DE4213771C1 - Spinal disc endoprosthesis - has elastic core with rim beading between shaped cover plates with a screw bonding for implantation without adhesive - Google Patents

Abstract

The endoprosthesis for a spinal disc (1) has two rigid cover plates (2,3) with an open mesh structure. The core (5) between them is of an elastic material. A ring beading (6) round the outer edge of the core (5) lies in matching troughs (11,12) round the cover plates (2,3). The cover plates (2,3) and the core (5) are held together by a screw bonding. USE/ADVANTAGE - The endoprosthesis is for the replacement of a disc in the spinal column as an implant. The structure is assembled as a compact implant, without adhesives, with a performance closely matching a natural spinal disc.

Description

The invention relates to a spinal disc endoprosthesis.

Basically, an artificial intervertebral disc should be behave like a natural intervertebral disc. She must keep the vertebrae at a distance from each other and any pressure on nerves or that Prevent spinal cord and tilt within the Buffer the spine by up to 5 °.

From EP-03 92 076 A1 is one Intervertebral disc prosthesis known from two rigid cover plates, between which there is a core is glued from an elastomer.

Basically, such Spinal disc endoprosthesis only works unfold if after the primary fixation of the Endoprosthesis by properly pinching it between two vertebrae to one Secondary fixation comes, so the implant one intimate bond with the neighboring vertebral bodies comes in. The above are probably for this purpose Cover plates on their after implantation Vertebral bodies facing outsides with a porous layer provided in the bone material should grow in. The elastic core at the known endoprosthesis closes on the end faces of the implant flush with the cover plates.  

The known implant has several disadvantages on. At this point, the following: The gluing of the cover plates with the elastic core is not without problems in With regard to the required durability. So body fluids can cause the Adhesive connection at least in the area of the end faces of the implant. In addition, leftovers the solvent of the glue or even Adhesive components in the surrounding tissue too Lead intolerance. Furthermore, here is the flush termination of the elastic core with the Cover plates addressed. It comes to that inclinations of up to 5 ° mentioned, this occurs Material of the core in the dorsal area from the Contours of the implant in a row Compensatory movement to those then acting Compression forces and can then possibly a highly undesirable pressurization of the lead adjacent spinal canal.

An intervertebral disc prosthesis consisting of two so-called end plates and one in between arranged spacer is known has become from DE 35 29 761 A1. The spacer consists essentially of a convex Middle part with a flat ring-shaped guide edge and with a ring bead and can, for example Polyethylene or polyurethane. Like these Parts into an implantable unit are joined together, for example by a This publication cannot be glued, etc. remove.  

As far as the technological background is concerned mentioned the following known publications: DE 30 23 353 A1, DE 22 63 842 A1, EP 03 56 112 A1, EP 02 98 235 and EP 03 17 972.

Against this background, it is now the task of present invention, a Specify intervertebral disc prosthesis without Use an adhesive to make a compact implantable unit is summarized, but nevertheless the functions of a natural one Intervertebral disc can exercise in good approximation.

This task is solved by one out of two rigid cover plates with open-mesh outer structure and a core of one between them elastic material existing Intervertebral disc prostheses in which the core is in a peripheral around its outer edge Has annular bead, which in accordingly trained circumferential troughs in the cover plates lies, and in which the cover plates and the core  by means of a screw connection are tense.

The parts of the endoprosthesis are replaced by a Screw connection to a compact unit put together. The external shape of the implant is in a known manner approximately kidney-shaped or rounded triangular design. About in the center this form is the screw connection between the Parts provided for what in the cover plates a hole is provided through which the screw which can be performed through the core one provided at the appropriate place Perforation engages. The screw connection is like this tight that a certain compression pressure is exercised on the core. Without further action there is - as is easy to see - the danger that despite the bias the core around the axis of the Screw connection could be twisted. To do this avoid, the design is the circumferential Ring bead in the outer edge area of the core intended. This is in the mentioned circumferential troughs in the cover plates. These Measure therefore offers a guarantee Self-centering of the elastic core. This is preferably made of silicone. The The modulus of elasticity of silicone is namely comparable to that of natural cartilage one natural intervertebral disc.

The core is preferably dimensioned such that it not completely flush with the face of the implant with the cover plates, so that under Loading a emergence of the core material from the Contours of the implant is impossible. But yourself if there is a flush conclusion, according to a advantageous development of the implant  provided that the nucleus is seen in its dorsal direction End face a groove-shaped material cut-out having. The cross section then offers the core its dorsal face the image of a lip-shaped training, the compensatory movements of the material under load without Core material leaves the contours of the implant, see above that the feared pressurization of the Spinal canal cannot occur. To the dynamic properties of the implant that one is closer to the natural intervertebral disc the screw connection according to an advantageous Embodiment specially trained. So is provided that the screw connection is made is by a threaded screw and a threaded sleeve each with a hemispherical head, the Heads in pan-like receptacles Grip inserts in the cover plates. Angle of inclination up to 5 ° under load are easy possible. So that it is due to micro movements of the Screw or nut head in the respective pan-like intake not to be questioned Material removals can occur, which exist Inserts mentioned preferably from low abrasion and low-friction material, such as polyethylene.

According to a further aspect of the invention, in advantageous further training provided that the Outside of each cover plate to the horizontal plane of the Kerns to its dorsal end face in one Angles in the range between 2 ° and 4 ° are inclined. This makes the implant easy wedge-shaped shape, so that it is in the Implantation easier in the ventral direction between two vertebral bodies can be used.

The invention is based on an embodiment explained in more detail with reference to the drawings. Here shows:  

Fig. 1 is a plan view of the endoprosthesis Banscheiben,

FIG. 2 shows a sectional view of the implant from FIG. 1.

In Fig. 1 is a plan view displayed on the intervertebral disc prosthesis according to the invention 1. As can be seen from this, the implant has an approximately kidney-shaped shape. From Fig. 1, a rigid cover plate 2 is seen to comprise an open-mesh outer structure 4. This serves for the secondary fixation of the implant in that bone material of the vertebral body lying against it after the implantation can grow through the outer structure. A threaded sleeve extends through the middle of the cover plate. Only the head 8 of this threaded sleeve can be seen in FIG. 1. Two stop bolts 14 are provided in order to achieve a defined position of the implant in the spine.

From the sectional view according to FIG. 2 it is clear how the two cover plates 2 and 3 enclose the elastic core 5 . The core 5 has a circumferential annular bead 6 which lies in appropriately shaped circumferential troughs 11 and 12 in the cover plate 2 and 3, respectively. FIG. 2 shows the particularly preferred screw connection which is produced by the threaded screw 20 and the threaded sleeve 21 . The threaded screw 20 and the threaded sleeve 21 each have a hemispherical head 7 and 8, respectively. In the cover plates 2 and 3 , an insert 9 or 10 is placed, in each of which a pan-like receptacle 15 or 16 is provided. The pan-like receptacles 15 and 16 are dimensioned such that the hemispherical heads 7 and 8 can perform a pivoting movement in them in all directions. In the exemplary embodiment shown, the threaded sleeve 21 engages through the bore 23 in the core 5 .

The inserts 9 and 10 advantageously consist of a low-abrasion and low-friction material, such as polyethylene.

The core 5 is dimensioned in the case shown that it does not protrude beyond the end edges of the cover plates 2 and 3 . Also an additional security against the above-mentioned pressurization of the spinal canal, the core 5 , seen dorsally, has a groove-shaped material recess 13 in its end face, so that an approximately lip-like shape is presented on this side.

About the position of the stop pin 14 on each top plate 2 and 3 it can be seen also from FIG. 2. These attach themselves to the vertebral body after implantation and give the implant a defined position.

The illustrated and particularly preferred embodiment of the implant allows the cover plates 2 and 3 to move to one another in all directions.

According to a further aspect, the outer sides of the cover plates 2 and 3 are inclined towards the horizontal plane H of the core 5 towards its dorsal end face 22 , namely at an angle α which is in the range from 2 ° to 4 °.

The cover plates 2 and 3 are preferably made of body-compatible metal, as is known from endoprosthetics.

Claims (6)

1. Intervertebral disc prosthesis ( 1 ), consisting of two rigid cover plates ( 2 , 3 ) with an open-mesh outer structure ( 4 , 4 ß) and a core ( 5 ) stored between them made of an elastic material, in which the core ( 5 ) in its outer Edge region has a circumferential annular bead ( 6 ) which lies in appropriately designed circumferential troughs ( 11 , 12 ) in the cover plates ( 2 , 3 ), and in which the cover plates ( 2 , 3 ) and the core ( 5 ) are connected to one another by means of a screw connection are tense. 2. Intervertebral disc prosthesis according to claim 1, wherein the core ( 5 ) consists of silicone. 3. Intervertebral disc endoprosthesis according to claim 1 or 2, in which the screw connection is produced by a threaded screw ( 20 ) and a threaded sleeve ( 21 ), each with a hemispherical head ( 7 , 8 ), the heads ( 7 , 8 ) being in pan-like receptacles ( 15 , 16 ) having inserts ( 9 , 10 ) in the cover plates ( 2 , 3 ). 4. intervertebral disc prosthesis according to claim 3, wherein the inserts ( 9 , 10 ) consists of low-abrasion and low-friction material. 5. Intervertebral disc prosthesis according to one of claims 1 to 4, in which the core ( 5 ), seen dorsally, has a groove-shaped material recess ( 13 ) in its end face. 6. Intervertebral disc prosthesis according to one of claims 1 to 4, in which the outside of each cover plate ( 2 , 3 ) to the horizontal plane (H) of the core ( 5 ) to the dorsal end face ( 22 ) are inclined at an angle α, wherein α im Range is 2 ° <α <4 °.