FR2718955A1 - Intersomatic cage for fusion of lumbar vertebrae - Google Patents

Abstract

The intersomatic cage (2) has an octagonal cross-section and a vertical aperture (2a) through it, open in the cage's upper and lower faces (2b,2c), designed to receive a graft (3). The upper and lower faces of the cage are inclined to give it a tapering cross-section, and the vertical parallel side faces (2f,2g) are connected to the upper and lower faces by inclined faces (2h). The cage's end faces (2d,2e) are vertical and parallel, they are of the same width but different heights. The cage can be made from an inert metal such as titanium or from resorbable lactic acid polymer.

Description

1 2718955

  The present invention relates to an inter-somatic cage intended for

  The fusion of the lumbar vertebrae of a spine.

  Cages of this kind are known which generally have the shape of a hollow cylinder closed at each end, by means of a pointed profile and a threaded plug. The outer face of the cage has a series of oblong openings opening into the interior of the hollow cylinder. The cage is designed to receive pieces of grafts which come into contact through the oblong lights with the

  spongy part of the bone of the vertebrae to be fixed.

  It is found that this kind of cage with circular section has a small contact surface of the grafts with the cancellous bone of the vertebrae

  not allowing a perfect fusion of these. In addition, the chi-

  rurgien must perfectly position the cage in the housing before-

  duly realized between the vertebrae so that the oblong lights are

  found opposite the spongy part of the bone of the latter.

  It is to these drawbacks that more particularly intends to remedy

the present invention.

  The purpose of the inter-somatic cage according to the present invention is to considerably increase the surface of the graft in contact with the cancellous bone of each of the vertebrae while having good resistance.

mechanical crushing.

  The inter-somatic cage has in section an octagonal shape, the internal part of which is crossed vertically by a parallelepipedal recess opening on the upper and lower faces of

said cage.

  The appended drawing, given by way of example, will allow a better understanding of the invention, the characteristics which it presents and the advantages which it is capable of providing:

  Fig. 1 is a side view showing part of the vertices

  lumbar bres of the spine between which are arranged

  the inter-somatic cages according to the invention.

  Fig. 2 is a front view showing the arrangement of the cages with respect to each other between the lumbar vertebrae of a spine.

  Fig. 3 is a perspective view illustrating the inter-

  somatic according to the present invention.

  Fig. 4 is a section showing the profile of the hole made between

  the two vertebrae to be fused before the placement of the inter-cage

  somatic. Fig. 5 is a section showing the position of an inter-somatic cage after it has been placed between the two lumbar vertebrae.

  There is shown in fig. 1 and 2 the lower part of a green column

  1 of which the lumbar vertebrae are joined together by the

  diary of two identical inter-somatic cages 2.

  The inter-somatic cages 2 are introduced between the vertebrae la by the posterior route of the vertebral column 1 according to the arrow F1, that is to say on the side of the thorns 1b. The inter-somatic cages 2 are put in place after the partial removal of the inter-vertebral disc

  1c, as we will see better below.

  In fig. 3, an inter-somatic cage 2 has been shown having an octagonal profile and the internal part of which is pierced by a vertical recess 2a of substantially paralelepipedic shape. The recess 2a

  opens on the side of the upper 2b and lower 2c faces of the cage 2.

  The latter is provided along its slightly conical longitudinal axis, so that the upper 2b and lower 2c faces are inclined relative to each other, that is to say that they do not

  not found in two parallel planes.

  The conicity of the cage 2 makes it possible to define parallel vertical walls 2d and 2e of different heights, while their width is identical. Indeed, the vertical faces 2f and 29 perpendicular to the walls 2d and 2e are provided parallel to each other in different planes. The faces 2b and 2c are respectively connected to the vertical faces

  2f and 29 by 2h cut sections which are inclined at an angle of 45.

  The advantageous shape of the inter-somatic cage 2, that is to say its conical octagonal profile, makes it possible to obtain a solid monobloc graft 3 having a profile identical to that of the recess 2a. Edges

  upper 3a and lower 3b of graft 3 are provided to come respec-

  tif flush with the edge of the upper 2b and lower 2c faces of the cage 2. Thus, the edges 3a and 3b are provided inclined at the same angle as that of the faces 2b and 2c of the cage 2, while the vertical edges 3c and 3d are respectively parallel to those of faces 2f and 29. Also, the opposite edges 3e and 3f are parallel one to

  the other and perpendicular to edges 3c and 3d.

  The grafts 3 to be introduced into the cages 2 are made of a material consisting of cancellous bone originating either from the patient (autograft) or from another individual (allograft). Also, grafts 3 can be made from divided materials such as synthetic or similar substitutes, shaped before their

  respective introduction in Les évidements 2a.

  In fig. 4, a section of the vertebrae 1a and of the disc lc of the vertebral column 1 has been shown, in which a cutout 4 is produced having a profile identical to that of the cage 2. Each vertebra 1a is constituted in its central part of cancellous bone ld covered on its periphery with cortical bone. The cortical bone comprises it near the disc 1c of the cartilage fibers ensuring it a hard structure and

resistant.

  Before cutting 4, the surgeon removes partial-

  the lc disk. The shape of the cutout 4 makes it possible to Release on each

  one of the vertebrae on the one hand a large surface of cancellous bone ld which will come into contact with the graft 3 and on the other hand inclined sections of cortical bone allowing it to constitute support zones

  for the inter-somatic cage 2 in the hard and resistant part.

  In addition, the cutout 4 has a conical profile identical to that of the cage 2 along the depth of the vertebrae 11. The cut 4 is made so that the narrower base of the cone, that is to say that corresponding to the vertical wall 2d of the cage 2 is provided at the edge of the vertebrae, while the wider base is found at

  inside these and near the remaining lc disc.

  The surgeon then proceeds to the separation of the vertebrae a posteriorly (F1) to allow access to the cages 2 inside the cutout 4. Once the cages 2 introduced into the cutout 4, the surgeon removes the spacers and we see that said cages are

  trapped between the vertebrae due to their taper and the

cutting wire 4.

  In fig. 5, an inter-somatic cage 2 has been shown trapped between two vertebrae la and inside which is previously

introduces plugin 3.

  It is found that the latter is largely in contact with the bone spon-

  gieux lb of each of the vertebrae to facilitate the subsequent fusion of said vertebrae. The 2h cut sides of cage 2 come to rest against the hard and resistant cortical bone of each vertebra

  allowing good mechanical resistance of the assembly.

  The material of the cage 2 can be inert, that is to say metallic, for example made of titanium or else absorbable, for example made of polymer

lactic acid.

  It should also be understood that the above description has

  given as an example and does not limit the area

  ne of the invention which we would not leave by replacing the details

  of execution described by all other equivalents.

Claims (8)

CLAIMS R E V E N D I C A T I O N S   1. Inter-somatic cage intended for the subsequent fusion of the vertebrae   bres lumbar vertebral column, characterized in that it has in section an octagonal shape whose internal part is crossed vertically by a recess (2a) in which is introduced a graft (3), said recess opening on the upper faces ( 2b)   and lower (2c) of said cage (2).   2. Cage according to claim 1, characterized in that the upper (2b) and lower (2c) faces are inclined along the axis.   longitudinal of the cage (2) so that it has a conical profile.   3. Cage according to claim 2, characterized in that it comprises parallel vertical faces (2f and 2G) which are connected to   upper (2b) and lower (2c) sides by cut sides (2h).   4. Cage according to claim 3, characterized in that it comprises vertical walls (2d and 2e) perpendicular to the vertical faces (2f and 2G) and which are provided with the same width but with a different height.   5. Cage according to claim 1, characterized in that the graft-   fon (3) has the same geometric shape as the recess (2a) made in inside the cage (2).   6. Cage according to claim 3, characterized in that the sides   cut (2h) are tilted at an angle of 45.   7. Cage according to claim 1, characterized in that it is   made of an inert material such as metal or titanium.   8. Cage according to claim 1, characterized in that it is   made of an absorbable lactic acid polymer.