KR20050112108A - Vertebral disc or intervertebral disc prosthesis - Google Patents

Abstract

The invention relates to a vertebral disc or intervertebral disc prosthesis comprising: A) an upper apposition plate (1) that is suited for placing against the base plate of a vertebral body; B) a lower apposition plate (2), which is located at a distance from the upper apposition plate and which is suited for placing against the cover plate of a vertebral body; C) a number of elastic means (3) that are placed between both apposition plates (1, 2) in the peripheral areas (4) thereof so that both apposition plates (1, 2) can elastically move relative to one another, and; D) a central axis (5) that is essentially perpendicular to both apposition plates (1, 2). Said elastic means (3) are formed or arranged in such a manner that the vertebral disc has, by and large, an asymmetric rigidity.

Description

Vertebral discs or intervertebral disc prosthesis {VERTEBRAL DISC OR INTERVERTEBRAL DISC PROSTHESIS}

The present invention relates to an intervertebral disc prosthesis or intervertebral disc prosthesis according to claim 1.

Prostheses of this type can be formed as cell replacements, flexible cages or internal vertebral disc prostheses, which are insertable from the posterior (PLIF-technique). This prosthesis can be located between the vertebral bodies adjacent to the spinous process in the form of a dynamic implant.

U.S. Patent No. 5 458 642 (Inventor Bear, et al.) Discloses a vertebral disc prosthesis having an upper and lower plate in the form of kidneys connected to each other via a plurality of identical coil springs at the periphery (circulated about a central cell). It is. The coil springs are arranged at regular intervals relative to each other and allow three-dimensional movement of both plates within certain limits. A disadvantage of the above known vertebral disc prostheses is that the stiffness of the implant-evenly spaced from the center of the implant-is uniform in each radial direction, ie the implant has symmetric stiffness.

1 is a perspective view of a vertebral disc prosthesis.

Figure 2 is a side view of the vertebral disc prosthesis according to Figure 1;

Figure 3 is a plan view of the vertebral disc prosthesis according to Figure 1;

4A is a side view of another embodiment of a vertebral disc prosthesis.

FIG. 4B is a top view of the embodiment of the vertebral disc prosthesis shown in FIG. 4A without the upper coalescing plate. FIG.

4C is a perspective view of the vertebral disc prosthesis shown in FIG. 4A.

FIG. 4D is a perspective view of the vertebral disc prosthesis shown in FIGS. 4A-4C without an upper coalescing plate. FIG.

5A is a front view of another embodiment of an intervertebral disc prosthesis without an upper coalescing plate.

Fig. 5B is a plan view of the vertebral disc prosthesis shown in Fig. 5A.

5C is a side view of an embodiment of the vertebral disc prosthesis shown in FIGS. 5A and 5B.

5D is a perspective view of an embodiment of the vertebral disc prosthesis shown in FIGS. 5A-5C.

6A is a plan view of another embodiment of a vertebral disc prosthesis.

6B is a cross-sectional view along line B-B of the embodiment of the vertebral disc prosthesis shown in FIG. 6A.

FIG. 6C is a perspective view of a spring element in which the vertebral disc prosthesis without the upper coalescing plate shown in the embodiment of FIGS. 6A and 6B is connected with the lower coalescing plate.

6D is a perspective view of an embodiment of the vertebral disc prosthesis shown in FIGS. 6A-6C.

7A is a plan view of another embodiment of a vertebral disc prosthesis.

FIG. 7B is another cross-sectional view taken along line B-B of the intervertebral disc prosthesis shown in FIG. 7A.

7C is a side view of the vertebral disc prosthesis shown in FIGS. 7A and 7B.

7D is a perspective view of the vertebral disc prosthesis shown in FIGS. 7A-7C.

8 is a schematic representation of a vertebral disc prosthesis implanted between two vertebral bodies as shown in FIGS. 7A-7D.

FIG. 9 shows the vertebral body with two vertebral disc prostheses as shown in FIGS. 7A-7D laid parallel to the longitudinal axis of the spine on the cover plate.

FIG. 10 is a plan view of the anterior side of two vertebral disc prostheses implanted between two vertebral bodies as shown in FIGS. 7A-7D.

11 is a view of another embodiment of the elastic means of the intervertebral disc prosthesis according to the present invention.

(Example)

The intervertebral disc or intervertebral disc prosthesis shown in FIGS. 1 to 3 is adapted to be supported on a circular upper coalescing plate 1 suitable for being supported on the base plate of the vertebral body and a cover plate of the vertebral body having a gap therefrom. It consists of a circular lower coalescing plate (2) and two intermediate plates (6) which are likewise circularly formed between the two coalescing plates (1, 2), all plates at right angles along a common central axis (5). Are arranged.

A total of eight elastic means 3-in the form of rings 3a-3h-are arranged between the two circular coalescing plates 1, 2, which are arranged radially with respect to the central axis 5 and the annular shape thereof. The face lies perpendicular to the coalescing plates 1, 2.

In order for the vertebral disc prosthesis to be engaged, the upper alliance plate 1 is connected with the adjacent intermediate plate 6 via a total of eight screws 7, and the lower alliance plate is likewise adjacent with the total eight screws 7. Connected with (6). For this purpose, the coalescing plates 1, 2 comprise a corresponding bore 9 for accommodating the screw head and the intermediate plate 6 comprises a corresponding screw bore for accommodating the screw shank. The screws 7 are arranged to extend respectively between two adjacent rings.

The individual rings 3a to 3h are formed in diameter by the upper plate pairs 1 and 6 and the lower plate pairs 2 and 6, so that both plate pairs 1, 6 and 2 and 6 have rings 3a to 3h. Can be inclined with respect to each other-within any limit (compressibility of about 1.0 to 1.5 mm at the periphery) from parallelism without load due to the elasticity of the rings 3a to 3h . Thus, the two coalescing plates 1, 2 may have an angle of about 12 ° with respect to each other.

In order that the height of the intervertebral disc prosthesis is kept small, the coalescing plates 1 and 2 and the intermediate plate 6 have recesses corresponding to the profile of the rings 3a to 3h in the penetration region of the rings 3a to 3h. 8).

The elastic rings 3a to 3h arranged at the periphery at regular intervals of 45 ° have different elasticity and rigidity, which are different materials of the ring, different geometry of the ring or different profiles of the ring (filled form, hollow form, round form) , Orthogonal form). This provides a higher rigidity in the region where the rings 3f, 3g, 3h are provided in the region where the rings 3a, 3c, 3d are provided. Thus, in the region of the ring 3c when a predetermined force is applied perpendicularly to the coalescing plate 1, a smaller compressive force is formed than when applying the same force on the region of the ring 3g. This asymmetric property allows for improved physiological properties of the intervertebral disc prosthesis, where the rings 3f, 3g, 3h complementary to the rings 3b, 3c, 3d, when the spine is bent forward. Compression force is greater than if the spine is bent backwards.

The elastic ratio of the individual rings is preferably varied between 50% and 100%. As a value, the elastic ratio may be between 300N / mm and 1'000N / mm.

In the embodiment of FIGS. 4A-4D, the turn-shaped means 3 comprises a coil spring 10, the longitudinal axis 11 of which is circular in a plane perpendicular to the central axis 5. 10) surround the central axis 5 of this implant at an angle of 360 °. Here, the coil spring 10 is displaced outward in the circumferential direction of the circular coalescing plates 1 and 2, so that the coil spring slightly protrudes into the circumference of the coalescing plates 1 and 2. Coil spring 10 includes two circular portions with opposite slopes of the winding of the spring wire. At these two connection points the windings of the coil spring 10 are connected to each other via one loop 12, 13 each. The loops 12, 13 are arranged in the peripheral segment of the coil spring 1 towards the upper coalescing plate 1. By the structure of the coil spring 10 having two circular portions with opposite slopes, the torsional rigidity of the implant can be adjusted. On the inner surfaces of the coalescing plates 1, 2, which are opposed to each other, circular ridges 19, 20 concentric with the central axis 5 are arranged. Since the spring wire is wound through one bore of two circular ridges 19 and 20 for each winding, the coalescing plates 1 and 2 and the coil spring 10 can be held together. In addition, the spacing of the two loops 12, 13 provided between both windings of the spring wire adjacent to each other can be formed differently. Since the winding of the coil spring 10 has a uniform slope on the two circular portions of the coil spring 10, the spring constant of the implant has a different value at the connection point of the two circular portions. With this configuration of the two parts of the coil spring 10 having windings with opposite inclinations, the torsional rigidity of the implant is equal in both directions of rotation.

In the embodiment shown in Figs. 5A to 5D, the coalescing plates 1, 2 (only one coalescing plate 2 is shown) are formed in an elliptical shape, whereby the elliptical longitudinal axis 14 of the elastic means 3 is formed. It is distinguished from FIGS. 4A-4D by including four elliptical coil spring elements 15, 16, 17, 18 arranged on and separated from one another. The two coil spring elements 15, 16, 17, 18 placed opposite in the radial direction are formed mirror symmetrically with respect to each other, and the two coil spring elements 15, 16 arranged in mirror symmetry are opposite to each other. The other two coil spring elements 17, 18, which comprise a winding with an inclination and are arranged in mirror symmetry, each comprise a loop 12, 13 in the middle thereof so that the direction of rotation of the winding is changed. In addition, the inclination of the two pairs of coil spring elements 15, 16, 17, 18 arranged in mirror symmetry is displaced so that the spring constant of the elastic means 3 is supported on the outer surfaces of the two coalescing plates 1, 2 It may be different depending on the position of the axis of rotation between the vertebral bodies 34 and 35 (see Fig. 8).

In the embodiment of FIGS. 6A-6D, the structure of the elastic means 3 comprises spring elements 22, 23, the elastic means being concentric with respect to the central axis 5, the spring element being a plurality of meandering portions ( It differs from the embodiment shown in FIGS. 4 and 5 in that it comprises a spring wire 25 having serpentine. The spring elements 22, 23 have a torus, and the connecting piece extends at an angle with respect to the meridion of the torus between the loops 12, 13 of the meander 24. The angle between the connecting piece between the loops 12 and 13 of the meander 24 and the meridian of the torus has the same value in the opposite direction with respect to both spring elements 22 and 23. Each coalescing plate 1, 2 also includes two ridges 19 ′, 19 ″, 20 ′ 20 ″ concentric with the central axis 5. One loop 12 of the meander 24 is guided through two bores in the circular ridge 19 of the upper coalescing plate 1 similarly to the embodiment according to FIG. 4, while the meander 24. The other loop 13 of is guided through two bores in the circular ridge 20 of the lower coalescing plate 2, so that the two coalescing plates 1, 2 and the elastic means 3 can be held together. . Loops 12, 13 of inner spring element 22 are guided through bores in inner ridges 19 ′, 20 ′, and loops 12, 13 of outer spring element 23 are outer ridges 19. ”, 20”) through the bores.

7a to 7d are provided with upper and lower coalescing plates 1, 2 having an upper surface of a right angle form arranged transverse to the central axis 5. The longitudinal axes 11 of the two coil spring elements 15, 16 arranged in sequence between the coalescing plates 1, 2 are parallel to the elongate axes of the right angled coalescing plates 1, 2. The two coil spring elements 15, 16 have opposite slopes in their windings. In addition, the upper surfaces lying inside the two coalescing plates 1 and 2 are arranged with ridges 19 and 20 parallel to the long axis, and the ridge includes bores extending laterally with respect to the long axis. In this way, the windings of the coil spring elements 15, 16, which are guided through the bore, hold two coalescing plates 1, 2.

The use of the two vertebral disc prostheses shown in FIGS. 7A-7D are shown in FIGS. 8-10. The vertebral disc prosthesis is the intermediate vertebral space of the two adjacent vertebral bodies 34 and 35 side by side such that the coil spring elements 15 and 16 extend in the anteroposterior direction and each vertebral disc prosthesis is arranged transverse to the longitudinal axis of the vertebrae. Is inserted into. This arrangement of the vertebral disc prosthesis results in different elastic ratios of the elastic means 3 for elastic / extension and transverse bending of the spine.

In the embodiment of the elastic means 3 of FIG. 11, a spring wire 25 wound with a loop 26 is provided. The loop 26 of spring wire, on the one hand, is configured to close the loop 26 similarly to the ring shown in FIG. 1 and to form each spring element distributed between the coalescing plates 1, 2 in some form. . On the other hand, the loop 26 can form a winding of a spring element in the form of a coil spring, similar to the embodiment shown in FIG. Fixing the spring wire 25 to the coalescing plates 1, 2 is in accordance with one of the embodiments shown in FIGS. 1 to 10. Further, the structure of the coalescing plates 1 and 2 and the distribution of the elastic means 3 are in accordance with one of the embodiments shown in Figs.

To this end, the present invention provides a solution. It is an object of the present invention to provide an intervertebral disc prosthesis with asymmetric stiffness. This is an advantage in that the vertebral disc prosthesis can be structurally adjusted to its physiological properties, for example in the case of lateral extension of the vertebrae, providing greater stiffness of the implant than in lateral movement in the lateral anterior direction. Has

This object of the invention is achieved by a vertebral disc prosthesis having the features of claim 1.

The advantage achieved by the present invention is that in practice, the vertebral disc prosthesis according to the invention can achieve physiological properties even under load of the spine and in particular the rotation point of the implant can be adjusted by asymmetrical stiffness changes.

In a preferred embodiment, the number of elastic means is in the range of 4 to 12, preferably 6 to 10.

In other embodiments, the resilient means may be identical to one another, but are arranged in the peripheral region of the vertebral disc prosthesis irregularly in the radial direction. In this way, the rigidity of the vertebral disc prosthesis can be achieved by a variable number of identical elastic means for each angle of the periphery or, optionally, through an irregular (ie, dense or less compact) arrangement of the same elastic means. It can be selectively adjusted in production, and different stiffness of the vertebral disc prosthesis is formed along each radial direction, providing an advantage that more preferably corresponds to anatomical conditions than conventional vertebral disc prostheses.

In another embodiment, at least one portion of the resilient means is configured differently from one another, and the resilient means are preferably arranged in the peripheral region of the vertebral disc prosthesis, preferably in the radial direction.

In another embodiment, at least a portion of the resilient means is configured differently from one another, and the resilient means are arranged in the peripheral region of the vertebral disc prosthesis irregularly in the radial direction.

In another embodiment, the stiffness of the vertebral disc prosthesis is higher within at least some region of the 90 ° bow of the periphery and within the 90 ° bow of the complementary periphery.

In other embodiments, at least some of the elastic means are formed of various materials having different stiffness.

As the material, all known metals and polymer materials for implants are suitable. The implant may be provided with a HAC-coating layer.

Implant materials are titanium, nitinol, titanium alloys and steel.

-The combination of materials for coalescing plates is titanium / titanium alloy,

-The material combination for the intermediate plate is titanium / titanium alloy,

-Combination material for screw is titanium,

The material combination for the ring is nitinol, titanium or steel.

The geometry and top surface of the coalescing plate is preferably adapted to the natural endplate of the vertebral body, and in various embodiments, the two coalescing plates may be constructed in the form of round, right angled, kidney, oval or coiled. .

In another embodiment, the elastic means is formed as a ring or partial ring, and the arrangement of the ring faces of the elastic means thus formed is as follows.

The ring face intersects the central axis of the vertebral disc prosthesis.

The ring face does not intersect the central axis of the vertebral disc prosthesis.

The ring face extends substantially perpendicular to the two coalescing plates.

The ring face is oblique to two coalescing plates.

In other embodiments, at least some of the rings have different stiffness, and the arrangement of the rings is preferably done so that the stiffness continuously increases or decreases.

In another embodiment, the advantage is provided that the peripheral portion region has higher or lower stiffness because the ring is arranged at the periphery.

In various embodiments, the elastic means can be selected from the following group. Coil springs, elastic bellows, plastic cylinders, bands, wire knits, filament or plastic coated wire. As a result, the ring has the following advantages over the configuration of the elastic means.

Increased flexibility,

-Simpler production know-how,

-Simpler operation,

Viscoelastic properties of the vertebral disc prosthesis.

In another embodiment, the resilient means may consist of a wire, preferably formed as a single filament.

In another embodiment, the resilient means comprises a spring element having a spring wire configured as follows.

The spring wire comprises a serpentine and / or

The spring wire comprises at least one loop.

In another embodiment, the intervertebral disc prosthesis comprises a cell of synthetic resin. This achieves the advantage that the vertebral disc prosthesis has viscoelastic properties and provides improved damping during the movement of adjacent vertebral bodies.

In another embodiment, the compressibility of the vertebral disc prosthesis is at least 0.7 mm, preferably 1.0 mm and at most 1.2 mm, preferably at most 3.5 mm at the periphery.

The connection of the resilient means and the coalescing plate may be formed by shape engagement or interference fit.

In another embodiment, the two coalescing plates have an angle of 10 ° to 14 ° to each other.

In another embodiment, the resilient means can be assembled in one unit and on which two coalescing plates are slidable or snappable.

DETAILED DESCRIPTION OF THE INVENTION The present invention and improvements of the present invention are described in detail in the various embodiments with reference to the drawings schematically shown in part.

Claims (26)

(A) an upper coalescing plate (1) suitable for being supported on the base plate of the vertebral body, (B) a lower coalescing plate (2) spaced therefrom and adapted to be supported on the cover plate of the vertebral body, (C) a plurality of elastic means (3) arranged in the peripheral region between the two coalescing plates (1, 2) so that the two coalescing plates (1, 2) enable elastic movement with respect to each other, (D) A vertebral disc prosthesis or intervertebral disc prosthesis comprising a central axis 5 that is substantially vertical on two coalescing plates 1, 2, The elastic means (3) is a vertebral disc prosthesis, characterized in that the vertebral disc prosthesis is formed or arranged so as to have asymmetric rigidity as a whole. The vertebral disc prosthesis according to claim 1, characterized in that the number of elastic means (3) is in the range of 4 to 12, preferably 6 to 10. 3. The vertebral disc prosthesis according to claim 1, wherein the resilient means are identical to one another but are arranged irregularly in the peripheral region in the radial direction. 4. 3. The intervertebral disc prosthesis according to claim 1, wherein at least part of the resilient means is arranged differently and is arranged regularly in the peripheral region (4), preferably in the radial direction. 4. 3. The intervertebral disc prosthesis according to claim 1, wherein at least part of the resilient means is arranged in the peripheral region (4) differently and preferably irregularly in the radial direction. 4. The stiffness of the vertebral disc prosthesis is higher in at least a portion of the 90 ° bow of the periphery, within the 90 ° bow of the complementary periphery. Vertebral disc prosthesis. The vertebral disc prosthesis according to any one of the preceding claims, characterized in that at least part of the resilient means (3) is formed of various materials with different stiffness. The vertebral disc prosthesis according to any one of the preceding claims, characterized in that the two coalescing plates (1, 2) are formed in a circular shape. The intervertebral disc prosthesis according to claim 1, wherein the elastic means is formed of a ring or a partial ring. 10. A vertebral disc prosthesis according to claim 9, characterized in that the ring face of the elastic means (3) formed of a ring or partial ring intersects the central axis (5). 10. The vertebral disc prosthesis according to claim 9, characterized in that the ring face of the resilient means (3) formed of a ring or partial ring does not intersect the central axis (5). 12. A vertebral disc prosthesis according to any one of claims 9 to 11, characterized in that the ring face extends substantially perpendicular to the two coalescing plates (1, 2). 12. The vertebral disc prosthesis according to any one of claims 9 to 11, characterized in that the ring face extends at an angle with respect to the two coalescing plates (1, 2). 14. The intervertebral disc prosthesis according to any one of claims 9 to 13, characterized in that at least a portion of the ring has a different stiffness and is preferably arranged in a stiffness that increases or decreases continuously. 15. The vertebral disc prosthesis according to claim 14, wherein the ring is arranged at the periphery. The intervertebral disc prosthesis according to claim 1, wherein the elastic means 3 is selected from the group of coil springs, elastic bellows, plastic cylinders, bands, wire knits, filaments or plastic coated wires. . The intervertebral disc prosthesis according to any of the preceding claims, characterized in that the elastic means (3) consists of a wire, preferably formed as a single filament. The intervertebral disc according to any one of the preceding claims, characterized in that the resilient means (3) comprises at least one spring element (22, 23) consisting of a spring wire with a sandpaper (24). Prosthesis. The elastic means (3) according to any one of the preceding claims, wherein the elastic means (3) comprises at least one spring element (22, 23) consisting of a spring wire (25) comprising at least one loop (26). Lumbar disc prosthesis, characterized in that. 20. The vertebral disc prosthesis according to any one of claims 1 to 19, comprising a cell of synthetic resin material. 21. The vertebral disc prosthesis according to any one of claims 1 to 20, wherein the two coalescing plates (1, 2) are formed in the form of kidneys, ellipses or coils. 23. The vertebral disc prosthesis according to any one of the preceding claims, wherein the compressibility at the periphery is at least 0.7 mm, preferably at least 1.0 mm. 23. A vertebral disc prosthesis according to any of the preceding claims, wherein the compressibility at the periphery is at most 1.2 mm, preferably 3.5 mm. 24. The intervertebral disc prosthesis according to any one of the preceding claims, characterized in that the resilient means (3) is connected to the coalescing plates (1, 2) in a shape-fit or interference fit. The intervertebral disc prosthesis according to claim 1, wherein the two coalescing plates (1, 2) have an angle of 10 ° to 14 ° with respect to each other. 26. The vertebral disc prosthesis according to any one of the preceding claims, wherein the resilient means (3) can be assembled in one unit and on which two of the two plates are slidable or snappable.