DE102013005398B3 - Motion preserving spinal disk prosthesis implanted into intervertebral space between vertebral bodies of human spinal column, has foam core with pores, whose pore size from center of core is decreased continuously toward edges of core - Google Patents

Abstract

The prosthesis (1) has a foam core for surrounding a flexible jacket (3). The foam core is made of open-pore foam. Free volumes of the foam core is filled with clean-viscous liquid i.e. sodium chloride solution, or non-viscous liquid. The foam core is provided with pores of different sizes. The pore size from the center of the foam core is decreased continuously toward edges of the foam core. A base material is made of polyurethane or polycarbonate urethane. The non-viscous liquid is provided with shear rate-dependant properties.

Description

Background of the invention

The present invention relates to a disc prosthesis for implantation in the intervertebral space between adjacent vertebral bodies (disc space) of a human spine. In particular, the present invention relates to a movement-preserving disc according to the preamble of present claim 1, which can largely replace a damaged or degenerated natural disc in their functionality.

The spine in its complex structure consists of a large number of individual joints. In the anterior spine area, a single joint consists of adjacent vertebral bodies and the intervertebral disc. The vertebral bodies and the intervertebral disc are additionally connected via the anterior and posterior longitudinal ligaments (longitudinal ligament anterius or posterior). In the region of the posterior spine, the vertebrae are articulated via the facet joints. Other ligaments connecting the vertebral bones posteriorly are the ligamentum flavum, interspinous ligament, supraspinal ligament and intertransversal ligament. While the facet joints together with the posterior ligaments primarily contribute to the posterior stabilization, the intervertebral disc mainly serves as a joint and buffering element with shock-absorbing and spacing effect and at the same time for limiting relative movements (flexion, extension and rotation) between the neighboring vertebrae. It essentially consists of a nucleus pulposus (nucleus pulposus) and a fibrous ring (annulus fibrosus), whose outer fibers terminate the intervertebral space, also called the intervertebral disc space, in the radial direction. In the anterior and posterior areas of the intervertebral disc, the fibers of the fiber ring are superimposed by the fibers of the anterior longitudinal ligament and the posterior longitudinal ligament, respectively, whereby the individual fibers sometimes pass over several intervertebral disc compartments. In the cranial-caudal direction, an intervertebral disc space is closed by the adjacent vertebral bodies.

The essential properties and functions of the natural disc can best be recognized by considering the interaction with the adjacent vertebral bodies.

In an axial load, the cover plates of the vertebral bodies, d. H. the disc surfaces of the vertebral bodies, because the volume of the gelatinous contents of the nucleus pulposus is incompressible and the bulge of the annulus fibrosus is insufficient to provide the required displacement volume. Due to the compression, the trabeculae of the spongiosa lying in the vertebral body are loaded, which, like a truss structure, can absorb, forward and distribute the load.

It is impossible to determine a singular center of rotation. Depending on the direction of movement, the movement excursion and the applied or transmitted force, the center of rotation shifts constantly. In this case, all 6 degrees of freedom of the movement are utilized. The facet joints, the posterior ligaments and, in particular, the fiber ring with the attached longitudinal bands passively determine or control the constantly changing position of the center of rotation. The reasons for the indeterminacy of the rotation center of the natural disc can be seen in the fluid-like properties of the gelatinous core. Depending on the load (force and direction), the mass of the gelatinous core is displaceable and deformable, but incompressible and thus remains constant in its volume. Due to the thus given hydrostatic pressure distribution in the intervertebral disc results in constant flexion and extension loads a constant pressure distribution on the cover plates of the vertebral body. The incompressibility of the nucleus pulposus also ensures that the vertebral bodies can only approximate by the extent to which the cover plates compress and the fibrous ring bulges out.

The individual fibers of the fiber ring are anchored in the cover plates of the vertebral bodies. The fiber ring limits the amount of movement of the individual joint both in the axial direction by vertical fibers and in rotational movements by inclined fibers. Between the individual collagen fiber layers, which in principle can only absorb tensile forces, there are also cartilage cells, the z. B. can absorb pressure forces in flexion and extension movements. Fibers and cartilage ensure a gradual change in the range of motion: with small forces (low elongation of the annulus fibers), the range of motion is relatively large, with large forces (average elongation of the annulus fibers), the range of motion is correspondingly limited. If the fibers of the annulus are maximally stretched at very large forces, no movement in the individual joint is possible without damaging or destroying fibers or bones.

In the case of the fiber ring consisting of collagen fibers and cartilage, the individual fiber layers are tightly packed in the outer area in order to prevent leakage of the gelatinous core, while they are no longer so close together in the inner area and already absorb material from the gelatinous core between their individual lamellar layers. The Fiber rings can be considered compressible while the gel core is made of incompressible material. In the transition region between the fiber ring and the gelatinous core, there is no clear border, the transition from the gelatinous core of the intervertebral disc to the marginal layers of the fiber ring is fluid.

State of the art

Previously known from the prior art artificial disc prostheses for complete replacement of an surgically removed disc, the demonstrated properties and functions of the natural disc can only partially or only insufficiently replicate. In general, one can distinguish two rough directions of development. While one is based on a mechanical design concept that initially only intends to restore the pure range of motion of a single element, the other focus is primarily on recreating the physiological-biomechanical properties of the natural nucleus around the elastic, shock-absorbing, and movable properties of the single joint replicate. Also hybrid artificial discs, which use both concepts, are already known.

In the mechanical design concept, two general types can be distinguished: discs of the ball and cup type and spring band discs. Spherical and pan type intervertebral discs usually include two metallic plate members connectable to the vertebral body cover plates with cooperating inner ball and socket portions which permit articulation movement of the plate members during spinal movement.

So is out of the EP 0 747 025 A1 an artificial intervertebral disc of the ball and pan type known that allows unlimited rotation and flexion and extension movements. The WO 2008/094260 A2 discloses an artificial disc of the same type with motion-limiting and shock-absorbing properties. From the WO 2010/034496 A1 a kit for such an artificial disc is removable, which allows a maximum rotational angle adjustment. From the US 2011/0054617 A1 For example, there is known a ball and socket type artificial disc having a shock absorbing property which has a ring surrounding the ball to maintain articulation movement of the ball within certain limits. One from the DE 60 2004 004 030 T2 known artificial disc prosthesis of the same type displays "floating", self-adjusting bearing means to simulate the non-stationary rotation point of the natural disc. One with the US 2011/0082556 A1 claimed artificial disc of the same type reveals an asymmetric, deviating from a spherical core with a resulting better adjustment due to variable height settings of their surfaces to be joined.

Mechanical spring band discs also have two metal end plates to be connected to the cover plates of the vertebral bodies. Between these are usually one or more spring means in the form of an elastic plastic pad or in the form of spiral, plate or leaf springs. The spring means defines a cumulative spring rate that is configured to maintain the spaced apart arrangement of adjacent vertebrae while permitting normal movement of the vertebrae during flexion or extension of the spine in any direction.

The EP 0 706 354 B1 discloses such a spring band disc with a lying between the cover plates plastic cushion made of silicone or a product of the family of polyolefins. From the EP 1 273 276 B1 is a spring band disc with spring means of a memory metal alloy known that has super-elastic properties at body temperature. The individual, consisting of screw, plate or leaf springs spring means are also located between the cover plates and are surrounded by a cylindrical protective sheath made of soft permanently elastic and biocompatible plastic. At one with the DE 10 2006 045 108 A1 claimed artificial disc prosthesis same type are in addition to the provided between the cover plates coil springs even as the cover plates surface parallel formed sheet formed from extending in the plane of these fabrics tensioned wires to record high axial loads with low material stress at low axial height can , Coil springs and wires are also made of memory metal alloys.

In addition to the above-mentioned artificial discs of the mechanical type, so-called hybrid discs already exist, which more and more incorporate the physiological-biomechanical properties of the natural disc based on the mechanical concept of purely maintaining freedom of movement, particularly with regard to shock absorption and movement limitation.

By way of example, only the WO 2008/073064 A1 , the US 2003/0191534 A1 and the US 6,966,931 B2 called. From the WO 2008/073064 A1 is an artificial disc of the ball and socket type known, the pivot bearing of an elastic Membrane is surrounded and between these and the cover plates, a viscous polymer, eg. Polyethylene or high molecular weight silicone. The US 2003/0191534 A1 discloses a hybrid disc having a ball and socket joint formed by a ring of viscoelastic material, e.g. B. biocompatible elastomer is surrounded. From the US 6,966,931 B2 For example, an intervertebral nucleus composed of an inner cushion (daughter sac) and a surrounding sheath (mother bladder), which is rotatably supported between two cover plates, is known, wherein the inner cushion is made of a softer material consisting of a gel, a foam or an elastomer low density, while the surrounding sheath is made of a higher density polyurethane to stabilize the intervertebral disc.

Although the mechanical and hybrid type artificial disc prostheses mentioned so far can provide mobility, shock-absorbing buffering and movement limitations, they all have rigid, mostly metallic cover surfaces. These significantly change the overall stiffness of the vertebral end plates and reduce the impact-buffering effect of the single joint. From a biomechanical point of view, a negative influence on other, healthy intervertebral discs is thus exerted in such a way that long-term problems in other individual joints of the spine can occur, as they are known from the fusion treatment ago. Also shock absorbing pads on the metallic top surfaces have not created a sufficient remedy.

To overcome this deficiency intervertebral disc prostheses have been developed, which in addition to an elastic core also continuously flexible or elastic top surfaces and at the same time have a mobility of 6 degrees of freedom rotation-limiting properties and sufficient spacing strength. These disc prostheses predominantly model the physiological-biomechanical properties in the core and edge area of a natural disc and make use of form-elastic and incompressible fluidic materials.

Such discs are for example from the US 4,863,477 , of the US 4,932,969 , of the DE 10 2008 042 401 A1 and the US 2007/0276492 A1 known.

The from the US 4,863,477 known flexible disc prosthesis consists of an upper and a lower half of non-porous rubber rubber or silicone rubber, which together form a cavity, which with a Fluigkeit, z. B. saline solution is filled. At the contact points to the vertebral bodies are small suction cups for connection. From the US 4,932,969 For example, an endoprosthesis made of an elastically compressible material having internal cavities filled with a non-compressible fluid such as sodium chloride solution (e.g., NaCl 0.9%) or silicone oil is known. The cavities are interconnected, resulting in a pressure equalization under load due to the fluid filling. The cover plates each consist of a flexible wire mesh. In the elastic body of the prosthesis, a reinforcing ring is incorporated to prevent excessive expansion. From the DE 10 2008 042 401 A1 a disc prosthesis is known, which essentially comprises a carrier component and an elastic shaped body as a core, which is completely or partially covered with a matrix layer. The core consists of a solid or hollow body made of an elastic biocompatible material. As a solid body, it preferably consists of silicone rubber, as a hollow body it has one or more cavities filled with one or more fluids (gel, NaCl). The carrier component serves the dimensional stability and the radial stiffening and preferably consists of a wire mesh of a biocompatible, non-absorbable material such as titanium or Nitinol or a relatively stiff sheet metal ring with openings or open porosity. In addition, a plasmachemic coating of the carrier component with simple organic molecules such as allylamine is provided in order to achieve a faster and better integration of the carrier element into the cell cultures of the vertebral endplates. The matrix layer located around the core serves to connect tissue cells to the core, in which case the biocompatible elastomeric matrix layer preferably has an open porosity which is filled with tissue cells, preferably cartilage cells, before insertion of the intervertebral disk in the context of in vitro cell cultivation. From the US 2007/0276492 A1 discloses a polyurethane-based disc prosthesis which consists of an upper and lower end plate and an intermediate nucleus region and a completely or partially surrounding Anulusregion. The material of the annulus region has anisotropic properties with respect to its modulus of elasticity. With further distance from the nucleus, the modulus of elasticity increases, so that the deformability of the intervertebral disc prosthesis decreases towards the edge, as it almost corresponds to the described properties of the natural disc.

Task and solution

Although each of the above artificial disc prostheses solves some of the problems associated with the replacement of motion preserving disc prostheses, each of the prostheses still has disadvantages. So, for example, comes from the US 2007/0276492 A1 Although known disc prosthesis, the elastic behavior of the natural disc while the next, but it leaves the fluid properties of the interior of the natural disc located gelatinous mass and thus their important function of a pressure distribution, ignored. Accordingly, there continues to be a need for an improvement of disc prostheses.

It is therefore an object of the present invention to provide an artificial motion-preserving intervertebral disc prosthesis, which largely corresponds in behavior and its operation to a natural human intervertebral disc.

This object is achieved by the features of the movement-preserving intervertebral disc according to the present patent claim 1. Advantageous embodiments and further developments of the claimed with the patent claim 1 disc prosthesis are given in the dependent claims 2 to 14.

Advantages of the invention

The claimed with claim 1 motion-preserving intervertebral disc is characterized in that it is in addition to a mobility of its center of rotation of 6 degrees of freedom in particular able to provide a power flow between the vertebral bodies, the constant, uniform as possible pressure distribution even in flexion and Extension positions of the spine ensured. At the same time it has shock-absorbing and movement-limiting properties and allows a natural disc adapted elasticity distribution. It has flexible, mitfedernde deck surfaces and is there also able to compensate for locally occurring loads due to local compliances due to fluid movements. It consists of a few different materials and can be implanted without major customization.

The further developments of the foam core of the subject matter listed in claims 2 to 6 each show advantageous embodiments which give a better simulation of the deformation properties of the natural intervertebral disc.

The development according to claim 7 allows a good anchoring of the intervertebral disc prosthesis with the cover plates of the vertebral body, promotes the growth of the vertebral end plates and at the same time ensures the preservation of the flexibility of the shell.

The development according to claim 8 stiffened in an advantageous manner the intervertebral disc prosthesis, so that their radial bulge and rotation is inhibited.

The advantageous embodiment according to claim 9 allows a simple and independent of the choice of material of the foam core separate production of the shell.

The embodiment according to claim 10 optimizes the behavior of the fiber-reinforced fabric in terms of shock-absorbing and rotation-inhibiting properties.

The material selections recited in claims 11 and 12 each show materials already used and proven in intervertebral disc prostheses that can be used to advantage in the invention. The manufacturing methods listed in claims 13 and 14 are particularly suitable for forming the pores of the claimed motion-preserving intervertebral disc prostheses and allow a one-piece production of foam core ( 2 ) and coat ( 3 ) in one operation.

embodiments

Embodiments of the invention, which disclose further advantages, are disclosed in FIGS 1 to 7 and will be described in more detail below.

Show it:

1a external shape of a disc prosthesis manufactured according to the invention by the centrifugal method

1b vertical section AA through the intervertebral disc prosthesis 1a

1c horizontal section BB through the intervertebral disc prosthesis 1a

2a outer shape of a manufactured according to the 3D printing process disc prosthesis according to the invention

2 B vertical section AA through the intervertebral disc prosthesis 2a

2c horizontal section BB through the intervertebral disc prosthesis 2a

3a outer shape of a disc prosthesis according to the invention with a chamber structure of the foam core

3b vertical section AA through the intervertebral disc prosthesis 3a

3c horizontal section BB through the intervertebral disc prosthesis 3a

4a outer shape of a disc prosthesis according to the invention with a layer structure of the foam core

4b vertical section AA through the intervertebral disc prosthesis 4a With 5 horizontally superimposed thin layers

4c vertical section AA through the intervertebral disc prosthesis 4a With 3 horizontally superimposed thicker layers

4d vertical section AA through the intervertebral disc prosthesis 4a with horizontally and vertically arranged layers

4e vertical section AA through the intervertebral disc prosthesis 4a with a further arrangement of the layer structure

5a outer shape of an intervertebral disc prosthesis according to the invention with anchoring elements distributed on the cover plates

5b another view of the intervertebral disc prosthesis 5a with view on both cover plates and marked detail A for the detailed representation in 5c

5c enlarged detailed representation of the surface structure of the intervertebral disc prosthesis 5b in the area of anchoring elements

6a outer shape of a disc prosthesis according to the invention according to the invention with a surrounding tire

6b vertical section AA through the intervertebral disc prosthesis 6a with completely closed coat and surrounding tires

6c vertical section AA through the intervertebral disc prosthesis 6a with broken coat and surrounding tires

7a Position of an intervertebral disc according to the invention in the intervertebral region and drawn section A for the detailed representation in FIG 7b

7b enlarged detail of the connection between a cover plate of the disc prosthesis and an end plate of a vortex in the region of the anchoring elements

A movement-preserving intervertebral disc prosthesis according to the invention 1 serves as a replacement for the natural disc, completely removing it so that it preserves the motion preserving disc prosthesis 1 can be used in the vacant space and takes over the function of the natural disc. 1a shows an adapted to the natural disc outer shape of a disc prosthesis according to the invention 1 with slightly curved cover plate 20 and coat 3 , which can be produced by centrifugal processes. As 1b in vertical section AA and 1c in horizontal section BB show, there is the motion-preserving disc prosthesis 1 from a foam core 2 and a completely surrounding flexible sheath 3 where both the foam core 2 as well as the coat 3 made of the same biocompatible, but not bioresorbable base material 4 which has been partially and / or gradually subjected to different processing. The foam core 2 becomes of open-pored foam 5 formed, the free volumes are filled with one or more different pure viscous or non-Newtonian liquids, wherein the foam core 2 pore 7 contains different size, each with a specific local distribution within the foam core 2 to obey.

The pores 7 of open-pored foam 2 stand through small openings 6 so interconnected that between the pores 7 a fluid compensation can take place. Furthermore, the free volumes of open-cell foam 5 completely or partially filled with liquid. The open-pored foam 5 primarily serves not the elastic damping by deformation under force, but by the arrangement and size of the individual pores 7 it influences the flow behavior of the fluid that is in the pores 7 located. In the case of a change in position of a single joint (cf. 7a , Whirl 21 , Intervertebral disc or intervertebral disc prosthesis 1 , Whirl 21 ) are the movements in the peripheral areas of the joint largest, in the middle, the amount of movement is less large. In a change of position in the sense of a flexion, the disc prosthesis 1 Ventrally compressed and stretched dorsally. The in the pores 7 The fluid present ventrally avoids the forces acting to flow into the space that results dorsally. The flow rate of the liquid depends on the fluidity, the size of the pores 7 and the size of the connections between the pores 7 from.

From the sectional views 1b and 1c The local distribution of the pores is recognizable, with the pore size from the center of the foam core 2 decreases towards its edges. The open-pored foam 5 fills the entire volume of the foam core 2 without being divided by dividing walls or the like into different areas. The arrangement of the pores 7 is changing continuously, z. For example, ventrally and dorsally are more likely to have small pores 7 , in the Center of the intervertebral disc prosthesis 1 big pores 7 , The transition between small and large pores 7 is fluent. This open-pored foam 5 is from a coat 3 enclosed, without a partition between foam 5 and coat 3 is available. This is achieved by already forming the foam 5 forms a shell around the foam. 1b also shows the slightly curved cover plate 20 attached to the end plate 19 , please refer 7 , the vortex 21 is adjusted.

The coat 3 can also be produced in an injection molding process, for. B. polyurethane. For this purpose, an injection mold is used, which corresponds to the outer dimensions of the intervertebral disc prosthesis 1 equivalent. Before that becomes the foam core 2 corresponding body of the same material, eg. As a polyurethane balloon, placed in the mold, which serves as a placeholder for the later einzufüllenden foam 5 serves. This body or polyurethane balloon can after hardening of the coat 3 from the spray-formed coat 3 are removed so that a cavity remains in this. Alternatively, the polyurethane balloon with the coat 3 to merge into a complete shape with a hollow interior. In the sprayed coat 3 For example, a filler neck can be integrated in the form of a hole to remove the polyurethane balloon and fill the foam 5 can serve. Will the foam 5 in the space for the foam core 2 filled, the intervertebral disc prosthesis 1 z. B. in a centrifuge rotated. Through this rotation, the desired distribution of the pores 7 in the intervertebral disc prosthesis 1 achieved during foaming. The small, heavy pores 7 crowd outward, the larger, lighter pores 7 remain rather central in the intervertebral disc prosthesis 1 , The amount of foam formulation can be determined by the expansion behavior and the size of the space for the foam core 2 in the sprayed coat 3 be determined beforehand. From the filler neck occur too large amounts at full expansion or puffing of the foam 5 out. In the hardened foam core 2 can through the filler neck of the jacket 3 a liquid, e.g. B. physiological NaCl solution 0.9%, are filled. To complete as much as possible displacement of any compressible gases in the foam core 2 to achieve the semi-finished disc prosthesis 1 placed on a shaker plate and the liquid slowly filled so that all gas escapes. Finally, the filler neck is plugged, with a vulcanization or welding process being preferred.

The flow rate of the liquid depends on its fluidity, the size of the pores 7 and the connection of these with each other. Also determine the forces occurring in the spine, as they are from the vortex 21 (see. 7 ,) over its end plate 19 on the cover plate 20 the intervertebral disc prosthesis 1 act, with the elastic coat 3 a deformation of the foam core 2 allows, the flow rate. With a flexion of the vertebrae 21 to each other are the movement rashes in the edge regions of the intervertebral disc prosthesis 1 the biggest.

2a shows an outer shape of a manufactured according to the 3D printing process disc prosthesis 1 according to the invention. Clearly visible are the curved cover plate 20 and the coat 3 , The 2 B and 2c show a vertical AA cut and a horizontal BB cut through the motion preserving disc prosthesis 1 to 2a , By means of the known 3D printing method, the open-pored foam 5 produced, in turn, the central pores 7 are formed larger, like the pores 7 on the smooth edge to the coat 3 out. Also recognizable are the more regular structures of the printed pores due to this production process 7 , Due to this manufacturing process results in a clean interface between foam 5 and coat 3 , foam 5 and coat 3 may consist of the same or of different material or material in this embodiment. Again, is in 2 B , analogous to 1b , shown that the domed cover plate 20 the end plate 19 of the vortex 21 is adjusted.

Another embodiment of the movement-preserving intervertebral disc prosthesis 1 according to the invention show the 3a to 3c , with the core in different areas (chambers) 10 is divided. 3a represents the outer shape of the motion-preserving disc prosthesis 1 represents, 3b and 3c in each case a vertical AA section and a horizontal BB section through the motion-preserving intervertebral disc prosthesis 1 , In both sections are areas 10 with Baumring-like partitions 9 recognizable in which foam 5 is introduced. Per area 10 are the properties of the foam 5 same, from area to area can change the properties of the foam 5 vary between constant or gradually varying porosity. The size of the pores 7 each takes from an inner area 10 to an outer area 10 from. The different foams 5 be in the coat 3 each through filler neck in the areas 10 introduced. All areas 10 are either with the same fluid or each area 10 is filled with different fluid, these having different fluidities. The number of areas 10 may vary. Their number is, however, preferably between 2 and 4.

4a shows the outer shape of a movement-preserving disc prosthesis 1 according to the invention with a layer structure of the foam core 2 , where in the vertical sections AA 4b to 4e different embodiments of Layer structure of the foam core 2 are shown. So shows 4b thin, mat-like layers 11 of the foam 5 , wherein the vertically seen, middle layer larger pores 7 owns, like the next layer above and below it 11 , These layers 11 turn, in turn, have larger pores 7 like the next layers attached to it 11 , All layers 11 be of an extra coat 3 enclosed. 4c shows only three layers 11 , wherein the middle layer 11 again larger pores 7 as the layer above and below it 11 , 4d shows a horizontal layer structure like 4b , There are also two lateral, annular layers 11 , wherein the inner layer 11 larger pores 7 has, as the outer annular layer 11 , 4e shows a middle layer 11 with big pores 7 , the "boxy" of a second layer 11 with smaller pores 7 is enclosed. This second layer 11 in turn is of a third layer 11 with even smaller pores 7 also surrounded "box-like". Common to all figures is the drawn horizontal joint line 8th , which is a two-part coat 3 disclosed.

5a shows the outer shape of a disc prosthesis according to the invention 1 with on the cover plates 20 distributed arranged anchoring elements 14 , The internal structure of the movement-preserving intervertebral disc prosthesis 1 is not relevant in the following description. Recognizable are on the cover plate 20 tree-ring-shaped structures 13 with embedded anchoring elements 14 from interspersed hydroxyapatite particles (HA) and / or titanium particles in a firm, positive connection with the cover plate 20 , These hydroxyapatite particles (HA) and / or titanium particles have a beneficial association with the endplate 19 of the vortex 21 a (cf. 7b ). It is also a point or strip-shaped arrangement of the hydroxyapatite (HA) and / or titanium particles possible; one the cover plate 20 continuous and fully covering arrangement is to be avoided, however, because they due to the elasticity of the cover plates 20 tends to breaks. 5b shows the disc prosthesis 1 to 5a in another view, in which both cover plates 20 are recognizable. Also shown is a section A for the enlarged detail drawing 5c for clearer identification of the surface structure in the anchoring area. Especially the detail A in 5c the arrangement of the hydroxyapatite particles (HA) and / or titanium particles, which firmly in the cover plate 20 are introduced and in turn in the end plate 19 clawing into it, resulting in a very strong, lasting connection. Due to the thermoplastic properties of polyurethane, the surface can be 12 the cover plate 20 be subjected to a heat treatment. This is z. B. a template made of a metallic material used, the areas on the cover plate 20 covers, which should be subjected to any heat treatment. Or the heating element itself has a mask, which in the 5a having shown rings. In the heated and thus liquid surface 12 the cover plate 20 Hydroxylapatitpartikeln (HA) and / or titanium particles are interspersed, which undergo a solid, positive connection with the polyurethane after cooling. The polyurethane is not known to have osteoconductive properties. From clinical applications of disc prostheses 1 with rigid, metallic cover plates 20 however, it is known that these are good at endplates 19 the vortex 21 grow when the bone-side surfaces 12 of the prostheses cover plates 20 with hydroxyapatite particles (HA) and / or titanium particles as anchoring elements 14 are coated.

6a shows the outer shape of a disc prosthesis according to the invention 1 with a surrounding tire 15 , Again, the disc prosthesis 1 have any of the shapes and properties described above. The mature 15 is for maintaining the shape of the disc prosthesis 1 advantageous. After vertical section AA the 6b the tire surrounds 15 the completely closed jacket 3 in the form of a ring. But it also makes sense, as in 6c shown the coat 3 to interrupt, so the tire 15 partly with the foam 5 comes into contact with the jacket 3 an annular cutout 17 owns and so does the tire 15 bridged this section. Also, the tire can 15 made of a fiber-reinforced fabric 16 exist, the z. B. consists of a network of crossed fabric fibers, with the coat 3 are permanently connected.

7a shows the position of the movement-preserving intervertebral disc prosthesis according to the invention 1 implanted in an intervertebral space between the vertebrae 21 , where the individual joint is in the undeflected state. The in 7a drawn section A is in an enlarged detail in 7b played. It illustrates the connection between a cover plate 20 an intervertebral disc prosthesis according to the invention 1 and an end plate 19 of the vortex 21 in the area of anchoring elements 14 , Clearly visible are the interspersed hydroxylapatite and / or titanium particles, which serve for better anchoring and accelerate the growth.

A further embodiment of the invention is that the base material 4 Polyurethane or polycarbonate urethane.

It is also advantageous if the purely viscous liquid is a sodium chloride solution and the non-Newtonian fluids have shear rate-dependent properties, since the very good suitability of these materials has already been demonstrated in intervertebral disc prostheses of the present type.

LIST OF REFERENCE NUMBERS

1

Disc prosthesis

2

foam core

3

coat

4

base material

5

foam

6

small openings between the pores

7

pore

8th

joint line

9

partitions

10

areas

11

layers

12

facing surfaces of the jacket to adjacent vertebrae bodies 3 , also cover plates 20 called

13

tree ring-shaped structure

14

anchoring elements

15

tires

16

fiber reinforced fabric

17

neckline

19

endplate

20

cover plates

21

whirl

Claims (14)

Movement-preserving disc prosthesis ( 1 ), at least consisting of a foam core ( 2 ) and a completely surrounding flexible sheath ( 3 ), where - both the foam core ( 2 ) as well as the coat ( 3 ) made of biocompatible, but not bioresorbable base material ( 4 ), which is partially and / or gradually subject to a different processing, - the foam core ( 2 ) made of open-pored foam ( 5 ), the free volumes of which are filled with one or more different pure viscous or non-Newtonian liquids, and - the foam core ( 2 ) Pores ( 7 ) of different size whose pore size is from the center of the foam core ( 2 ) decreases to its edges continuously or in stages. Movement-preserving disc prosthesis ( 1 ) according to the present claim 1, characterized in that - the foam core ( 2 ) by liquid impermeable partitions ( 9 ) with a tree-like profile in horizontal section, in different areas ( 10 ), each with open-pore foam ( 5 ) of different pore size are filled so that the size of the pores from the center of the foam core ( 2 ) to the coat ( 3 ) decrease. Movement-preserving disc prosthesis ( 1 ) according to claim 2, characterized in that - the individual areas ( 10 ) are filled with a liquid of the same or different fluidity. Movement-preserving disc prosthesis ( 1 ) according to the present claim 1, characterized in that - the foam core ( 2 ) from layers ( 11 ) open-pored foam ( 5 ) of different pore size. Movement-preserving disc prosthesis ( 1 ) according to the present claim 4, characterized in that - the layers ( 11 ) lie against each other in such a way that the layer ( 11 ) with the largest pores ( 7 ) in the middle of the foam core ( 2 ) lies. Movement-preserving disc prosthesis ( 1 ) according to one of the preceding claims 1 to 5, characterized in that - the surfaces facing the adjacent vertebral bodies ( 12 ) of the jacket ( 3 ) point or strip-shaped structures ( 13 ) with embedded anchoring elements ( 14 ) of interspersed hydroxyapatite particles and / or titanium particles in a firm, positive connection with the jacket ( 3 ) exhibit. Movement-preserving disc prosthesis ( 1 ) according to claim 6, characterized in that the structures ( 13 ) are tree-ring-shaped. Movement-preserving disc prosthesis ( 1 ) according to one of the preceding claims 1 to 7, characterized in that - the jacket ( 3 ) additionally from a tire ( 15 ) made of fiber-reinforced tissue ( 16 ) is surrounded. Movement-preserving disc prosthesis ( 1 ) according to one of the preceding claims 1 to 8, characterized in that - the jacket ( 3 ) an annular cutout ( 17 ) provided by a tire ( 15 ) made of fiber-reinforced tissue ( 16 ) is bridged. Movement-preserving disc prosthesis ( 1 ) according to one of claims 8 or 9, characterized in that - the fiber-reinforced fabric ( 16 ) consists of a network of crossed fabric fibers and with the jacket ( 3 ) is permanently connected. Movement-preserving disc prosthesis ( 1 ) according to one of the preceding claims 1 to 10, characterized in that - the base material ( 4 ) Is polyurethane or polycarbonate urethane. Movement-preserving disc prosthesis ( 1 ) according to one of the preceding claims 1 to 11, characterized in that - the purely viscous liquid is a sodium chloride solution and - the non-Newtonian liquids have shear rate-dependent properties. Movement-preserving disc prosthesis ( 1 ) according to one of the preceding claims 1 to 12, characterized in that - the foam core ( 2 ) and the coat ( 3 ) are produced by the centrifuge method. Movement-preserving disc prosthesis ( 1 ) according to one of the preceding claims 1 to 12, characterized in that - the foam core ( 2 ) and the coat ( 3 ) are produced by the 3-D printing method.

Images