FR2875697A1 - Intervertebral implant for treatment of cervical vertebras, has longitudinal median wall with lower and upper edges respectively having concave and convex forms, and peripheral wall with upper and lower edges having asperities - Google Patents

Abstract

The implant has a longitudinal median wall (4) with a lower edge (4b) having, in sagittal plane, a concave form and extending in retreat of a lower edge of a peripheral wall (2). The wall (4) includes an upper edge (4a) having, in sagittal plane, a convex form and projecting with respect to an upper edge of the wall (2). The upper and lower edges of the wall (2) are provided with a series of asperities (5). An independent claim is also included for a porous material block utilizable with an intervertebral implant.

Description

The present invention relates to an intervertebral implant, in particular for the

  treatment of cervical vertebrae.

  It is well known to insert a rigid implant, hollow internally, between two cervical vertebrae. Such an implant has the function of restoring the distance and the anatomical position of these vertebrae, and of making a relative immobilization of these vertebrae by growth of the bone cells through the implant.

  To make this growth possible, the implant comprises a peripheral wall delimiting an internal cavity for receiving a bone graft, natural or synthetic. The upper and lower openings of this cavity allow the graft to come into contact with the respective vertebral endplates in order to allow said growth of the bone cells through the graft.

  As regards treatment of cervical vertebrae, the implementation of the implant is done by anterior route.

  The existing intervertebral implants have the disadvantage of presenting difficulties of insertion between the vertebrae and the risk of expulsion under the effect of the repeated movements of the vertebrae. In addition, when the vertebral endplates have been started at the time of the development of the receiving housing of the implant, or the implants have limited bearing surfaces against these trays, the existing implants present risks of penetration into the implant housing. the bone of the vertebrae.

  In addition, the holding of a bone graft in the cavity of an implant is not always well ensured, which can hinder the establishment of the implant between the vertebrae.

  It also appears that the bone grafts used with existing implants do not always make it possible to obtain a vertebral fusion in perfect conditions.

  The present invention aims to remedy all of these disadvantages.

  The implant concerned comprises, as is known, a peripheral wall delimiting an internal cavity for receiving a graft.

  According to the invention, the implant comprises a median longitudinal wall whose lower edge, seen in the sagittal plane, is recessed and extends back from the lower edges of said peripheral wall.

  This median longitudinal wall substantially reinforces the structure of the implant while making it possible, thanks to its hollow bottom edge, the establishment of a monobloc graft in the cavity of the implant. This monobloc character of the graft allows the filling of this cavity in a single operation and above all allows a retention effect of this graft in the cavity. This retention effect results from the different bearing surfaces that said median longitudinal wall allows to develop in the implant. The establishment of an implant is greatly facilitated.

  The reinforcement of the abovementioned implant makes it possible to use specific materials for producing this implant, in particular polyaryletheretherketone, a material known by the abbreviation "PEEK".

  The implant according to the invention and in particular intended to receive a block of porous material colonizable by the growing bone cells; this block of material has pores oriented in the same direction and is shaped according to the shape of the cavity of the implant so that, once put in place in this cavity, its pores are oriented in a direction parallel to the lateral faces of said middle longitudinal wall. The specific shape of the cavity, divided into two lateral portions connected by an intermediate zone, involves placing the block of material in a single position of this block in this cavity, in which the pores of the blocks of material are orientated the most favorable for the growth of bone cells from one vertebra towards the other vertebra and thus to ensure a perfect fusion of these two vertebrae.

  The risk of defective placement of the graft is eliminated.

  The fusion with the underlying vertebra is also achieved in very good conditions because of the large contact area of the graft with it.

  Preferably, the upper edge of said median longitudinal wall has, seen in a sagittal plane, a convex shape and protrudes with respect to the upper edges of said peripheral wall.

  This convex upper edge provides the overlying vertebra an increased bearing surface on the implant and reduces the risk of insertion of the implant in this vertebra accordingly. This upper edge also has a shape adapted to the more or less concave shape of the vertebral plateau of the overlying vertebra.

  The lower edge of said middle longitudinal wall is preferably concave. It may or may not have a curvature corresponding to that of the convex upper edge.

  Preferably, the above convex upper edge has a series of asperities adapted to penetrate the overlying vertebral plateau or spongy bone of the overlying vertebra.

  Increased retention of the implant is thus made possible particularly when these asperities have a sawtooth profile with vertical faces oriented on the anterior side of the implant.

  Said middle longitudinal wall may have a constant thickness or advantageously have, in its anterior half, an enlarged shape.

  This enlarged shape further strengthens the implant structure and increases the area that can be occupied by said bearing asperities against the overlying vertebral plateau.

  According to a preferred embodiment of the invention, in this case, the anterior half of said longitudinal wall gradually increases in thickness in the direction of the anterior part of the implant and has a thickness varying substantially from the single to the double of one end. to the other of this previous half.

  The upper and / or lower edges of said peripheral wall of the implant advantageously comprise asperities for taking hold against the vertebral plate or plates.

  Preferably, these asperities have, like that of said upper convex edge, a sawtooth profile with vertical faces oriented on the anterior side of the implant.

  In addition, advantageously, the implant comprises at least one anchoring pin protruding from at least one of its upper and lower faces, adapted to penetrate into the vertebral plateau of the corresponding vertebra to ensure the immobilization of the implant. between the vertebrae.

  In the preferred embodiment of the implant according to the invention, this implant comprises three pyramidal-shaped pins protruding from its lower face, arranged in a triangle, one of these pins being located in the posterior medial zone of the implant. implant and the two other pins being located in the anterolateral areas of this implant.

  The invention will be better understood, and other features and advantages thereof will become apparent, with reference to the appended schematic drawing, showing, by way of non-limiting example, a preferred embodiment of the implant that it relates. .

  Figures 1 to 3 are perspective views, from three different angles; Figure 4 is a view from below; Figure 5 is an end view, anterior side, and Figure 6 is a side view.

  The figures show an intervertebral implant 1 intended to be inserted between two vertebrae, in particular cervical vertebrae, to restore the distance and the anatomical position of these vertebrae, and to operate a relative immobilization of these vertebrae by growth of the bone cells through it.

  The implant 1 comprises a peripheral wall 2 delimiting an internal cavity 3 for receiving a bone graft (not shown), and a median longitudinal wall 4.

  As shown in FIGS. 3 and 4, the anterior half (with respect to the treated vertebrae) of the wall 4 progressively increases in thickness in the direction of the anterior part of the implant 1 and has a thickness that varies substantially from one to two times one end to the other of this anterior half.

  The upper edge 4a of the wall 4 has, seen in a sagittal plane (see FIG. 6), a convex shape and protrudes with respect to the upper edge of said peripheral wall 2. It comprises a series of asperities 5 with an internal profile. sawtooth, having vertical faces oriented on the anterior side of the implant 1.

  The upper and lower edges of the peripheral wall 2 also comprise series of asperities 5, also having a sawtooth profile, of the same orientations as those of the edge 4a. These asperities 5 are able to penetrate slightly into the vertebral endplates of the treated vertebrae.

  The median longitudinal wall 4 further has a lower edge 4b having, seen in the sagittal plane, a concave shape and extending back from the lower edges of the peripheral wall 2. In the example shown, the curvature of this edge 4b corresponds substantially to that of the edge 4a.

  The edge 4b may be smooth as shown in Figures 1, 2 or 6, or may have similar asperities to the edge 4a, as shown in Figures 3 and 4.

  The implant 1 also comprises three pins 6 of pyramidal shape, projecting from its lower face, arranged in a triangle. One of these pins 6 is located in the posterior median zone of the implant 1 and the two other pins 6 are located in the anterolateral areas of this implant.

  In addition, the anterior wall of the implant comprises a hole 7 and recesses 8 for mounting the implant 1 on an impaction instrument.

  In practice, a suitable housing is arranged through the intervertebral disc and, where appropriate, in the vertebral endplates. The vertebrae are then distracted and the implant 1 is put in place by means of said instrument.

  The median longitudinal wall 4 substantially reinforces the structure of the implant 1 while making it possible, thanks to its lower edge 4b, the introduction of a monobloc graft in the cavity 3. This monobloc character of the graft allows the filling of this cavity 3 in a single operation and above all allows a retention effect of this graft in the cavity 3.

  This retention effect results from the different bearing surfaces that the wall 4 allows to fit into the implant 1. The establishment of an implant is greatly facilitated.

  Strengthening the implant allows the use of specific materials to achieve this implant, including "PEEK" (polyaryletheretherketone).

  The use of the implant 1 is particularly advantageous when the graft comprises pores oriented in the same direction. The specific shape of the cavity 3, divided into two lateral portions connected by an intermediate zone, involves the introduction of a graft of specific shape corresponding to that of the cavity 3, and thus makes it possible to define a single positioning of this graft in this cavity. The graft is arranged such that, when it is placed in the cavity 3, its pores are oriented parallel to the lateral faces of the wall 4, this orientation being the most favorable for the growth of bone cells of a vertebra towards the other vertebra and to ensure a perfect fusion of these two vertebrae. The risk of defective placement of the graft is eliminated.

  The fusion with the underlying vertebra is also achieved in very good conditions because of the large contact area of the graft with it.

  It goes without saying that the invention is not limited to the embodiment described above by way of example but that it extends to all embodiments covered by the appended claims.

Claims (9)

  1 intervertebral implant (1) in particular for the treatment of cervical vertebrae, comprising a peripheral wall (2) delimiting an inner cavity (3) for receiving a graft, characterized in that it comprises a median longitudinal wall (4), the lower edge (4b), seen in the sagittal plane, is recessed and extends back from the lower edges of said peripheral wall (2).   2 intervertebral implant (1) according to claim 1, characterized in that the upper edge (4a) of said median longitudinal wall (4) has, seen in a sagittal plane, a convex shape and protrudes from the upper edges of said peripheral wall (2).   3 intervertebral implant (1) according to claim 1 or claim 2, characterized in that the lower edge (4b) of said median longitudinal wall (4) is concave.   4 intervertebral implant (1) according to claim 3, characterized in that the lower edge (4b) of said median longitudinal wall (4) has a curvature corresponding to that of the convex upper edge.     Intervertebral implant (1) according to one of claims 1 to 4, characterized in that the convex upper edge (4a) has a series of asperities (5) suitable for penetrating the overlying vertebral plateau or the bone spongy of the overlying vertebra.   6 intervertebral implant (1) according to one of claims 1 to 5, characterized in that said longitudinal wall (4) has substantially in its anterior half, an enlarged shape.   7 intervertebral implant (1) according to claim 6, characterized in that the anterior half (4b) of said longitudinal wall (4) gradually increases in thickness towards the front part of the implant (1) and has a varying thickness substantially from single to double from one end to the other of this front half (4b).   8 intervertebral implant (1) according to one of claims 1 to 7, characterized in that the upper and / or lower edges of said peripheral wall (2) comprise asperities (5) of support against the or trays vertebral.   9 intervertebral implant (1) according to one of claims 5 to 8, characterized in that the asperities (5) of the convex upper edge (4a) and / or those of said peripheral wall (2) have a sawtooth profile with vertical faces oriented on the anterior side of the implant.   Block of porous material intended to be colonized by the growing bone cells, usable with the implant (1) according to one of claims 1 to 9, characterized in that it has pores oriented in the same direction and in that it is shaped according to the shape of the cavity (3) of the implant (1) so that, once put in place in this cavity (3), its pores are oriented in a direction parallel to the lateral faces of said middle longitudinal wall (4).