DE10253169A1 - Implant used in procedures for stiffening the vertebral column consists of a compression-resistant hollow body made from two open receptacles which are pressed apart with insertion of filler material - Google Patents

Abstract

Implant consists of a compression-resistant hollow body made from two open receptacles (3, 4) which are pressed apart with insertion of filler material or by insertion of a filler made from an elastomer (12) to expand the hollow body after it has been implanted. Preferred Features: The implant is fitted to a feed tube which is connected at one end to a device for producing the required filling pressure. An instrument for introducing the hollow body is attached to the hole (8) provided for connecting the feed tube. The filler material is made from a self-hardening material.

Description

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

The surgical stiffening of a Section of the spine is called spinal fusion. Not with conservative treatment measures influenceable pain, spinal cord or nerve root compression and malposition are indications for spondylodesis. Pain of all morbidly changed Spine structures out. In many cases are they based on an "instability" of the movement segment, caused by degenerative changes in the intervertebral disc and Intervertebral joints of the movement segment. For the development of spinal cord or nerve root compressions Narrowing of the spinal canal or the intervertebral holes is responsible. With the surgical intervention, the pathological changes eliminated and stability through the spine the spinal fusion restored.

Spinal fusion is bone or bone replacement material between two or more vertebral bodies (interbody spondylodesis) or via the posterior vertebrae of two or several vertebrae attached (dorsal spondylodesis). During For several months, this creates a bony bridge that connects the vertebrae thus eliminating the instability that causes pain. requirement for the ossification is that the section of the spine in question is immobilized until the bone bridge enough is firm.

Are part of a spinal fusion also the reduced vertical as a result of intervertebral disc narrowing distances between the vertebral bodies too normalize and eliminate axis deviations of the spine. Because alone already the enlargement of the vertical vertebral distance through instrumental "distraction" a strong de-compressing Effect both on the nervous structures and on the intervertebral joints distraction is always an integral part of the procedure.

Because with inter-corporeal spinal fusion always at least spinal discs are cleared, is the stability of the spine in everyone Restore case. This can e.g. B. from the patient flameproof bone chips happen. Because the resilience of such chips is often uncertain and their availability is limited, and also that caused by chip removal morbidity can be significant, one uses increasingly instead of autogenous bone chips Bone replacement materials and pressure-resistant intervertebral implants (also called cages).

One can use intervertebral implants in all areas of the spine insert from the front (ALIF = anterior lumbar interbody fusion); on the lumbar spine about that also from behind (PLIF = posterior lumbar interbody fusion), from the side or from the side rear. Per disc space one or two implants inserted. If two implants from behind through two separate openings of the intervertebral disc ring, one speaks of a biportal Implantation. With a uniportal implantation, the intervertebral disc ring only opened at one point.

An intervertebral implant works as a pressure-absorbing placeholder that stabilizes spinal fusion, the adjustment of the vertebrae to each other secures and guarantees that between the vertebrae form a solid bone bridge can. Filled in the implants and / or bone or bone substitute material deposited around them forms the matrix for the new bone formation. For The stability of spinal fusion plays a crucial role in the ossification process Role. Movements within the spinal fusion delay or prevent their bony consolidation. For the additional Stabilization of the spondylodesis becomes pedicle systems or translaminar screw connections used.

The distraction has in addition to the therapeutic also a mechanical meaning: the associated elongation the soft tissue generates a force that the intervertebral implants between the vertebral bodies jammed. This prevents movements within the spinal fusion and diminishes above there is also the risk of secondary implant dislocation, which can be serious.

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

The invention has for its object to create an elastic intervertebral implant, around the bony Promote the development of spinal fusion, by both reducing the voltage differences occurring in the contact zone of the bone as well as new bone formation due to the elasticity or reduction stress shielding is stimulated. The implant should go over it also an expansion of the vertical vertebral body distance cause.

According to the invention, this is achieved in that the implant is formed from a hollow body filled with elastomer and this hollow body from at least two nested and in the body longitudinal axis against each other telescopically movable parts.

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. Among the thousandfold daily changes in stress Therefore, stress peaks occur in the contact zone of the bone, 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, ie pseudarthrosis can occur. This is tantamount to treatment failure.

The process described is reinforced if a priori spinal fusion is not entirely stable, i.e. if from the beginning movements between the vertebral bodies and the implant are possible. If the vertebral body z. B. with backward tilt The tension in the bone drops something that can move away from the implant to zero. Because in such a case the voltages of Can rise from zero to the maximum, will be the for the fatigue fractures responsible voltage differences are particularly large.

By the present invention now an elastic hollow body (HK) created to restore spine (WS) stability, which is part of interbody spondylodesis between the vertebral bodies in the intervertebral disc space or in defects of the vertebral body column (WkS) can be used The hollow body consists of two box-like parts and is compatible with tissue Filled with elastomer. By approximation of elasticity of the implant to that of the bone can cause high changes in tension be avoided with cyclical loading in the contact zone of the bone with the implant and there to break down the Bone with subsequent instability. Bone graft ossification by approximation of elasticity of the implant to that of the bone is promoted and with it the success secured with an interbody spinal fusion.

In one embodiment variant, 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 one Elasticity, so that the elastomer never directly matches the surrounding area of the Implant comes into contact.

An execution provides that the elastomer is the hollow body completely or partially. It can thereby still possible variations created, among other things even with different areas different Elasticity. The elastomer should preferably completely cover the interior of the implant to complete, in order to avoid gas or liquid in each case during loading and unloading is pressed out of the implant or sucked into the implant.

In this context it is also possible, that that's in the hollow body filled Elastomer on the inner side walls of the hollow body loose or tight and tight.

If it is further provided that the inner surfaces the top and bottom wall of the box-like one inside the other Parts of the hollow body when loaded into the filled Penetrating elastomer can have a wide variety of forces and different Special force in the implanted state of the implant To be received.

In a further variant it is envisaged that under the filled elastomer, i.e. between Elastomer and the bottom wall of the box-like nested Parts of the hollow body a cavity is left. This can increase the elasticity of the implant increased even further become, or can additional Means of change or to increase of elasticity be used.

With a special version can be provided that a hermetically sealed in the elastomer Gas bubble is incorporated. This means a very simple and also structurally very effective design to increase the Elasticity.

In a special design variant suggested that on the hollow body a device e.g. is attached in the form of a clamping screw, around the hollow body compressed to a reduced height before the implantation to expand the implantation. This makes implantation easier and can about it also an enlargement the vertical vertebral distance Bring about (distraction). Also receives the intervertebral implant thereby preloading the implant in constant Maintains contact with the vertebral body and the harmful Voltage differences reduced.

For an optimal possibility a design is proposed for the insertion of the implant, where the outer part of the box-like hollow body a wedge-shaped Has insertion end. This can significantly improve the distracting effect become.

Is in a constructively simple manner depending on the particular one to be chosen Shape and depending on the specific application of the implant, that this is made of metal, polymer or a composite material are made.

It is also proposed that at manufacturing of polymer or composite radiological shadows incorporating elements or materials into the implants are. So that can the implants are 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, if the pressure-absorbing parts of the hollow body have the shape of a low cylinder or prism, with flat or slightly curved, mutually parallel or slightly inclined base and cover plates are provided.

So that the implant is also easier Can be implanted, it is suggested that this be used for Attaching an implantation instrument is formed. So that is on the implant itself for that ensured that a good grasping and insertion of the same is guaranteed is.

See an advantageous embodiment furthermore that the surface of the implant are structured and / or coated. This will add for one 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 particular advantages will appear in the description below based on the drawings explained. Show it:

1 a section of an intervertebral disc space with an inserted implant;

2 a section through an implant in a simplified representation;

3 and 4 Sections through an implant in the simplified representation, the compressed position and the expanded position being shown once;

5 and 6 Sections through an implant in a simplified representation, wherein the compressed position and the expanded position are shown and a hermetically sealed gas bubble is provided as an additional elastic element;

7 an oblique view of a particular embodiment of an implant.

According to the present invention, the implant is thus made with an elastomer 2 filled hollow body 1 executed, the hollow body 1 from at least two parts which are inserted into one another in a box-like manner and telescopically movable in the longitudinal axis of the body 3 and 4 consists. The elastomer 2 is filled into the inner part of the implant, this elastomer 2 the hollow body 1 completely or partially. The elastomer 2 lies on the inner side walls of the part 4 of the hollow body 1 loose or firm and sealing.

The inner surfaces of the top wall 6 and the bottom wall 5 Of the parts 3 and 4 of the implant are designed so that they load into the elastomer 2 can penetrate. To increase elasticity, either under the elastomer 2 , ie between elastomer 2 and the bottom wall 5 of the implant, a cavity can be left or it can be as in the design according to the 5 and 6 visible, a hermetically sealed gas bubble 7 in the elastomer 2 be incorporated.

A device is attached to the implant, e.g. B. in the form of a clamping screw 8th , which enables the implant compressed to a reduced height before the implantation only after the implantation, that is to say after the clamping screw has been loosened 8th , expands. So that the area of expansion cannot go too far, the end of the clamping screw grips 8th into a slot 9 a (see 7 ) so that the part is pushed out 4 from the part 3 of the hollow body 1 is limited to a certain level.

To increase the distracting effect mentioned, the outer part 3 of the implant has a wedge-shaped insertion end 10 exhibit.

Functionally, such an intervertebral implant with a wedge end consists of two parts. In 2 this is shown as an example. The two parts are the part 3 with the wedge-shaped insertion part 10 and the part 4 of the implant. The shape of the two parts depends on the area of the spine and the technique with which the implant is to be used.

The implant parts 3 have the following basic shape: It is a blunt wedge-shaped insertion end 10 which with its base steplessly on that side of the part 3 with which the implant is inserted into the intervertebral disc space. Top and bottom surface of the insertion end 10 are flat and inclined so 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-absorbing parts 3 and 4 can have the shape of a low cylinder or prism, with flat or slightly arched, parallel or slightly inclined base and cover plates. The implants can be a device for attaching an implantation instrument 11 point. The surfaces of the implants can be structured and / or coated.

The elastic intervertebral implants can consist of metal, polymer or composite material. To the location from radiologically invisible, from polymer or composite material manufactured implants in the body Making radiological shadows visible or materials incorporated into the implants.

In the context of the invention, it is possible to use the hollow body 1 from more than two box-like parts 3 and 4 to build. So it would be conceivable, for example the part 4 to form from several sub-areas that are separately elastic relative to the part 3 are movable. It would then also be possible to completely or partially fill the different partial areas with elastomers of different elasticity.

The following implantation technique has become possible with the implant according to the invention: After possibly expanding the intervertebral disc space or the defect with a ge suitable instrument (eg a pair of expanding pliers), the height of the vertical vertebral body distance is measured and the implant selected that can still be inserted into the intervertebral disc space in a compressed (reduced-height) state. 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 8th solved so that the implant can expand in the vertical direction.

With uniportal dorsal or dorsolateral application technique have to the implants during the Implantation from the initial sagittal or oblique direction of implantation be rotated in the frontal direction, especially if only one Implant is inserted into the intervertebral disc space. At the desired Jamming the implant can make it difficult to rotate prepare or impossible his.

The uniportal intervertebral implant essentially has the following devices and features: The implant has a bean shape (see in particular 7 ). The top and bottom surface of the implant part 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. The part 10 the opposite part of the implant 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 part 10 in the part 3 The upper and lower front edges of the implant are sharp. Against that part 10 the leading edges are gradually rounded towards the opposite end of the implant. On the top and bottom surface of the part 3 can against the part 10 incisions running parallel to the front edges are made, 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. Through a rod-shaped insertion instrument attached to its rear end, which also serves as a clamping screw 8th can work, the implant is initially steerable. 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 are fundamental in all areas of the spine applicable: on the cervical, thoracic and lumbar spine of in front, and on the lumbar spine additionally uni- or biportal from behind, from the side or from the side behind. requirement for the applicability is that the shape of the two implant parts both the anatomical conditions of the intended implantation site (region The spine) as well as the intended implantation technique is designed.

Instead of that in the elastomer 2 trained gas bubble 7 or else in addition to such an embodiment could be in a cavity between the lower wall 5 of the part 3 and the inserted and with elastomer 2 filled part 4 a further spring element can be provided to increase the elasticity of the entire implant. Here, for example, the use of a spring element in the form of a spiral, helical or leaf spring would be possible, or a further insert in the form of an elastomer could be provided, which may be compared to the elastomer 2 in part 4 has a different elasticity.

Because the elastomer 2 itself has the effect of a spring, it would in principle also be possible and to classify it 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 are used can be.

Claims (14)

Implant for use in stiffening operations on the spine, characterized in that the implant is made of an elastomer ( 2 ) filled hollow body ( 1 ) is formed and this hollow body ( 1 ) from at least two parts that are inserted into each other in a box-like manner and telescopically movable in the longitudinal axis of the body ( 3 . 4 ) consists. Implant according to claim 1, characterized in that the elastomer ( 2 ) in the inner part of the hollow body ( 1 ) is filled. Implant according to claim 1 or 2, characterized in that the elastomer ( 2 ) the hollow body ( 1 ) completely or partially. Implant according to one of claims 1 to 3, characterized in that the in the hollow body ( 1 ) filled elastomer ( 2 ) on the inner side walls of the hollow body ( 1 ) fits loosely or tightly and sealingly. Implant according to claim 1, characterized records that the inner surfaces of the top and bottom walls ( 6 . 5 ) of the nesting parts ( 3 . 4 ) of the hollow body ( 1 ) when loaded into the filled elastomer ( 2 ) penetrate. Implant according to claim 1, characterized in that under the filled elastomer ( 2 ), ie between the elastomer ( 2 ) and the lower wall ( 5 ) of the nesting parts ( 3 . 4 ) of the hollow body ( 1 ) a cavity is left. Implant according to claim 1, characterized in that in the elastomer ( 2 ) a hermetically sealed gas bubble ( 7 ) is incorporated. Implant according to claim 1 or one of the preceding claims, characterized in that on the hollow body ( 1 ) a device, e.g. in the form of a clamping screw ( 8th ) is attached to the hollow body compressed to a reduced height before implantation ( 1 ) to expand after the implantation. Implant according to claim 1 or one of the preceding claims, characterized in that the outer part ( 3 ) of the box-like hollow body ( 1 ) a wedge-shaped insertion end ( 10 ) having. Implant according to one of claims 1 to 9, characterized in that that this is made of metal, polymer or a composite material are made. Implant according to claim 10, characterized in that radiologically when manufacturing from polymer or composite Shading elements or materials are incorporated into the implants are. Implant according to one of claims 1 to 11, characterized in that the pressure-absorbing parts ( 3 . 4 ) of the hollow body ( 1 ) have the shape of a lower cylinder or prism, with flat or slightly curved, parallel to each other or slightly inclined base and cover plates are provided. Implant according to one of claims 1 to 11, characterized in that it is used to attach an implantation instrument ( 11 ) are trained. Implant according to one of claims 1 to 13, characterized in that that the surface of the Implants are structured and / or coated.