efficiently as possible.

The object of the present invention is thus to provide an intersomatic cage capable of being implanted between two vertebrae, the structure of which favors the positioning of the bone graft and the realization of the bone connection between these two vertebrae.

More specifically, the subject of the present invention is an intersomatic cage capable of being implanted between two consecutive vertebrae, comprising: an oblong body defined on a longitudinal axis and delimited by two end faces and at least two opposite lateral faces, the latter being adapted to take contact respectively with the two vertebrae, - a longitudinal through-hole formed in said elongated body substantially along said longitudinal axis and opening on both end faces by two openings, said pierced being shaped to receive a bone graft, - to at least one through orifice formed in the elongate body along a transverse axis substantially perpendicular to said longitudinal axis, said orifice opening into the longitudinal through-hole and on one of the two lateral faces, characterized in that it further comprises a mounted stopper; in cooperation with the longitudinally traversing rim so that, when said bone graft is inserted into said longitudinal through-bore and is subjected to a pressing force substantially along the longitudinal axis, said stopper exerts on the bone graft a reaction force constraining it to to deform to partially penetrate into said through hole and partly to partially exceed the stop.

Other characteristics and advantages of the invention will emerge in the course of the following description given with reference to the accompanying drawings for illustrative but not limiting purposes, in which FIG. 1 represents the block diagram of an embodiment of a cage FIGS. 2 and 3 show, respectively in cross-section and end view, an embodiment of an intersomatic cage in accordance with the schematic representation of FIG. 1, the section according to FIG. 2 being referenced 11 11 in FIG. 3 and the end view according to FIG. 3 being that indicated by the arrow "F" in FIG. 2; FIG. 4 represents a diagram making it possible to explain an advantageous form of the intersomatic cage according to the invention; facilitating its placement between two vertebrae, this embodiment being in accordance with the embodiments shown in Figures I to 3, and Figures 5 and 6 represent t two diagrams highlighting the advantage of the shape of the intervertebral cage according to the embodiment of Figure 4, when placed between two vertebrae.

Figures 1 to 6 show three embodiments of the device according to the invention. However, the same references designate the same elements, whatever the figure on which they appear and whatever the form of representation of these elements.

FIG. 1 represents the basic diagram of an interbody cage 1 according to the invention that can be implanted between two consecutive vertebrae 2, 3.

It comprises an oblong body 10 made of a material such as titanium or the like. This elongated body 10 is defined along a longitudinal axis 1 1 and delimited by two end faces 12, 13 and at least two opposite lateral faces 14, 15 able to respectively contact the two vertebrae 2, 3. In this oblong body 10, is made a longitudinal through-hole 16 substantially along the longitudinal axis 11 defined above. It opens on both end faces 12, 13 by two openings 17, 18 and is shaped to receive a bone graft 20.

In addition, at least one through hole 19 is provided in the wall of the elongated body along a transverse axis 21 substantially perpendicular to the longitudinal axis <B> 11, </ B> this orifice opening into the longitudinal through-hole 16 and one of the two lateral faces 14, 15. Advantageously, such a cage comprises, as illustrated in Figure 1, at least two through holes 19 made in the elongated body 10 along two transverse axes 21 substantially coincident and perpendicular to the axis longitudinal 11, these two openings opening on the one hand in the longitudinal through-hole 16 and on the other hand respectively on the two lateral faces 14, 15.

According to an important characteristic of the invention, the cage further comprises a stop 30 mounted in cooperation with the longitudinal through-breakthrough 16 so that, when the bone graft 20 is introduced into this longitudinal through-hole and is subjected to pressure force 40 substantially along the longitudinal axis 11, for example by means of a pusher as schematically illustrated in Figure 1. this retainer 30 exerts on the bone graft 20 a reaction force forcing it to deform to, d ' one part partially penetrate into the through hole 19 (or the two through-holes as previously stipulated) and partly beyond the stop 30.

The retainer may be disposed at any point of the throughthrough. However, advantageously, it is mounted in cooperation with this through hole so that, as illustrated in Figure 1, this retainer 30 and the through hole 19 are located on either side of a substantially perpendicular plane 41 to the longitudinal axis 11 and substantially tangential to this through hole 19. It may even be substantially defined in this plane 41.

As illustrated in Figures 2 and 3, the retainer advantageously has the shape of a cross 31 partially blocking the longitudinal through-hole 16. It can even affect the shape of a grid which is equivalent to a plurality of crosses.

To be able to mount this stopper more easily in cooperation with the through-hole, it is advantageously secured for example by a ring 32 or the like, and the cage furthermore comprises means 33 for clipping the ring 32 on the wall 34 of the breakthrough therethrough. The implantation of such a cage, especially in the human body. is very delicate and it is generally possible to introduce the bone graft only by one of the two openings 17, 18, in this case the opening 17 in the case of Figures 1 to 3. Accordingly and so Advantageously, the stop 30 is located substantially in the plane of the other opening 18, 17, in this case the opening 18 in the case of FIGS.

Of course, the cage preferably comprises means 50, such as pins or the like, for anchoring the elongated body 10 in a bone portion of at least one of the two vertebrae 2, 3, and advantageously of the two vertebrae as illustrated. in Figures 2 and 3.

The elongated body and the pins can be made of any material. However, the body is advantageously made of a plastic material optionally comprising reinforcing elements, for example carbon fibers or the like, and in this case the pins are preferably made of a radiopaque material.

The intervertebral cage 1 described above with reference to FIGS. 1 to 3 is used in the following manner. It is first assumed that it has been implanted between two vertebrae 2 and 3 in a manner known to a practitioner. This practitioner then introduces the bone graft 20 into the through-hole 16, for example through the opening 17.

With a pusher, the practitioner exercises on this bone graft a pressure force. The graft is first pressed against the retainer 30, then deforms and, by creep, partially enters the two orifices 19 facing each other, arrows 42, (or the four orifices in the case of the embodiment according to Figure 2) until coming into close contact with a portion of the bone wall of the two vertebrae 2, 3, Figure 1. thereby ensuring a first bone connection.

But in addition, since the stop 30 does not block the entire through hole 16, under the action of the pressure force exerted on the bone graft, the latter can also deform to exceed this stop 30 to overflow of the breakthrough 16 out of the opening 18, arrows 43, and come along the end face 13 in close contact with. another part of the bone wall of the two vertebrae 2, 3, thereby ensuring another bone connection.

The intersomatic cage described above has a structure that allows to quickly and reliably achieve three bone connections between two vertebrae between which it has been implanted.

The first bone connection is that which is made through the orifices 19 facing each other. The second bone connection is that which is made along the end face 13 having the opening 18 to which is associated the retainer 30. Opposite the opening 17 by which the bone graft was introduced into the breakthrough 16 .

Finally, the third bone bond is that which is obtained along the end face <B> 1 </ B> 2 having the opening 17 through which the graft is introduced. Indeed, when the first two bone connections have been made, the through-hole 16 is filled with a complementary amount of bone graft sufficient to overflow the opening 17 and provide the bone connection along the end face 12.

Incidentally, as shown in broken lines in FIG. 2, the elongated body 10 may have other through orifices in the side wall portion, so that the graft may also overflow on each side of the cage to further promote the osteosynthesis.

FIGS. 4 to 6 show another advantageous embodiment of a cage according to the invention, in which the elongate body 10 has a substantially double-corner general shape, as schematically represented in FIG. 4.

This form of double-corner is substantially defined by the common part to a frustoconical volume of revolution and a dihedral so that this double-wedge has two bases which correspond to the end faces 12, 13 defined above with respect to the figures 1 to 3, the length and the width of one 12 of the two bases being respectively smaller and greater than the length and the width of the other base 13.

This form is particularly advantageous for laying the cage between two vertebrae, the two main phases of which have been very schematically represented in FIGS. 5 and 6.

It is first necessary to remember that an intersomatic cage is intended to be inserted between two vertebrae when the intervertebral disc is damaged and that there has been a tilting of one vertebra with respect to the other defining between them. two vertebrae a dihedral space.

Given this deformation, the practitioner can introduce the interbody cage as illustrated in Figure 4, between the two vertebrae so that, as shown schematically in Figure 5, the two end faces 12, 13 of the elongated body 10 have their length substantially parallel to the opposite faces of the two vertebrae 2, 3. In this configuration, the orifices 19 opening on the side faces 14, 15 of the elongated body are not facing the vertebrae.

After inserting the cage in this position, the practitioner subjects the elongate body 10 to a rotation of ninety degrees so as to bring the orifices 19 opposite the vertebrae 2, 3. In this rotation, the lengths of the two bases which was substantially parallel to the faces opposite the two vertebrae become substantially perpendicular to these two faces and the elongate body thus lever between the two vertebrae to restore their original relative position before the deterioration of the intervertebral disc.

Of course, the practitioner will introduce the oblong body by one or the other of its ends, according to the configuration of the pinching of the disc, and may then introduce, as described above, the bone graft or grafts to obtain osteosynthesis between the two vertebrae.

The oblong body shape defined above with reference to FIG. 4 is a general shape, this oblong body possibly having, for example, substantially cut-off faces at the end faces 12, 13 so that it can best fit the morphology of the vertebrae.

The description made above highlights the essential advantage presented by an interbody cage according to the invention, compared to prior intcrsomatic cages, namely the fact that, with a very simple structure, it allows the bone graft to constitute very well. quickly and reliably, three bone bridges between the two vertebrae between which it was implanted.

Claims (11)

1. Intersomatic cage (1) adapted to be implanted between two consecutive vertebrae (2, 3), comprising - an oblong body (10) defined on a longitudinal axis (11) and delimited by two end faces (12, 13) and at least two opposite lateral faces (14, 15), the latter being able to respectively contact the two vertebrae (2, 3), - a longitudinal through-hole (16) formed in said elongate body substantially along said longitudinal axis ( 11) and opening on both end faces (12, 13) by two openings (17, 18), said piercing being shaped to receive a bone graft (20), - at least one through hole (19) formed in the oblong body along a transverse axis (21) substantially perpendicular to said longitudinal axis (11), said orifice opening into the longitudinal through-hole (16) and on one of the two lateral faces (14, 15), characterized in that it has o a stopper (30) mounted in cooperation with said longitudinal through-bore (16) so that when said bone graft (20) is introduced into said longitudinal through-bore (16) and is subjected to a pressing force ( 40) substantially along the longitudinal axis (11), said retainer (30) exerts on the bone graft (20) a reaction force forcing it to deform to partially penetrate into said through hole (19) and on the other hand partially exceed the stop (30). 2. intersomatic cage according to claim 1, characterized in that said retainer (30) is mounted in cooperation with the longitudinal through-hole (16) so that said retainer (30) and said through hole (19) are located from and other of a plane (41) substantially perpendicular to said longitudinal axis (11) and substantially tangent to said through orifice (19). 3. intersomatic cage according to claim 2, characterized in that said retainer (30) is substantially defined in said plane (41). 4. intersomatic cage according to one of claims 1 to 3. characterized in that said retainer (30) has the shape of a cross (31) partially blocking the longitudinal through-hole (16). 5. intersomatic cage according to one of claims 1 to 3, characterized in that said retainer (30) has the shape of a gate partially blocking the longitudinal through-hole (16). 6. intersomatic cage according to one of claims 1 to 5, characterized in that said retainer (30) is integral with a ring (32), and it further comprises means (33) for clipping said ring (32) on the wall (34) of the longitudinal through-hole (16). 7. intersomatic cage according to one of the preceding claims, characterized in that it comprises at least two through holes (19) formed in the elongate body (10) along two transverse axes (21) substantially coincidental and perpendicular to said longitudinal axis (<B> 11 </ B>), said orifices opening into the longitudinal through-hole (16) and respectively on the two lateral faces (14, 15). 8. intersomatic cage according to one of the preceding claims, characterized in that it comprises means (50) for anchoring said body <U> oblong </ U> (10) in a bone part of at least the one of the two vertebrae (2, 3). 9. Cage according to claim 8, characterized in that the means (50) for anchoring the elongate body are constituted by pins, said elongate body (10) being made of a plastic material and the pins in a radiopaque material . 10. intersomatic cage according to one of claims 1 to 9, characterized in that said retainer (30) is located substantially in the plane of one of the two openings (17, 18). 11. Intersomatic cage according to one of claims 1 to 10, characterized in that said elongate body (10) has a substantially double-wedge shape (FIG 4), this form of double-wedge being substantially defined by the common part to a frustoconical volume of revolution and a dihedral so that this double-wedge has two bases (12, 13), the length and width of one (12) of the two bases being respcctively smaller and larger than the length and width of the other base (13).