EP1572040A2

EP1572040A2 - Implant used in procedures for stiffening the vertebral column

Info

Publication number: EP1572040A2
Application number: EP03810989A
Authority: EP
Inventors: Fritz Magerl; Roger Stadler
Original assignee: Sepitec Foundation
Current assignee: Sepitec Foundation
Priority date: 2002-11-14
Filing date: 2003-11-14
Publication date: 2005-09-14
Also published as: AU2003301949A8; WO2004043304A3; WO2004043304A2; AU2003301949A1; JP2006506116A; US20060116767A1; CA2505926A1; DE10253170A1

Abstract

The invention concerns an implant in the form of a compression-resistant hollow body (1), used in procedures for stiffening the vertebral column (2). The hollow body (1) consists of two open receptacles (3, 4) mutually oriented which interlock and form the implant proper (cage). The two receptacles (3, 4) can be separated by compression through insertion of a filling material, thereby producing an expansion of the hollow body (1) after it has been implanted.

Description

Subject: implant for use in stiffening operations on the spine

Description:

The invention relates to an implant for use in stiffening operations on the spine.

Such an implant is referred to in medical technology as a cage, which is used in stiffening operations on the spine after the intervertebral disc has been cleared into the intervertebral space. The implant is filled with bone or bone replacement material taken from the patient. In addition to hollow cages, there are also a few full cages.

These implants are implanted from the front through a front access to the spine (UP = anterior lumbar interbody fusion). The technique of implantation from behind (PLIF = posterior lumbar interbody fusion) generally uses two cages, i.e. one from each side (bipolar technique).

Pain that cannot be influenced with conservative treatment and often instability-related pain, spinal cord or nerve root compression, malpositions and tumors are indications for interbody spondylodesis. As part of the surgical intervention, the causes of pain and pathological changes are eliminated and the stability of the spine is restored with a spinal fusion.

In an interbody spinal fusion, intervertebral discs are always removed. It is also not uncommon for vertebral bodies to be removed in whole or in part. The resilience of the vertebral body column must therefore be restored in any case. This can happen, for example, with pressure-resistant bone chips removed from the patient and clamped between the vertebral bodies. However, the load capacity of such chips is often uncertain. Because the availability of suitable bone chips is also limited and the morbidity caused by chip removal is considerable, place of autogenous bone chips increasingly made of metal or other materials flameproof implants. In technical terms, the implant is called a cage.

In spite of the fact that at least intervertebral discs are always cleared out during inter-corporeal spondylodesis, the stability of the spine must always be restored. This can e.g. B. happen with the patient's pressure-resistant bone chips. Because the resilience of such chips is often uncertain and their availability is limited, and the morbidity caused by chip removal can be considerable, bone substitute materials and pressure-resistant intervertebral implants (also called cages) are increasingly being used instead of autogenous bone chips.

Intervertebral implants can be inserted from the front in all areas of the spine (ALIF = anterior lumbar interbody fusion); on the lumbar spine also from behind (PLIF = posterior lumbar interbody fusion), from the side or from the side behind. One or two implants are used per intervertebral disc space. If two implants are inserted from behind through two separate openings in the intervertebral disc ring, one speaks of a biportal implantation. With a uniportal implantation, the intervertebral disc ring is only opened at one point.

An intervertebral implant functions as a pressure-absorbing placeholder, which stabilizes the spinal fusion, ensures the position of the vertebral bodies relative to one another and ensures that a solid bone bridge can form between the vertebral bodies. Bone or bone substitute material filled into and / or deposited around the implants forms the matrix for new bone formation. The stability of the spinal fusion plays a crucial role in the ossification process. Movements occurring within the spinal fusion delay or prevent bony consolidation. Pedicle systems or translaminar screw connections are used for additional stabilization of the spondylodesis.

In addition to the therapeutic, the distraction also has a mechanical meaning: The accompanying stretching of the soft tissues generates a force that jams the intervertebral implants between the vertebral bodies. This prevents movement conditions within the spinal fusion and also reduces the risk of secondary implant dislocation, which can have serious consequences.

When implanting intervertebral implants, it is often very difficult, particularly with minimally invasive and one-sided (uniportal) implantation technique, to achieve effective distraction.

With cages you can bridge intervertebral disc spaces or additionally replace parts of vertebral bodies as well as entire vertebral bodies. Cages can be implanted from the front in all areas of the spine (ALIF), and also from the back on the lumbar spine (PLIF). In a spinal fusion, bone or bone substitute material is inserted between two or more vertebral bodies (interbody spondylodesis) or attached over the posterior vertebral elements of two or more vertebrae (dorsal spondylodesis). Over the course of several months, this creates a bony bridge that connects the vertebrae and thus eliminates the instability that causes pain. The prerequisite for ossification is that the relevant section of the spine is immobilized until the bone bridge is sufficiently firm.

As part of a spinal fusion, the reduced vertical distances between the vertebral bodies due to narrowing of the intervertebral discs must also be normalized and axis deviations of the spine eliminated. Since the increase in vertical vertebral body distance through instrumentally induced "distraction" has a strong decompressing effect on both the nerve structures and the intervertebral joints, distraction is always an essential part of the procedure.

The purpose of a cage is to act as a pressure-absorbing placeholder, which ensures that the vertebral bodies grow together in the desired position. The latter happens through newly formed bones, which creates a bony bridge between the vertebral bodies. Bone or bone substitute material filled in and / or deposited around cages serves as a matrix for bone formation. The ossification process takes several months depending on various factors. The stability of the spinal fusion plays a crucial role because repetitive movements between the cage and the vertebral bodies can greatly delay or prevent the bony development of the spinal fusion. Surgical stiffening This section of the spine is called spinal fusion. Pain, spinal cord or nerve root compressions that cannot be influenced by conservative treatment measures as well as malpositions are indications for spondylodesis. Pain can come from all pathologically changed structures of the spine. In many cases, they are based on an "instability" of the movement segment, caused by degenerative changes in the intervertebral disc and intervertebral joints of the movement segment. Narrowings of the spinal canal or the intervertebral holes are responsible for the development of spinal cord or nerve root compression. With the surgical intervention, the pathological changes are eliminated and the stability of the spine is restored by the spinal fusion.

An essential requirement for the surgical technique is to normalize reduced distances between the vertebral bodies or to eliminate vertebral displacements. In addition to the therapeutic effect, increasing the intervertebral distance has a not insignificant mechanical meaning: The tension in the paravertebral soft tissues associated with the spreading of the vertebral bodies generates a counterforce that presses the vertebral bodies onto the cage and clamps it between the vertebral bodies. This prevents harmful movements between the cage and the vertebral bodies and reduces the risk of secondary cage dislocation, which can have serious consequences.

The object of the invention is therefore to simplify the technique of cage implantation and thus, as well as to reduce the need for surgical trauma due to the simpler use of less invasive surgical techniques.

This is achieved according to the invention in that the implant is formed by a circumferentially closed hollow body made of at least two boxes, one inside the other, open towards one another and telescopically movable, which can be pressed apart by introducing filler material or by using a filling made of an elastomer. to expand the hollow body. cause. An expandable hollow body (cage) has thus been created which, in a relatively small size, that is to say when the containers are pushed together, can be effortlessly inserted into the intervertebral space or other defect in the vertebral body column, where it can then be expanded to the required size. This means that it can also be used on one side from behind (uniportal PLIF). In addition, only one can be implanted instead of the usual two cages. The previously otherwise necessary expansion process is thus carried out by the hollow body itself.

An elastic intervertebral implant has also been created by the invention in order to promote the bony development of the spinal fusion by reducing both the stress differences occurring in the contact zone of the bone and the formation of new bones by the elasticity or reduction of the stress shielding "is stimulated. The implant also extends the vertical vertebral body distance.

When using an intervertebral implant, the difference between the elasticity of the bone and that of the implant can play a significant role. The bone of the vertebral body is elastically more deformable than the implants made of metal or polymer. For this reason, stress peaks occur in the contact zone of the bone among the thousands of daily changes in stress, which can cause microfractures in the bone of the contact zone as a result of material fatigue. The damaged bone is then broken down and replaced with connective tissue. This replacement can be recognized radiologically from a more or less wide brightening hem surrounding the cage. The replacement of the solid bone with soft connective tissue leads to loosening of the cage (implant) or to instability of the spinal fusion. As a result of the instability, the formation of the bony bridge between the vertebral bodies can also be omitted; H. Pseudarthrosis can occur. This is tantamount to treatment failure.

The described process is intensified if the spondylodesis is not completely stable a priori, ie if movements between the vertebral bodies and the implant are possible from the start. If the vertebral body z. B. can move slightly away from the implant when tilted backwards, the tension in the bone drops to zero. Because in In such a case, the stresses can rise from zero to the maximum, the stress differences responsible for the fatigue fractures become particularly large.

The present invention now creates an elastic hollow body (HK) for restoring the spinal column (WS) stability, which can be used in the context of intercorporeal spondylodesis between the vertebral bodies in the intervertebral disc space or in defects of the vertebral body column (WkS). The hollow body consists of two parts inserted into each other like a box and is filled with a tissue-compatible elastomer. By approximating the elasticity of the implant to that of the bone, it is possible to avoid high changes in tension that occur in the contact zone of the bone with the implant during cyclical loading and would lead to the bone being broken down with subsequent instability there. The ossification of the bone graft by approximating the elasticity of the implant to that of the bone is promoted and thus the success of an interbody spinal fusion is ensured.

A simple construction is provided when two boxes are placed one inside the other in a box-like manner. It is then only necessary to provide two precisely fitting parts. The hollow body (cage) according to the invention is thus designed in such a way that it meets the biomechanical requirements even when only one cage is implanted. This and the telescopic principle greatly simplify the technique of cage implantation, especially that of minimally invasive and uniportal.

Another advantageous measure is that the container can be connected to a feed hose. A proper supply of the filling material can thus be ensured as soon as the container is inserted. In addition, access is only required from one side (just from behind).

In order to enable a simple and uncomplicated supply of the filling material, it is proposed that the supply hose can be connected at its other end to a device for generating the necessary filling pressure.

The connection hole for the supply tube can also be used at the same time for the insertion of the hollow body, in order to thereby secure the implantation to accomplish. For this purpose, it is proposed that an instrument for inserting the hollow body can be attached to the bore provided for connecting the feed hose.

It is particularly advantageous that the filling material is formed from a material that is compatible with the tissue, remains liquid or self-hardening after a liquid phase. The pressure required for the expansion of the container can thus be exerted precisely with the material which is the best solution for the application.

In order to achieve a better fit and a better integration of the implanted hollow body in its osseous bearing, it is provided that the hollow body is structured or coated on a part or on its entire surface.

If it is further provided that the containers forming the hollow body are sealed against one another, then filler material can be effectively prevented from escaping from the containers.

It is further proposed that the containers forming the hollow body are mutually adjustable, this adjustment movement being limited to an area that always ensures mutual overlap of the containers. This also ensures that filling material can escape from the containers unintentionally.

In this context, it is advantageous if the adjustment movement between the two containers is limited by locking screws engaging in a slot. This can prevent the containers from being pushed too far apart.

In a further embodiment variant it is provided that the elastomer is filled into the inner part of the hollow body. The elastomer thus has the purely the function of forming the desired elasticity, so that the elastomer never comes into direct contact with the area surrounding the implant.

One embodiment provides that the elastomer completely or partially fills the hollow body. Variations can also be created, including with different areas of different elasticity. The elastomer should preferably Completely fill the interior of the implant with elastomer to prevent gas or liquid from being pressed out or drawn into the implant during loading and unloading.

In this context, it is also possible for the elastomer filled into the hollow body to rest loosely or firmly and sealingly on the inner side walls of the hollow body.

If it is further provided that the inner surfaces of the upper and lower walls of the box-like containers of the hollow body penetrate into the filled elastomer under load, the most varied distribution of forces and different forces in the implanted state of the implant can be specifically addressed.

In a further embodiment variant it is provided that under the filled elastomer, i.e. a cavity is left between the elastomer and the lower wall of the container of the hollow body which is inserted into one another in a box-like manner. As a result, the elasticity of the implant can be increased even further, or additional means for changing or increasing the elasticity can be used.

In a special embodiment, it can be provided that a hermetically sealed gas bubble is incorporated in the elastomer. This means a very simple and also structurally very effective configuration for increasing the elasticity.

In a special embodiment variant, it is proposed that a device, for example in the form of a clamping screw, be attached to the hollow body in order to allow the hollow body, which was compressed to a reduced height before the implantation, to expand after the implantation. This facilitates the implantation and can also increase the vertical vertebral body distance (distraction). In addition, the intervertebral implant receives a preload, which keeps the implant in constant contact with the vertebral body and reduces the harmful voltage differences. For an optimal possibility of inserting the implant, a configuration is proposed in which the outer container of the box-like hollow body has a wedge-shaped insertion end. This can significantly improve the distracting effect.

It is provided in a structurally simple manner, depending on the shape to be selected in particular and the special purpose of the implant, that the implant be made of metal, polymer or a composite material.

It is further proposed that elements or materials which provide radiological shadow are incorporated into the implants during manufacture from polymer or composite material. This allows the implants to be made radiologically visible.

A constructive design of the implant according to the invention is per se possible in various ways. An advantageous embodiment is given, however, when the pressure-absorbing parts of the hollow body have the shape of a low cylinder or prism, with flat or slightly curved base plates and cover plates which are parallel to one another or slightly inclined towards one another.

So that the implant can also be implanted in a simple manner, it is proposed that it be designed to attach an implantation instrument. This ensures that the implant itself is properly gripped and inserted.

An advantageous embodiment further provides that the surface of the implant is structured and / or coated. This also ensures optimal positional securing of the implant in the implanted position and better integration into the bony implant bed.

Further features according to the invention and special advantages are explained in more detail in the following description with reference to the drawing. Show it: 1 shows a section through a section of a spine, the use of an implant in the form of an expandable hollow body (cage) being evident;

2 shows a basic drawing of the pressure-resistant implant according to the invention;

3 shows a side view of the implant seen from the same side as in FIG. 2, the two containers of the implant designed as a hollow body being shown pulled apart;

FIG. 4 shows a view of the implant from above, a connection element for a supply line also being shown, as in FIG. 3;

5 shows an oblique view of the implant with a connected insertion instrument;

Fig. 6 is an oblique view of a special embodiment of the implant with a wedge-shaped introducer.

7 shows a section of an intervertebral disc space with an inserted implant of another embodiment;

8 shows a section through the implant used according to FIG. 7 in a simplified representation;

9 and 10 show sections through an implant in the simplified representation, the compressed position being shown once and the expanded position being shown once;

11 and 12 show sections through an implant in a simplified representation, the compressed position being shown once and the expanded position being shown once, and a hermetically sealed gas bubble being provided as an additional elastic element;

13 shows an oblique view of a special further embodiment of an implant.

An implant in the form of a flameproof hollow body 1 for use in stiffening operations on the spine 2 should, after the intervertebral disc (s) and / or after partial or total resection of vertebral bodies, be moved ventrally or dorsally into the ent existing defect can be used and expanded to the required size in the implanted position. This hollow body 1 is formed from at least two boxes 3 and 4, which are inserted into one another in a box-like manner and face each other, and which fit exactly into one another, so that a corresponding pressure build-up in the hollow body is also possible in order to achieve the necessary expansion pressure. The pressure build-up is achieved by introducing filler material into the interior 13, whereby the two containers 3 and 4 are pressed apart and thus cause the hollow body 1 to expand in the vertical direction.

The hollow body 1 is used in the pushed-together state of the two containers 3 and 4, possibly with the aid of an instrument 5 connected to the cage opening for the feed. In the pushed-together state, the cage has relatively small dimensions. After the introduction, the filling material is pressed from a vessel with a device for generating pressure through a removable feed hose 6 or another feed line with the required pressure into the hollow body 1. The thus expanding hollow body 1 completely fills the defect, extends the distance between the vertebral bodies and generates the counterpressure required for jamming the cage. The filling material must be perfectly compatible with the tissue and be so viscous that it flows well through the feed tube 6 but cannot escape from the cage.

Possible fillers are a tissue-compatible liquid medium or a tissue-compatible material that is cold-curing itself and after the liquid phase. In the case of a liquid medium, a non-return valve attached to the cage is required to prevent the filler from flowing back, as well as a sealing screw with which the feed opening on the gage can also be closed. If a self-curing material is used, the feed tube is twisted off the gage after the polymer has cured.

Part of the bone or bone replacement material is deposited in the defect before the cage is introduced, so that it finally comes to rest in front of the cage. The other part is plugged next to and behind the cage after removing the supply hose. This ensures that a sufficiently strong bone bridge can form around the cage.

It has been assumed that at least two containers 3 and 4 are inserted into one another to form the hollow body 1. In such a case, two boxes are inserted into one another like boxes. Within the scope of the invention, however, it would also be entirely possible to be able to push out more than two containers radially in the manner of a drawer on the circumference of a hollow body 1. When building up a pressure inside the Hollow body 1 can then be triggered expansion movements in several directions. Another variant also results from the fact that several containers 4 are provided, which are inserted into one or more recesses of the container 3. It is also possible that there is a separate supply hose for each container 3, so that a different pressure could also be built up for different areas.

The feed hose 6 can be connected to the hollow body 1 in various ways. For example, it is possible to plug or screw on a connector 7 attached to the cage. A type of bayonet lock or direct connection or screwing of the connection to the cage would also be conceivable. When using a hardening material, it must be ensured that the feed hose 6 can be removed after the material has hardened.

The opening 8 of the cage for fastening the supply tube 6 can also be used to attach an instrument 5 which is suitable for inserting the cage into the defect.

The material from which the hollow body itself is formed can in principle be varied: metal, polymer or a composite material. It would also be conceivable to also manufacture the cage itself from bone substitute material or from a self-dissolving material, so that it is finally also replaced by bone. The latter assumes that a perfectly tissue-compatible and resorbable medium was used as the filling material.

In order to promote the growth of the bone on the cage, the surface of the containers can be structured or coated in whole or in part.

In order to prevent the overlapping surfaces of the cage halves from becoming too small when the cage expands, a device is provided which prevents the cage halves from being pressed apart too much. This device can e.g. B. consist of a pin or a screw 9, which / which is fixed in the outer part of the cage and engages in a groove 9 'of the inner container 4. It would also be possible to have one or more sealing rings in the manner of piston seals that run parallel to the end plates of the cage and which, when the maximum permitted expansion is reached, abut against a strip or other elements of the inner surface of the outer container 3. The essential features of the invention lie in particular in the design of a telescopically vertical, possibly also radially expandable cage consisting of at least two containers for stabilizing the vertebral body column. The force required for expansion is generated by filling material pressed into the hollow body (cage). The filling material is pressed into the cage from a pressure-generating device via a feed hose attached to the cage. Tissue-compatible liquid and, after a liquid phase, self-hardening materials can be used as filling material. Suitable antibiotics can be added to the filling material to reduce the risk of infection. The containers (cage parts) must fit exactly together or be sealed in such a way that no filling material can escape. Devices are provided which limit the expandability of the cage in such a way that the contact surfaces of the cage containers are always sufficiently large and in particular prevent the containers from being pushed apart completely.

An instrument 5 for inserting the cage into the defect can also be connected to the bore for the feed. In order to facilitate the growth of the bone on the cage, the surfaces of the cage containers can be structured or coated.

According to the invention, after filling, the cage does not contain any dead spaces in which bacteria could accumulate. The cage can be implanted ventrally or dorsally into the defect in the area of the spinal column. Depending on the particular circumstances and requirements, one or more uni or biportal cages can be used to stabilize the spine.

The cage (the hollow body) essentially has the following devices and features: The implant is cylindrical or bean-shaped (see in particular FIGS. 4 to 6). The upper and lower surfaces of the containers 3 and 4 are slightly curved both in the direction of the longer and in the direction of the shorter diameter. The ends of the part with the longer diameter are each of the same height. In contrast, the front wall of the part is slightly lower than the rear wall. In the embodiment shown in FIG. 6 it can be seen that a supplementary structural design can be equipped with a wedge-shaped insertion part 10 arranged at one end of the container 3. As a result, an effect that expands this space can be achieved even when it is introduced into the disc space. The part of the implant opposite the insertion part 10 is rounded and has the bore 8 for receiving the instrument 5, which implantation of the cage can be used. The following devices are provided to facilitate the rotation of the implant into the definitive transverse position: from the transition of the insertion part 10 into the container 3, the upper and lower front edges 11 of the implant are sharp-edged. The front edges 12 are gradually rounded towards the end of the implant opposite the insertion part 10.

The sharp edges cut into the cover plates as soon as the implant is inserted into the intervertebral disc space from the back or laterally. The implant therefore begins to rotate in the desired transverse direction as soon as it is inserted. Due to the rod-shaped insertion instrument 5 attached to its rear end, the implant is initially additionally steerable. The instrument 5 is removed as soon as it has reached the limit of the insertion opening and can no longer be pivoted further. The implant is then hammered in by a ram attached to its rear end and simultaneously rotated into the final position.

Such implants can basically be used in all areas of the spine: on the cervical, thoracic and lumbar spine from the front, and on the lumbar spine also uniportally or biportally from the rear, from the side or from the side. A prerequisite for the applicability is that the shape of the two containers is specially designed according to the anatomical conditions of the intended implantation site (region of the spine) as well as the intended implantation technique.

In the embodiment according to FIGS. 7 to 13, the implant is designed as a hollow body 1 filled with an elastomer 12, the hollow body 1 consisting of at least two containers 3 and 4 which are inserted into one another in a box-like manner and telescopically movable in the longitudinal axis of the body. The elastomer 12 is filled into the inner container of the implant, this elastomer 12 completely or partially filling the hollow body 1. The elastomer 12 lies loosely or firmly and sealingly on the inner side walls of the container 4 of the hollow body 1. The inner surfaces of the upper wall 16 and the lower wall 15 of the containers 3 and 4 of the implant are designed in such a way that they can penetrate into the elastomer 12 when loaded. To increase the elasticity, a cavity can either be left under the elastomer 12, ie between the elastomer 12 and the lower wall 15 of the implant, or, as can be seen in the embodiment according to FIGS. 11 and 12, a hermetically sealed gas bubble 17 can be inserted into it Elastomer 12 can be incorporated.

A device is attached to the implant, e.g. B. in the form of a clamping screw 18, which makes it possible for the implant compressed to a reduced height before the implantation to expand only after the implantation, that is to say after the clamping screw 18 has been loosened. So that the area of expansion cannot lead too far, the end of the clamping screw 18 engages in a slot 19 (see FIG. 13), so that the pushing of the container 4 out of the container 3 of the hollow body 1 is limited to a certain extent.

To increase the mentioned distracting effect, the outer container 3 of the implant can have a wedge-shaped insertion part 10.

Functionally, such an intervertebral implant with a wedge end consists of two parts. This is shown by way of example in FIG. 8. The two parts are the container 3 with the wedge-shaped insertion part 10 and the container 4 of the implant. The shape of the two containers depends on the area of the spine and the technique with which the implant is to be used.

The containers have the following basic shape: it is a blunt, wedge-shaped insertion part 10, which has its base continuously attached to that side of the container 3 with which the implant is inserted into the intervertebral disc space. The upper and lower surface of the insertion part 10 are flat and inclined in such a way that the wedge height decreases from the wedge base to the wedge end. The end of the wedge opposite the wedge base is vertical in the side view and rounded in the top view.

The pressure-receiving containers 3 and 4 can have the shape of a low cylinder or prism, with flat or slightly curved, parallel or parallel Base and cover plates slightly inclined towards each other. The implants can have a device for attaching an implantation instrument. The surfaces of the implants can be structured and / or coated.

The elastic intervertebral implants can consist of metal, polymer or composite material. In order to make the position of radiologically invisible implants made of polymer or composite material visible in the body, radiological shading elements or materials are incorporated into the implants.

In the context of the invention, it is possible to form the hollow body 1 from more than two boxes 3 and 4 inserted one into the other in a box-like manner. It would be conceivable, e.g. to form the container 4 from a plurality of subareas which can be moved separately and elastically relative to the container 3. It would then also be possible to completely or partially fill the different partial areas with elastomers of different elasticity.

With the implant according to the invention, the following implantation technique has become possible: After possibly extending the intervertebral disc space or the defect with a suitable instrument (for example, a pair of spreading pliers), the height of the vertical vertebral body distance is measured and the implant selected that is compressed (reduced in height) Condition is still insertable into the disc space. The implant is pressed or hammered into the intervertebral disc space, possibly with the help of an implantation instrument attached to it. After the final positioning, the clamping screw 18 is loosened so that the implant can expand in the vertical direction.

In the case of uniportal dorsal or dorsolateral application technology, the implants must be rotated from the initial sagittal or oblique implantation direction to the frontal direction during the implantation, in particular if only one implant is inserted into the intervertebral disc space. The desired jamming of the implant can be extremely difficult or impossible to rotate.

The uniportal intervertebral implant essentially has the following devices and features: The implant has a bean shape (see in particular FIG. 13). The top and The bottom surface of the containers 3 and 4 are slightly curved both in the direction of the longer and in the direction of the shorter diameter. The longer diameter ends of the container are each of the same height. In contrast, the front wall of the container is slightly lower than the rear wall. The section of the implant opposite the insertion part 10 is rounded and can have a device for receiving an instrument, which can be used for clamping and implantation.

The following devices are provided to facilitate the rotation of the implant: From the transition of the insertion part 10 into the container 3, the upper and lower front edges of the implant are sharp-edged. The front edges are gradually rounded towards the end of the implant opposite the insertion part 10. On the upper and lower surface of the container 3, incisions running parallel to the front edges can be made against the part 10, the rear surface of which is perpendicular to the respective surface and the front surface of which runs flat against the surface of the implant. These cuts act as guide grooves.

The sharp edges and the guide grooves cut into the cover plates as soon as the implant is inserted into the intervertebral disc space from the back or laterally. The implant therefore begins to rotate in the desired direction as soon as it is inserted. The implant is initially additionally steerable by means of a rod-shaped insertion instrument attached to its rear end, which can also function as a clamping screw 18. The instrument is removed as soon as it has reached the limit of the insertion opening and can no longer be pivoted. The implant is then hammered in by a ram attached to its rear end and simultaneously rotated into the final position.

Such intervertebral implants can basically be used in all areas of the spine: on the cervical, thoracic and lumbar spine from the front, and on the lumbar spine additionally uni- or biportally from behind, from the side or from the side behind. The prerequisite for the applicability is that the shape of the two implant parts corresponds to the anatomical conditions of the intended implantation site (region the spine) as well as the intended implantation technique.

Instead of the gas bubble 17 formed in the elastomer 12 or also in addition to such a configuration, a further spring element could be provided in a cavity between the lower wall 15 of the container 3 and the inserted and filled container 4 filled with elastomer 12 in order to increase the elasticity of the entire implant increase. Here would be e.g. the use of a spring element in the form of a spiral, helical or leaf spring is possible, or a further insert in the form of an elastomer could be provided, which possibly has a different elasticity than the elastomer 12 in the container 4.

Since the elastomer 12 itself has the effect of a spring, it would in principle also be possible, and to be classified under the term elastomer, to design this elastomer itself as a spring, so that instead of a filling made of an elastomeric filler, one or more spiral, helical or leaf springs (s) can be used.

Claims

claims:

1. Implant for use in stiffening operations on the spine, characterized in that the implant is formed by a circumferentially closed hollow body from at least two box-like nested, mutually open, telescopically movable containers (3, 4), which are formed by introducing filler material or can be pressed apart by using a filling made of an elastomer (12) in order to bring about an expansion of the hollow body (1).

2. Implant according to claim 1, characterized in that two boxes (3, 4) placed one inside the other are provided.

3. Implant according to claims 1 and 2, characterized in that it can be connected to a feed tube (6).

4. Implant according to claim 3, characterized in that the supply tube (6) can be connected with its other end to a device for generating the necessary filling pressure.

5. Implant according to one of claims 1 to 4, characterized in that an instrument (5) for inserting the hollow body (1) can be attached to the bore (8) provided for connecting the supply tube (6).

6. Implant according to claim 1, characterized in that the filling material is formed from a tissue-compatible material that remains liquid or self-hardening after a liquid phase.

7. Implant according to one of claims 1 to 6, characterized in that the hollow body is structured or coated on a part or on its entire surface.

8. Implant according to one of claims 1 to 7, characterized in that the containers (3, 4) forming the hollow body are sealed off from one another.

9. Implant according to one of claims 1 to 8, characterized in that the containers (3, 4) forming the hollow body are mutually adjustable, this adjustment movement being limited to a region which always overlaps the containers (3, 4). guaranteed.

10. Implant according to claim 9, characterized in that the adjustment movement between the two containers (3, 4) is limited by locking screws (9) engaging in a slot (10).

11. The implant according to claim 1, characterized in that the elastomer (12) is filled into the inner part of the hollow body (1).

12. Implant according to claim 1 or 11, characterized in that the elastomer (12) completely or partially fills the hollow body (1).

13. Implant according to one of claims 1, 11 and 12, characterized in that the elastomer (12) filled into the hollow body (1) lies loosely or firmly and sealingly on the inner side walls of the hollow body (1).

14. Implant according to claim 1, characterized in that the inner surfaces of the upper and lower walls (16, 15) of the box-like nested containers (3, 4) of the hollow body (1) penetrate into the filled elastomer (12) when loaded.

15. Implant according to claim 1, characterized in that a cavity is left under the filled elastomer (12), ie between the elastomer (12) and the lower wall (15) of the box-like nested container (3, 4) of the hollow body (1) ,

16. The implant according to claim 1, characterized in that a hermetically sealed gas bubble (17) is incorporated in the elastomer (2).

17. Implant according to claim 1 or one of the preceding claims, characterized in that on the hollow body (1) a device e.g. is attached in the form of a clamping screw (18) in order to allow the hollow body (1) compressed to a reduced height before the implantation to expand after the implantation.

18. Implant according to claim 1 or one of the preceding claims, characterized in that the outer container (3) of the box-like hollow body (1) has a wedge-shaped insertion end (10).

19. Implant according to one of claims 1 to 18, characterized in that it is made of metal, polymer or a composite material.

20. Implant according to claim 19, characterized in that radiologically shadowing elements or materials are incorporated into the implants in the manufacture of polymer or composite material.

21. Implant according to one of claims 1 to 11, characterized in that the pressure-receiving containers (3, 4) of the hollow body (1) have the shape of a lower cylinder or prism, with a flat or slightly curved, mutually parallel or slightly inclined base - And cover plates are provided.

22. Implant according to one of claims 1 and 11, characterized in that it is designed to attach an implantation instrument.

23. Implant according to one of claims 1 to 22, characterized in that the surface of the implant is structured and / or coated.