DE20019520U1 - Implant - Google Patents

Description

A 55 788 u Aesculap AG & Co. KG

u - 234 Am Aesculap-Platz

16 November 2000 D - 78532 Tuttlingen

l· IMPLANT

The invention relates to an implant for insertion into a space between two vertebral bodies of the spine, with two support elements that can be placed on the vertebral bodies arranged on both sides of the space, and with a tubular cavity arranged between them, extending in the longitudinal direction of the implant, which is delimited by a bellows-shaped outer wall that can be extended in the longitudinal direction of the implant and is essentially inextensible in the circumferential direction of the cavity.

Defects in the spine are often bridged by inserting implants in place of the parts of the body that have been removed from the spine. These can be so-called intervertebral body implants that replace a single removed disc, they can be vertebral body replacement implants that replace removed vertebrae in their entirety, and there are implants that replace both removed vertebrae and removed discs.

An example of an implant that replaces a vertebral body and two adjacent intervertebral discs is described in US 4,932,975. The space created by the removal of a vertebral body and the two adjacent intervertebral discs is bridged by an implant that replaces two adjacent

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the opposite end of the implant has support elements arranged and an intermediate cavity formed by a metal bellows, such as those used in pressure cells. The construction used is relatively complex, since a large number of parts have to be combined with one another in order to take on the complex functions of this implant.

It is the object of the invention to design a generic implant in such a way that it can be manufactured in a very simple manner.

This invention is achieved in an implant of the type described above in that the outer wall is formed by a piece of tubing made of a tightly woven or knitted textile material.

It has surprisingly been found that the limitation of the hollow space between the support elements can be achieved very easily by means of such a textile tube piece. Such tube pieces are known per se and are used as vascular prostheses and as inserts in blood vessels (so-called stents). They are bellows-shaped tube pieces in which the threads used are woven or knitted so tightly that these tube pieces become so dense that liquids absorbed in them can be retained inside them. It has now surprisingly been found that

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It has been shown that these known tube pieces are suitable for forming an implant in conjunction with two support elements that can be applied to the vertebral bodies, which implant is suitable for bridging defects in the spine.

In a preferred embodiment of the invention, the hose piece can be constructed from threads consisting of polyethylene terephthalate.

In a preferred embodiment, the hose section is connected to the support elements at its ends in a liquid-tight manner. For example, the end region of the hose section can be inserted into a circumferential groove of the support elements and fixed in this position by an external bandage.

It is advantageous if the support elements are plate-shaped and extend essentially transversely to the longitudinal direction of the implant; in such a construction, the cavity is limited on the outside by the textile tube piece and on the two end faces by the two support elements.

It is advantageous if the support elements have projections on their respective outer surface, which is adjacent to a vertebral body, which penetrate into the bone material when they are placed against the vertebral body and thereby enable an intimate connection between the support element and the vertebral body. These projections can be macroscopic projections, for example, next to each other.

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These may be pins or ribs, but they may also be microscopic projections which can be achieved, for example, by roughening the outer surface or by coating the outer surface with a rough surface.

In a preferred embodiment, the support elements have openings through which the cavity is connected to the outer surface of the support elements. Filling material from the cavity can enter the contact area of the support elements on the vertebral body through these openings and contribute to an optimal connection there.

The cavity may have an inlet for a flowable filling medium.

In a first preferred embodiment, the cavity is filled with a permanently flowable or elastic substance. An implant designed in this way is preferably used as an intervertebral disc replacement, since with this implant the two opposing support elements can be pivoted against each other in the manner of an intervertebral disc and can also perform a shock absorption function. The free pivoting of the adjacent support elements is facilitated by the special design of the outer wall of the cavity, the textile tube piece easily allows pivoting, twisting around the longitudinal axis of the implant and even, to a small extent,

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lateral displacement of the two support elements, while in the radial direction the filling of the cavity is permanently limited and not expanded radially due to the lack of extensibility of the hose section in the circumferential direction.

The permanently flowable substance can be a hydrogel, for example, and silicone can be used as an elastic substance.

In another embodiment, the cavity is filled with a flowable, hardenable substance. An implant designed in this way is particularly suitable as a vertebral replacement body. With this implant, the support elements are spread open with a suitable instrument after being inserted into the gap to be bridged and placed against the vertebral bodies adjacent to the gap. As soon as the desired extension of the implant in its longitudinal direction is achieved, the cavity is filled with the flowable, hardenable substance, which then, after hardening, bridges the gap permanently and in an axially unchangeable manner.

The flowable, hardenable substance can be bone cement, for example a bone cement based on an acrylic resin.

The implants described in this way, which have a cavity, can be used as a replacement for an intervertebral disc or as a replacement for a

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Vertebral bodies are inserted, whereby the extension of the implant in the longitudinal direction of the implant is selected according to the natural dimensions of an intervertebral disc and a vertebral body, i.e. an intervertebral disc replacement implant will have a significantly smaller extension in the longitudinal direction than a vertebral body replacement implant, for example the longitudinal extension of an intervertebral disc replacement implant will be in the order of magnitude of 10 to 15 mm, the longitudinal extension of a vertebral body replacement implant in the order of magnitude of 25 to 70 mm per replaced vertebral body.

In a further preferred embodiment of such an implant, it is provided that in the longitudinal direction of the implant between the support elements there are at least two cavities which are delimited by a tubular outer wall made of a tightly woven or knitted textile material.

Such implants with multiple cavities can be used to take over the function of both an intervertebral disc and a vertebral body and thus replace both intervertebral discs and vertebral bodies.

For example, it is possible for one cavity of an implant to be filled with a permanently flowable or elastic substance and the other with a flowable, hardenable substance. Such a

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Implant can replace a vertebral body and an adjacent intervertebral disc.

A symmetrical structure is particularly advantageous, in which an implant has three cavities connected to one another lengthwise. The middle cavity is filled with a flowable, hardenable substance and the two outer cavities with a permanently flowable or elastic substance. Such an implant can replace a vertebral body with both of the intervertebral discs connected to it.

In accordance with the anatomical extension of a vertebral body and the adjacent intervertebral discs, the extension of the cavity filled with a hardenable substance in the longitudinal direction of the implant is larger than that of the cavity filled with a permanently flowable or elastic substance.

The following description of preferred embodiments of the invention serves to explain in more detail in conjunction with the drawing. They show:

Figure 1: a schematic side view of an implant serving as a vertebral replacement body;

Figure 2: a sectional view along line 2-2 in Figure 1;

Figure 3: a view similar to Figure 1 with the implant in longitudinal section;

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Figure 4: a schematic longitudinal section of an implant used as a disc replacement and

Figure 5: a schematic longitudinal sectional view of a vertebral body replacement implant, which simultaneously takes over the function of two adjacent intervertebral discs.

The implant 1 shown in Figures 1 to 3 comprises two plate-shaped support elements 2, 3 which are arranged at opposite ends of the implant 1 and enclose a cavity 4 between them which is laterally delimited by a flexible outer wall 5. The flexible outer wall 5 consists of a bellows-shaped piece of tubing made of a textile material, for example polyethylene terephthalate, in which the threads are very densely woven or knitted, so that this outer wall 5 is essentially liquid-tight. The outer wall 5 can be designed in one layer or several layers; what is important is that through the use of textile material and the bellows-shaped design, the outer wall 5 can be extended in the longitudinal direction of the implant, i.e. in the direction from one support element 2 to the other support element 3, but in the circumferential direction it is essentially not stretchable or not stretchable at all.

The two plate-shaped support elements 2 and 3 bear on the sides facing each other in the same way

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collar-shaped projections 6, 7, each of which has a circumferential groove 8 and 9, respectively; the end regions of the tubular outer wall 5 are inserted into these circumferential grooves 8 and 9 and are fixed there with the aid of a bandage not shown in the drawing, so that the cavity 4 is delimited on the front side by the two support elements 2 and 3 and on the shell side by the outer wall 5.

The two support elements 2 and 3 are constructed identically and are installed in the implant 1 in opposite orientations. They have an outer surface 11 provided with rib-shaped projections 10; in this outer surface 11 there is a central recess 12 which is connected to the cavity 4 via a connecting channel 13.

The support elements 2 and 3 are preferably made of metal, for example titanium.

Receiving openings 14 are incorporated into the support elements 2 and 3, which are open at the side and run transversely to the longitudinal direction of the implant 1, into which corresponding tools 15 of a spreading instrument 16 can be inserted; this is indicated in dash-dotted lines in Figure 3. With the help of this spreading instrument 16, it is possible to change the distance between the support elements 2 and 3, whereby the bellows-shaped folded outer wall 5 is stretched in the longitudinal direction of the implant 1.

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The implant 1 described serves as a vertebral body replacement implant. For this purpose, the implant 1 is inserted into the space 17 between two vertebral bodies 18 and 19. This space 17 was created by removing a vertebral body and the adjacent intervertebral discs. After the implant has been inserted into the space 17, the two support elements 2 and 3 are moved against the vertebral bodies 18 and 19 using a spreading instrument 16 so that the support elements 2 and 3 rest with their outer surfaces 11 against the two vertebral bodies 18 and 19. The implant is stretched so far that the two vertebral bodies 18 and 19 are in approximately the same position as they were before the vertebral body and the intervertebral discs were removed from the space 17, i.e. in a natural position.

In this position of the support elements 2 and 3, the cavity 4 is filled with a flowable, hardenable substance, for example with a bone cement based on acrylic resin. The introduction can either take place via an introduction channel 20 in a support element 2 or through an opening in the outer wall 5. This opening can be created, for example, by a small cut or by the injection needle 21 of a filling device. The flowable material filled into the cavity fills this cavity completely; in the radial direction, this material is localized by the outer wall on the cross section that is defined by the outer wall 5, which is not stretchable in the circumferential direction; in the axial direction, the distance between the two

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Support elements 2 and 3 are maintained by the spreading instrument 16 so that the filling no longer causes the support elements 2 and 3 to shift. The substance that is filled in hardens after the cavity 4 is completely filled and thus forms an essentially rigid connecting part surrounded by the outer wall 5, which permanently fixes the two support elements 2 and 3 in the position once they have been assumed. The implant made up of the two support elements 2 and 3 and the cavity 4 filled with the hardened material thus forms a largely rigid intermediate piece that fills the entire gap 17 and supports the vertebral bodies 18, 19 against each other.

A particularly intimate connection of the support elements 2 and 3 with the adjacent vertebral bodies 18 and 19 is achieved by the fact that when filling the cavity 4, part of the filling material passes through the connecting channel 13 into the recess 12 and spreads out in the connection area between the outer surface 11 and the adjacent vertebral body 18 and 19, respectively. After hardening, this thin layer of the penetrated material supports the connection between the support element and the vertebral body.

In the embodiment shown in Figures 1 to 3, the vertebral bodies 18 and 19 are connected via the implant 1 to form a single, essentially rigid body, the function of the omitted

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This type of implant does not replace intervertebral discs.

Figure 4 shows a further preferred embodiment of an implant 31 which, like the implant 1, has two support elements 32 and 33 arranged on opposite sides of the implant, which enclose a cavity 34 between them. This cavity 34 is surrounded on the shell side by an outer wall 35 which is constructed in exactly the same way as the outer wall 5 of the implant 1, but the extension in the longitudinal direction of the implant 31 is significantly smaller than in the embodiment of Figures 1 to 3.

In this embodiment, too, the support elements 32 and 33 have collar-shaped projections 36 and 37 facing one another with circumferential grooves 38 and 39, respectively, into which the edge regions of the outer wall 35 are inserted in the same way and fixed by bandages (not shown).

The outer surface 41 of the two support elements 32 and 33 is provided with rib-shaped projections 40, just as in the embodiment of Figures 1 to 3, but a central recess and a connecting channel to the interior of the cavity are missing. With this implant, it is also not absolutely necessary to provide receiving openings for a spreading instrument.

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The cavity 34f in this implant 31 is filled with a flowable substance that either remains permanently flowable or hardens to a rubbery elastic state. A filling with a hydrogel, for example, remains permanently flowable, whereas a silicone filling is a permanently elastic, non-flowable filling. Such a filling makes it possible to pivot the two plate-shaped support elements 32 and 33 against each other to a small extent, and the support elements 32 and 33 can also perform small rotational movements around the longitudinal axis of the implant. The implant 31 shown in Figure 4 serves as a replacement for an intervertebral disc and is therefore inserted into the intervertebral space 42 between two adjacent vertebral bodies 43, 44 after the removal of an intervertebral disc. In this embodiment of the implant, the cavity can be filled before implantation or after insertion into the intervertebral space 42. If the cavity 4 is filled before insertion, the adjacent vertebral bodies 43 and 44 are separated by suitable spreading instruments so that the implant can be inserted into the intervertebral space. After insertion, the two vertebral bodies 43 and 44 are then lowered onto the outer surfaces 41 so that they are kept at a distance from each other that corresponds to the distance achieved by the natural, removed intervertebral disc.

In the embodiment of Figure 5, the constructions of the vertebral body replacement implant are

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ing implant of Figures 1 to 3 and the implant of Figure 4 serving as an intervertebral disc replacement.

The implant 51 of Figure 5 has two support elements 52 and 53 at opposite ends, which are constructed in the same way as the support elements 32 and 33 of the implant of Figure 4. On the sides of these two support elements 52 and 53 facing each other, there is a cavity 54 which, in the same way as the cavity 34 of the implant 31, is surrounded by an outer wall 55 which is a bellows-shaped, textile tube piece. Each of the two outer walls 55 is fixed in a circumferential groove 58 or 59 on a collar-shaped projection 56 or 57 of the support element 52 and 53 in the manner described. The opposite ends of the two outer walls 55 are each inserted into a circumferential groove 60 or 61 of intermediate walls 62 or 63 and secured there with bandages (not shown); These intermediate walls 62 and 63 run parallel to the plate-shaped support elements 52 and 53 and close off the cavities 54.

The two intermediate walls 62 and 63 form between themselves a further hollow space 64 which is closed off by a further outer wall 65 in the form of a textile, bellows-shaped piece of hose. This piece of hose is inserted with its end sections into a further circumferential groove 68 and 69 of a collar-shaped projection 66 and 67 of the intermediate walls 62,

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63 and secured there by means of a bandage (not shown).

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In this way, this implant 51 has three cavities 54, 64, 54 lying one behind the other in the longitudinal direction of the implant, wherein the middle cavity 64 has a significantly greater extension in the longitudinal direction than the outer cavities 54.

These two outer cavities 54 are filled with a permanently flowable or elastic substance and thus form intervertebral disc replacement bodies, while the middle cavity 64 is filled with a hardenable substance and thus forms a vertebral replacement body. The entire implant covers

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Thus, after insertion into a gap 70, it takes over the function of the parts removed from this gap 70, namely a vertebral body and the two adjacent intervertebral discs.

In the embodiment shown, the outer walls 55 and 65 are formed by separate pieces of tubing. It would also be possible to form all the outer walls by a continuous piece of textile tubing; this would simplify the manufacture of this implant even further.

Claims (16)

1. Implant for insertion into a space between two vertebral bodies of the spine with two support elements that can be placed on the vertebral bodies arranged on both sides of the space and with a tubular cavity arranged between these, extending in the longitudinal direction of the implant and delimited by a bellows-shaped outer wall that can be extended in the longitudinal direction of the implant and is essentially not stretchable in the circumferential direction, characterized in that the outer wall ( 5 ; 35 ; 55 , 65 ) is formed by a piece of tubing made of a tightly woven or knitted textile material. 2. Implant according to claim 1, characterized in that the tube piece is constructed from threads consisting of polyethylene terephthalate. 3. Implant according to one of claims 1 or 2, characterized in that the tube piece is connected at its ends in a liquid-tight manner to the support elements ( 2 , 3 ; 32 , 33 ; 52 , 53 ). 4. Implant according to one of the preceding claims, characterized in that the support elements ( 2 , 3 ; 32 , 33 ; 52 , 53 ) are plate-shaped and extend essentially transversely to the longitudinal direction of the implant ( 1 ; 31 ; 51 ). 5. Implant according to claim 4, characterized in that the support elements ( 2 , 3 ; 32 , 33 ; 52 , 53 ) have projections ( 10 ; 40 ) on their respective outer surface ( 11 ; 41 ) adjacent to a vertebral body ( 18 , 19 ; 43 , 44 ) which, when in contact with the vertebral body, penetrate into its bone material. 6. Implant according to one of claims 4 or 5, characterized in that the support elements ( 2 , 3 ) have openings ( 13 ) through which the cavity ( 4 ) is connected to the outer surface ( 11 ) of the support elements ( 2 , 3 ). 7. Implant according to one of the preceding claims, characterized in that the cavity ( 4 ) has an inlet ( 20 ) for a flowable filling medium. 8. Implant according to one of the preceding claims, characterized in that the cavity ( 34 ; 54 ) is filled with a permanently flowable or an elastic substance. 9. Implant according to claim 8, characterized in that the permanently flowable substance is a hydrogel. 10. Implant according to claim 8, characterized in that the elastic substance is silicone. 11. Implant according to one of claims 1 to 7, characterized in that the cavity ( 4 ; 64 ) is filled with a flowable, hardenable substance. 12. Implant according to claim 11, characterized in that the flowable, hardenable substance is bone cement. 13. Implant according to one of the preceding claims, characterized in that in the longitudinal direction of the implant ( 51 ) between the support elements ( 52 , 53 ) there are at least two cavities ( 54 , 64 ) which are delimited by a tubular outer wall ( 55 , 65 ) made of a tightly woven or knitted textile material. 14. Implant according to claim 13, characterized in that in an implant with two cavities, one cavity is filled with a permanently flowable or an elastic substance and the other with a flowable, hardenable substance. 15. Implant according to claim 13, characterized in that in an implant ( 51 ) with three longitudinally adjoining cavities ( 54 , 64 , 54 ), the middle cavity ( 64 ) is filled with a flowable, hardenable substance and the two outer cavities ( 54 ) with a permanently flowable or elastic substance. 16. Implant according to one of claims 14 or 15, characterized in that the extent of the cavity ( 64 ) filled with a hardenable substance in the longitudinal direction of the implant ( 51 ) is greater than that of the cavity ( 54 ) filled with a permanently flowable or elastic substance.