FR2955249A1 - MEDIAN INTERSOMATIC CAGE - Google Patents

Abstract

The invention relates to a medial intersomatic cage (1) having first and second side walls (2, 3) disposed on either side of at least one bone graft housing (4), said side walls (2, 3) being designed to form a contact surface adapted to two intersomatic cages (5, 6) when these are arranged on either side of said medial intersomatic cage (1). The invention also relates to a bone graft implant kit that includes a medial intersomatic cage (1).

Description

The present invention relates to the field of intersomatic cages which allow the implantation of a bone graft in an intervertebral space. The present invention is particularly intended to achieve the immobilization of the lumbar vertebrae, and this unilateral posterior route. The human spine forms the mobile axial skeleton of the body and serves above all to stabilize the head, bust and upright position. The vertebrae, which are bones with a particular morphology giving them a strong resistance against the pressures exerted up and down during movements (such as jumps, walking) ensure this stabilization. In addition, the vertebrae and the vertebral arches form a channel in which the spinal cord and the departure of the nerves are, which are thus protected from external aggressions. The intervertebral discs, inserted between the vertebrae, not only cushion the impact but also the vertebral joints perform the movements of rotation, extension and flexion. However, degenerative lesions of the spine often associated with natural aging, can occur and cause pathological changes in vertebral bodies, intervertebral discs, ligaments and intervertebral joints. These alterations then lead to greatly limit the mobility and stability of the spine; which can be a source of considerable pain, because the vertebral joints undergo inappropriate constraints. In particular, an intervertebral disc may collapse with aging, causing local compression of the spinal cord and nerve roots. To remedy this, it is possible to insert an implant between the trays of the two vertebrae concerned which will serve as a support for a bone graft, so as to restore the anatomical intervertebral space and to merge the two vertebrae by osteogenesis. As a result, the hitherto compressed nerves are released and the vertebral joints return to their physiological position. The spine thus recovers its normal dynamic function and the pain caused by this collapse of an intervertebral disc are relieved. The implant can consist of a rigid implant, also called "intersomatic cage", which is inserted between the vertebrae. It is open at its upper and lower ends and can be partitioned so as to delimit one or more bone graft housing, and this to allow the arrival of the graft in contact with the cancellous bone of the vertebral trays. In addition, such an intersomatic cage generally comprises a so-called "outer wall" wall, substantially curved so as to facilitate the sliding of the cage after its introduction between the vertebrae and a so-called "inner wall" wall substantially flat. It is known to juxtapose two intersomatic cages in the intervertebral space so that the walls called "internal walls" face each other. However, there are morphological variations from one individual to another, and therefore in particular in the morphology of the spine, because bone structure and bone quality (ie, bone porosity function) can vary; which implies that the implant of two intersomatic cages juxtaposed may be insufficient to address the aforementioned problems, because of their maladaptation to the morphology of the patient.

The present invention overcomes this disadvantage by providing a medial intersomatic cage which has first and second side walls disposed on either side of at least one bone graft housing, said side walls being designed to form a surface contact adapted to two intersomatic cages when they are disposed on either side of said medial intersomatic cage. Thus, thanks to this medial intersomatic cage according to the present invention, the surgeon can adapt precisely to the morphology of the patient by implanting this medial intersomatic cage between two intersomatic cages in an intervertebral space. Moreover, by the design of its side walls, the median intersomatic cage according to the invention can be arranged indifferently in both possible directions. Preferably, the side walls of the medial intersomatic cage according to the invention are planar. In one embodiment of the invention, the median intersomatic cage according to the invention has a length of about 23 mm, a width of 8.5 mm, and a height of between 8 and 15 mm, preferably of 9, 11 or 13 mm. Preferably, the median intersomatic cage is made of a radiolucent biocompatible material such as polyether ketone, carbon fiber or a mixture of these two materials. Very advantageously, the median intersomatic cage is made of polyether ketone. In a preferred embodiment of the invention, the medial intersomatic cage comprises means for fixing a cage holder.

Advantageously, the medial intersomatic cage according to the invention comprises at least two controls in a radiopaque material, such as tantalum, which are arranged so as to allow the post-operative control of the positioning of the cage, and in particular of check that the cage has not migrated.

Another object of the present invention is an implant kit intended to be implanted in an intervertebral space, in particular in an intervertebral space of lumbar vertebrae, said implant kit comprises two intersomatic cages and a median intersomatic cage according to the invention as described above. Advantageously, the cages of the kit according to the invention comprise a means of attachment to a cage holder. Preferably, the cages of the kit according to the invention are made of a radiolucent biocompatible material such as polyether ketone or carbon fiber or a mixture of these two materials. Very advantageously, polyether ketone is used.

In a preferred embodiment of the invention, at least one of the intersomatic cages and / or the medial intersomatic cage comprises an etching, preferably a mechanical etching. In one embodiment of the invention, the kit comprises: two intersomatic cages 23 mm long, 10 mm wide and 8 to 15 mm high, and a median intersomatic cage 23 cm long. mm, width 8.5 mm, and height ranging from 8 to 15 mm. Thus, the surgeon uses the kit according to the present invention for multiple patients with very varied morphologies. The latter therefore no longer needs to have intersomatic cages of different sizes to adapt to the morphology of the operated patient. For a good understanding, the invention is described below with reference to the figures which represent an embodiment of the present invention, without this constituting any limitation.

Figure 1a is a perspective view of a medial intersomatic cage according to the invention.

Figure 1b is a perspective view of a kit according to the invention. The medial intersomatic cage 1 shown in Figure la has a first side wall 2 and a second side wall 3 which are arranged on either side of two bone graft housing 4. These two side walls 2, 3 are substantially flat. Moreover, by the design of its side walls 2, 3, this medial intersomatic cage 1 can be arranged indifferently in both possible directions in an intervertebral space. Each side wall 2,3 has lumens 7 allowing blood circulation for osseointegration, once the medial intersomatic cage 1 has been implanted in the intervertebral space. The medial intersomatic cage 1 comprises two tantalum controls 8 (one of which is not visible in FIG. 1a), so that it can be verified by radiography that the medial intersomatic cage 1 once implanted in the patient does not have migrated.

The medial intersomatic cage 1 comprises a mechanical etching 9 making it possible to identify it with respect to other intersomatic cages. The medial intersomatic cage 1 is implanted in the intervertebral space unilaterally posteriorly by means of a cage holder (not shown in Figure 1a). To do this, the cage holder is designed so as: - to be able to be fixed to a fixing means 15 that comprises the median intersomatic cage 1, and to be able to be removed from this fixing means 15, since said cage medial intersomatic 1 is implanted correctly in the intervertebral space. In a preferred manner, the cage holder may consist of a rigid metal elongate rod of suitable dimensions for effecting the implantation of the medial intersomatic cage 1 in the intervertebral space. One of the ends of the rod is designed to attach to the fastening means 15. Advantageously, the fastening means 15 consists of a threaded hole. Furthermore, the medial intersomatic cage 1 according to the present invention has been sterilized by gamma rays. Figure lb is a perspective view of a kit 10 according to the invention.

The kit 10 comprises two intersomatic cages 5,6 and a median intersomatic cage 1. The interbody cages 5,6 and the medial intersomatic cage 1 of the kit 10 each comprise two housing 4 of bone graft, as well as lights 7 allowing the circulation of the blood for osteointegration once said intersomatic cages 5.6 and the medial intersomatic cage 1 are implanted in an intervertebral space of lumbar vertebrae. The intersomatic cages 5,6 and the medial intersomatic cage 1 of the kit 10 further comprise a fixing means 15, allowing a cage holder (not shown in Figure 1b) to be fixed. The cage carrier may be that as described above. Preferably, the fixing means 15 is a threaded hole. The medial intersomatic cage 1 has substantially plane lateral walls 2, 3 and which are designed to form a contact surface adapted respectively to the inner wall 11 of the intervertebral cage 6 and to the inner wall 12 of the intervertebral cage 5. The inner walls 11, 12 are also substantially flat. The outer wall 13 of the intersomatic cage 6 and the outer wall 14 of the intersomatic cage 5 are substantially curved so as to facilitate the sliding of said cages 5,6 after their introduction between the vertebrae. Thus, thanks to the kit 10 according to the invention, depending on the morphology of the patient, the surgeon may decide to implant in the intervertebral space the two intersomatic cages 5,6 and the medial intersomatic cage 1 of the kit 10. Or this last medial intersomatic cage 1 is not implanted in the intervertebral space. The surgeon adapts precisely to the morphology of the patient. Also, the two intersomatic cages 5, 6 and the medial intersomatic cage 1 can be substantially spaced from each other in this intervertebral space, which makes it possible to adjust better to the morphology of the patient. Finally, the surgeon can use the kit 10 according to the present invention for multiple patients with very varied morphologies. The latter therefore no longer needs to have intersomatic cages 5,6 of different sizes to adapt to the morphology of the operated patient. In addition, the intersomatic cages 5.6 and the medial intersomatic cage 1 of the kit 10 comprise an etching 9 making it possible to identify them. The mention "II" is engraved on the cage 1, and the mentions "1" and "III" are etched respectively on the interbody cage 6 and the intersomatic cage 5. Moreover, the interbody cages 5,6 and the medial intersomatic cage 1 of the kit 10 according to the invention have been sterilized by 5 gamma rays. Also, the intersomatic cages 5,6 and the medial intersomatic cage 1 of the kit 10 according to the invention comprise two tantalum controls 8 (only one of the two controls is shown in FIG. 1b), so as to be able to locate the positioning of the cages and verify that they have not migrated after implantation. Finally, thanks to the kit 10 according to the invention, the insertion of the medial intersomatic cage 1 according to the present invention between two intersomatic cages 5,6 allows the resulting implant to have the following advantages compared to an implant consisting of two interbody cages, as known from the state of the art: This implant is perfectly adapted to the morphology of the patient. • This implant has an increased bone graft area, and bone contact with the vertebrae between which it is implanted is maximized.

This implant has an increased number of bone bridges and thus increased contact area between bone graft and vertebral plateaus; this can be particularly advantageous when the bone porosity of the patient is important. • The stability of this implant is increased.

The implantation of this implant is performed unilaterally posteriorly; which is a less invasive surgical technique and therefore less dangerous than other techniques known from the state of the art.

Claims (10)

REVENDICATIONS1. Medial intersomatic cage (1) having first and second side walls (2,3) disposed on either side of at least one bone graft housing (4), said side walls (2,3) being constructed of so as to constitute a contact surface adapted to two intersomatic cages (5,6) when they are arranged on either side of said median intersomatic cage (1). 2. median intersomatic cage (1) according to claim 1, characterized in that said side walls (2,3) are flat. 3. median intersomatic cage (1) according to claim 1 or 2 characterized in that said medial intersomatic cage (1) is made of a radiolucent biocompatible material such as polyether ketone. 4. middle intersomatic cage (1) according to any one of claims 1 to 3 characterized in that said medial intersomatic cage (1) comprises a fixing means (15) to a cage holder. 5. median intersomatic cage (1) according to any one of claims 1 to 4 characterized in that said median intersomatic cage (1) comprises at least two controls (8) of a radiopaque material. 6. median intersomatic cage (1) according to any one of claims 1 to 5 characterized in that said median intersomatic cage (1) has a length of 23 mm, a width of 8.5 mm and a height of between 8 and 15 mm. Implant kit (10) intended to be implanted in an intervertebral space, in particular in an intervertebral space of lumbar vertebrae, which comprises two intersomatic cages (5, 6), characterized in that said kit (10) comprises in in addition to a medial intersomatic cage (1) according to any one of claims 1 to 6. 8. Kit (10) according to claim 7 characterized in that at least one of the intersomatic cages (5,6) and / or the medial intersomatic cage (1) comprises an etching (9), preferably a mechanical etching. 9. Kit (10) according to any one of claims 7 to 8 characterized in that the intersomatic cages (5,6) have a length of 23 mm, a width of 10 mm and a height of between 8 and 15 mm and the medial intersomatic cage (1) has a length of 23 mm, a width of 8.5 mm and a height of between 8 and 15 mm. 10. Kit (10) according to any one of claims 7 to 9 characterized in that the intersomatic cages (5,6) and the medial intersomatic cage (1) comprise a fixing means (15) to a cage holder. 15