ZA200200791B

ZA200200791B - Interbody spinal stabilisation cage.

Info

Publication number: ZA200200791B
Application number: ZA200200791A
Authority: ZA
Inventors: Ciaran Bolger; John Bolger
Original assignee: Spinevision Sa
Priority date: 1999-07-01
Filing date: 2002-01-29
Publication date: 2003-03-26
Also published as: EP1278486B1; ATE291399T1; BR0011965A; KR100673143B1; MXPA02000178A; RU2258488C2; WO2001001894A1; JP4189151B2; IL147400A; EP1278486A1; CA2373788C; AU6165200A; CA2373788A1; DE60018988T2; JP2003503155A; IL147400A0; KR20020033648A; FR2795627A1; DE60018988D1

Abstract

The invention concerns an interbody spinal stabilisation cage comprising a hollow central space (4) designed to be filled with bone fragments. The invention is characterised in that it comprises anchoring means (3) emerging on side surfaces (5, 5') linking it with the adjacent vertebrae, driven by at least driving means (2) emerging of a front surface (6), said anchoring means (3) comprising each at least a main knife edge (10).

Description

1) hd 1 ES SET

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INTERBODY SPINAL STABILISATION CAGE

The present invention relates to the field of spinal orthopaedics, and more particularly to that of interbody cages.

Such prostheses are intended to stabilise pathological spinal segments and induce bone consolidation by means of the fusion of the two segments.

These cages are generally made from titanium, carbon or biocompatible composite material and receive bone grafts.

For example, it is possible to refer to the French patent application FR 2764795 disclosing an interbody cage according to the prior art. This cage comprises a central hollow space intended to be filled with bone fragments. It comprises, on its transverse section, two wide, convex faces, each equipped with a central opening, two narrow faces each equipped with a central opening, said narrow faces comprising slanting toothing distributed at either end of the central opening of the narrow faces. It also comprises a convex closed front end and a rear end comprising at its centre a polygonal housing to receive an adjustment device. A fitting key equipped with a polygonal fitting and a threaded rod co- operates with the cage according to the invention to insert it by means of impaction between the vertebrae and stabilise it by means of rotation after impaction..

Another French patent application published under the number FR2761879 discloses an implant which comprises, on 1ts two diametrically opposite sides intended to come into contact with the spongy bone of the vertebrae after implantation, a plurality of separate

AMENDED SHEET openings, offset at an angle with reference to the others by an interval corresponding roughly to half the length : of an opening, such that one of these openings is located opposite the part of the wall of the implant which separates two longitudinally adjacent openings.

Another patent application FR2717068 discloses an interbody cage to be inserted frontally between two vertebrae comprising two roughly parallel branches to come into contact with the vertebral bodies, a bridge connecting the rear ends of the branches after insertion of the cage between the two vertebrae. The cage enables preoperative setting of the lordosis angle between the two vertebrae. A cage holder is connected in a detachable manner to the cage to insert the cage between the two vertebrae. After the removal of the cage holder, a screwdriver turns a screw wherein the rear end is attached to the distance piece and screwed into one of the branches to separate the two cage branches.

It was also proposed in the American patent

No. US 5,800,550 to produce an interbody cage comprising toothed cylinders which can be pushed vertically into the vertebrae, by means of a tool equipped with a screw thread, in order to hold the interbody cage in place.

It was also proposed in the German patent application No. DE 4327054 to produce an interbody cage comprising a cam shaft used to raise support eye-bolts.

It was also proposed in the international patent application No. WO 97/06753 to produce an interbody cage comprising a more or less cylindrical hollow body 1, 51 equipped with one or more openings 9, 10, 59, 59', 60, 60'. The hollow body 1, 51 may be broadened in an adjustable manner by adjustment components 18, 19, 65, 66

AMENDED SHEET vf

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3 AS and comprises fixation components 24, 25, 69, 70, 71, 72 used to fix it on vertebrae.

It was also proposed in the international patent application No. WO 97/46165 to produce an interbody cage comprising at least two basic screws 1, two locking parts 2 preventing the rotation of the vertebra and a connection part 3, 4, 5.

The problem posed with these interbody cages according to the prior art is that of provisional fixation before bone fusion has taken place. Indeed, it is wvital for the cage to remain in position. The solutions according to the prior art are not satisfactory since they require direct or indirect impacting of the cage in the intervertebral space.

The major drawbacks of the devices according to the prior art lie both in the fact that they do not allow perfect stabilisation of the interbody cage in the spinal segments, particularly during extension and/or rotation movements of the spinal column and in the fact that they do not really allow the ablation of the interbody cage.

The purpose of the present invention to propose an enhanced interbody cage allowing implantation by the cervical, thoracic or lumbar route, by means of a frontal or rear surgical procedure, guaranteeing effective fixation of the cage before bone fusion and once bone fusion has taken place, and allowing the removal of the cage after bone fusion.

The purpose of the cage according to the invention is to make it possible to keep the intervertebral space constant 1n order to prevent the distraction of the vertebral bodies.

AMENDED SHEET

For this purpose, the broadest embodiment of the invention relates to an interbody spinal stabilisation cage according to claim 1.

An anchoring point is, by definition, composed of a lock comprising no degree of freedom. The interbody cage anchored in this way by anchoring means locks the vertebrae in terms of compression, extension and rotation, in order to form a perfectly attached assembly.

Preferentially, the actuation means comprise a rotation actuation head and are mobile in rotation in both directions, to allow reversibility of the anchoring means.

According to a first embodiment, the anchoring means are composed of self-tapping screws.

According to a preferred embodiment, said anchoring means have an overall S shape and the centre of gravity of the S shape coincides with the axis of the actuation means. :

Advantageously, each anchoring means comprise at least one radial cutting edge roughly perpendicular to the axis of the actuation means, to allow good penetration of the anchoring means in the bone substance when the cage is fitted and possibly during its ablation.

Advantageously, each anchoring means also comprise at least one return cutting edge roughly parallel to the main cutting edge to allow good penetration of the anchoring means in the bone substance during the ablation of the cage.

Also advantageously, each anchoring means comprise a slot, to allow bone regrowth between the arms of the anchoring means. The co-operation obtained in this way between the anchoring means and the bone regrowth

AMENDED SHEET guarantees perfect support of the vertebrae in terms of compression, extension and rotation.

In addition, the edges of these slots are preferentially at least partially cutting, to allow to 5 the production of a slit for the release of the anchoring means and the ablation of the interbody cage.

Also advantageously, the cage according to the invention comprises force locking/unlocking means of the anchoring means in their anchored position.

Finally, advantageously, said actuation means comprise in their centres a hole wherein the walls are threaded, to be able to position one or more additional components, such as a fixation screw, in the axis of the actuation means.

The invention will be understood more clearly upon reading the following description, with reference to the non-restrictive example illustrated in the appended figures where: - figure 1 represents a perspective schematic view of an interbody cage according to the invention; - figures 2, 3 and 4 respectively represent a perspective schematic view and section schematic views of an interbody cage corresponding to a first embodiment of the anchoring means of the interbody cage according to the invention; - figures 5 and 6 respectively illustrate a perspective view of two pairs of S-shaped anchoring means according to a second embodiment of the anchoring means of the interbody cage according to the invention; —- figure 7 illustrates a perspective view of an interbody cage according to the invention with one pair of anchoring means;

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- figures 8 and 9 respectively illustrate a front view of the interbody cage in figure 7, in the retracted position and in the anchoring position; - figure 10 illustrates a side view of an interbody cage according to the invention with one pair of anchoring means. - figure 11 illustrates a perspective view of an interbody cage according to the invention with a double pair of anchoring means; and - figures 12 and 13 respectively illustrate a front view of the interbody cage in figure 11, in the anchoring position and in the anchored position.

The interbody cage 1 according to the invention has an overall parallelepipedic shape and delimits a hollow inner space 4 opening by means of slots provides on the different faces, particularly on the lateral 5, 5' and front 6 faces. The inner space 4 is intended to be filled with bone fragments taken from the patient. These bone fragments are intended to initiate fusion of the vertebrae between which the interbody cage is placed.

The front face 6 comprises a slot used to access the rotation actuation head 7 of the actuation means 2.

In this way, using the actuation means, the anchoring means each have two extreme positions: a retracted position wherein they are positioned inside the cage and an anchored position wherein that have a maximum clearance outside the cage. Between these two extreme positions, the anchoring means comprise a plurality of intermediate anchoring positions.

In a first embodiment of the invention, the actuation means 2 are composed of an actuation rod equipped with a screw thread and the anchoring means 3

AMENDED SHEET are composed of two self-tapping screws 8, 9 opening onto the upper lateral face 5 and the lower lateral face 5', respectively.

The actuation rod comprises a hexagonal head for actuation with a tool and a ribbed body which co-operates with the threading of the self-tapping screws 8, 9.

In this embodiment, the main cutting edge 10 is composed of the end of the self-tapping screw thread.

In a preferred embodiment of the invention, said anchoring means 3 have an overall S shape, as illustrated in figures 5 and 6, and the centre of gravity of the S shape is positioned on the axis A of the actuation means 2, as illustrated in figure 7.

In this version, each anchoring means 3 preferentially comprise at least one radial cutting edge 11, positioned on a radius of the anchoring means, roughly perpendicular to the axis of the actuation means, on the edge of the connection arms of the anchoring means, and at least one return cutting edge 12 roughly parallel to the main cutting edge 10, as illustrated in figures 5 and 6.

Figure 6 illustrates a version of the invention wherein said main cutting edge 10 forms the base of an at least isosceles or equilateral triangle, equipped with cutting sides forming sharp edges 10',10'"'.

In this figure, each anchoring means 3 comprise two radial cutting edges 11 positioned roughly on the same radius of the anchoring means 3, on opposite edges, inside and outside, of the connection arms.

In figure 7, each anchoring means 3 comprise two radial cutting edges 11 positioned side by side on the inner face of the connection arms.

AMENDED SHEET

The cutting movement enabling the anchoring of the cage is illustrated by the arrows Fl in figures 8 and 9, while the ablation movement 1s illustrated by the arrows F2,

In addition, each anchoring means preferentially 3 comprises a slot 13 wherein the edges are at least partially cutting, as illustrated in figure 10.

To be able to lock the anchoring means 3 in the anchoring position, the cage according to the invention preferentially comprises force locking/unlocking means of the anchoring means 3 in their anchored position, composed, for example, of a boss intended to co-operate with a recess.

Preferentially, the interbody cage 1 according to the invention, as illustrated in figure 11, comprises two pairs of anchoring means 3 turning, for example, in two opposite directions, each actuation means 2 of each pair of anchoring means 3 opening onto the same front face 6.

In this version, the cutting movement enabling the anchoring of the cage is illustrated by the arrows Fl in figure 12, while the ablation movement is illustrated by the arrows F2.

Figure 13 illustrates the double S-shaped interbody cage, in the anchored position.

The cage 1s advantageously made from carbon. Such a material has a Young's modulus comparable to that of bone. The anchoring means are advantageously made from hydroxyapatite or a bound and sintered calcium phosphate compound aggregate material. The aggregates are bound with calcium phosphate compound particles. The anchoring means may also be made from titanium or stainless steel- based metal alloy.

AMENDED SHEET

The anchoring means may also be made from bicalcium phosphate, tricalcium phosphate or porous tantalum.

The invention 1s described above as an example.

Those skilled in the art will be capable of producing various alternatives, particularly for the actuation of the anchoring means and the erection by means of actuation of an anchoring device accessible via a front face.

AMENDED SHEET

Claims

1. Interbody spinal stabilisation cage (1) having a parallelepipedic shape and comprising a central hollow space (4) intended to be filled with bone fragments, characterised in that it comprises anchoring means (3) having an overall S shape and opening onto lateral faces (5, 5') connccting with adjacent vertebrae, actuated by at least one actuation means (2) opening into a front face (6), said anchoring means (3) each comprising at least one main cutting edge (10).

2. Interbody cage (1) according to the main claim characterised in that the actuation means (2) comprise a rotation actuation head (7) and are mobile in rotation in both directions, to allow reversibility of the anchoring means.

3. Interbody cage (1) according to claim 1 or 2, characterised in that the centre of gravity of the 8 shape 1s positioned on the axis of the actuation means (2).

4. Interbody cage (1) according to at least one of the above claims characterised in that said main cutting edge (10) forms the base of an at least isosceles triangle, equipped with cutting sides forming sharp edges (10',10'").

5. Interbody cage (1) according to at least one of the above claims characterised in that each anchoring means AMENDED SHEET

11 RE 8 : a Sos . ~ (3) comprise at least one radial cutting edge (11) positioned on a radius of the anchoring means.

6. Interbody cage (1) according to at least one of the above claims characterised in that each anchoring means (3) also comprise at least one return cutting edge (12) roughly parallel to the main cutting edge (10).

7. Interbody cage (1) according to at least one of the above claims characterised in that each anchoring means (3) comprise a slot (13).

8. Interbody cage (1) according to claim 7 characterised in that the edges of said slot (13) are at least partially cutting.

9. Interbedy cage (1) according to at least one of the above claims characterised in that it comprises force locking/unlocking means of the anchoring means (3) in their anchored position.

10. Interbody cage (1) according to at least one of the above claims characterised in that it comprises two pairs of anchoring means (3), each actuation means (2) of each pair of anchoring means (3) opening into the same front face (6).

11. Interbody cage (1) according to at least one of the above claims characterised in that said actuation means (2) comprise in their centres a hole (14) wherein the walls are threaded. AMENDED SHEET