DE4315757C1 - Vertebral implant - Google Patents

Description

The invention relates to a vertebral implant according to the Preamble of claim 1. Such a vertebral body plantat is generally known. It will refer to this a special print "Spinal Surgery II - Operative Be act of chronic low back pain, symposium Augsburg 1991, edited by Klaus A. Matzen, Georg-Thieme-Verlag Stutt gart, New York 1992 ". This reprint represents the Development of artificial intervertebral discs and the current one Summary of the development. Accordingly, the current state of the art a three-part modular Intervertebral disc prosthesis consisting of two concavely hollowed me metallic end plates made of a chrome-cobalt alloy and an intermediate central lenticular poly ethylene (chirules) sliding core. With the material pairing Me tall / polyethylene is said to have low sliding friction be guaranteed. Anchoring the Ab final or upper and lower cover plates are made via  ring-shaped or row-shaped spines on the bony Vertebral end plates. The constructive design of the biconvex sliding core with a circular ring wall both segmental movements in the extension-flexion Plane, sideways tilt and rotation are enabled. At the same time, however, Be beyond 10 to 15 ° movement rashes and a dislocation of the polyethylene lens in extreme movement positions can be prevented. The featured intervertebral disc prosthesis is among others in the EP 0 176 728 B1. The problem with this be knew the construction and limited by cold flow and Embrittlement with time decreasing elasticity of the polyethylene len sliding core. It has also been shown in practice that the polyethylene sliding core to the Un after a relatively short time usability is destroyed, especially on the edge. This in turn leads to a follow-up operation that is avoided if possible that should be.

The present invention is based on the object constructively ver compared to the prior art to create a simple vertebral implant that visibly the function of the natural intervertebral disc if possible comes close and still has the advantage, ver to be wear-free and therefore correspondingly durable. Ver wear-related follow-up operations should therefore be carried out with the inventor vertebral implant according to the invention can be avoided.

This task is characterized by the characteristics of the contractor Proverb 1 solved.

The vertebral body implant according to the invention is accordingly did essentially reduced to one essential Component, namely on a specially shaped spring element. in the Extreme case, namely according to claim 2, we exist Fibrous implant practically exclusively from the invent appropriately trained spring element. This is wear free. It consists of only one, i.e. H. uniform, biocompatible material. The construction according to the invention  is characterized by the extreme reduction of building components len, their extremely simple construction and thus manufacture as well as its extremely simple handling with the Implan tion.

The operative handling of the implant according to the invention can also be made considerably easier by the Measures according to one of claims 8 to 10.

Experiments have shown that the vertebral body according to the invention perimplant surprisingly has a recurrence curve points that largely ent of that natural intervertebral disc speaks. This applies to both the extension-flexion level as well as for the sideways tilt. A rotation allows that Construction according to the invention, however, does not. This little In practice, the disadvantage is not a disadvantage because the rotation deflections even when the intervertebral disc is intact are only minor, so that the invention conditional restriction is not recognized as an actual disadvantage bar makes.

Further advantageous structural details of the invention ß vertebral implant are in the dependent claims wrote. Here is still the constructive solution according to An saying 6 highlighted. In this is the invention Spring element encapsulated on all sides. So the implant provides is a closed system.

The dimensioning of the implant according to the invention is like this chosen that at a disc thickness of about 12 mm segmental mobility of about 5 ° is achieved. At Thick intervertebral discs can still segmental mobility increase.

Preferred embodiments of the invention are described below vertebral body implant according to the attached schematic drawing explained in more detail. Show it:  

Figure 1 shows a first embodiment of a vertebral implant designed according to the invention in a perspective view.

FIG. 2 shows the implant according to FIG. 1 in a front view in the direction of arrow II in FIG. 1;

FIG. 3 shows the implant according to Figure 1 in side view in the direction of arrow III in Fig. 1.

FIG. 4 shows a modified vertebral body implant according to the view according to FIG. 3;

FIG. 5 shows the implant according to Figures 1-3 in quantitative together drücktem state prior to insertion between two adjacent vertebral bodies and in side view.

Fig. 6, the implant according to Figures 1-3 in view together quantitative drücktem state before insertion between two adjacent vertebral bodies in perspective on.

FIG. 7 shows a third embodiment of the present invention formed in the vertebral body implant schemati's longitudinal section, wherein the elastic intermediate element is indicated with a dashed line; and

Fig. 8 is a capsule for the implant of FIG. 7 in a greatly enlarged scale showing the relati ven mobility of the upper and lower shell of the implant capsule.

The vertebral implant shown in Figs. 1-3 be available from a between adjacent and not shown in detail here vertebral bodies insertable spacer body 10 comprising an upper cover plate 11 and a lower cover plate 12 and a valve disposed between the two cover plates fe derelastisches intermediate element 13. Spike-like vertebral body anchoring elements 14 , 15 and 16 are arranged on the outer or on the sides of the cover plates 11 and 12 facing the vertebral bodies. After the insertion of the vertebral body implant, these penetrate between two adjacent vertebral bodies into the vertebral body bones. As a result, the implant is firmly anchored between two adjacent vertebral bodies. The resilient intermediate element 13 is formed by an S-shaped plate 17 made of biocompatible material, in particular titanium, a titanium-coated cobalt-chromium-molybdenum, cobalt-chromium or stainless spring steel alloy or the like. The wall thickness of the spring plate is about 0.2-0.6, especially about 0.35 mm. The upper and lower cover plates 11 and 12 and the spring element 13 arranged between them are formed approximately oval in plan view. A kidney-shaped contour is also conceivable. Furthermore, in the embodiment according to FIGS. 1-3, as in the embodiment according to FIGS. 4-6 described in more detail below, the upper and lower cover plates 11 and 12 are an integral part of the spring-elastic intermediate element 13 or the S-shaped curve Plate 17 . That is, the upper and lower cover plates 11 and 12 are formed by the two free legs of the S-shaped plate 17 .

Alternatively, according to FIG. 4, the resilient intermediate element 13 can be formed by a W-shaped plate 17 . The simplest embodiment is a U-shaped spring plate.

As can be seen from FIGS. 2 and 3, the two cover plates 11 and 12 are each convex on the outside, both in their longitudinal direction and transversely thereto. This results in better embedding or anchoring on the respectively assigned vertebral bone.

According to FIGS. 3 and 4 close both Deckplat th 11, 12 in the relaxed state of the resilient Zvi rule elements 13 in a plane perpendicular to its longitudinal extension forms an angle α of about 3 ° to 25 °, in particular about 8 °. The implant is then inserted between two adjacent vertebral bodies so that the higher side is at the front. Then the desired elasticity and damping properties are guaranteed both in the extension-flexion plane and in the event of a sideways inclination.

According to FIGS. 7 and 8, the resilient intermediate member in an alternative embodiment, z. As shown in FIGS . 1-3 within a capsule 20 formed by an upper shell 18 and a lower shell 19 , caps may be enclosed or enclosed, the upper and lower cover plates then being part of the upper and lower shells 18 and 19 , respectively. Accordingly, the above-mentioned spikes 14 , 15 and 16 are also arranged on the outer sides of the upper and lower shell.

The upper shell 18 and lower shell 19 consist of biocompatible material, in particular titanium sheet. They are so miteinan connected, in particular according to FIGS . 7 and 8 hooked together at the edges that they can follow the movement of the resilient intermediate element 13 without play. In Fig. 8 the relative mobility between the upper and lower shell is shown schematically. Accordingly, the segmental mobility should be approximately 5 °. This corresponds to an implant height of approximately 12 mm.

According to Fig. 7, upper and lower shells 18, 19 are each curved convexly. This curvature gives the half-shells 18 , 19 additional inherent stability, with the result that they can be made from thinner sheet metal without the risk of breakage. Above all, it is possible with this embodiment, to make the central region of the upper and lower shells extremely thin-walled, while in the area of the peripheral edge of the upper and lower shells the wall thickness of the same is chosen to be larger. In the central area of the upper and lower shell, when using a titanium sheet, the maximum wall thickness is approximately 0.05 to 0.25 mm, in particular approximately 0.10 mm. The wall thickness then preferably increases continuously by about 25-50% towards the peripheral edge.

In the embodiment according to FIG. 8, the wall thickness of the upper and lower shells 18 and 19 is approximately 0.10-0.30 mm, in particular approximately 0.15 mm.

The embodiment according to FIGS. 7 to 8 represent a closed system. Within the capsule 20 , a spring element other than that according to FIGS. 1-3 or according to FIG. 4 can also be arranged. In principle, the arrangement of a coil spring package is also conceivable. Above all, cone pressure springs have proven to be advantageous with regard to their spring characteristic.

It should also be noted that in all embodiments, the length of the spikes 14 and 15 lying at the front in the inserted state is greater than the length of the rear spike 16 . This is related to the space between two adjacent vertebrae.

To avoid a complicated tool for implantation, it is advantageous that the described vertebral implant tate before insertion between two adjacent vertebral cores by a removable compression band 21 after insertion, a compression wire, a compression clip or the like. In the direction of action of the resilient intermediate element is compressed. In this regard, reference is made to FIGS. 5 and 6. By means of the compression band 21 , the implant can be compressed before insertion between two adjacent vertebral bodies by about ¼ of its maximum height plus the height of the vertebral body anchoring elements (spikes 14 , 15 , 16 ). This means that the implant can be inserted between two adjacent vertebral bodies without the need for spreading tools or pliers. The compression band is then opened and removed. The implant expands in the axial direction of the spine under the pretension of the spring-elastic intermediate element. The spikes 14 , 15 and 16 penetrate into the bones of the associated vertebral bodies. Accordingly, the implant anchors itself.

Preferably, the compression band 21 as shown in FIG. 6 is extending within a around the implant 10 around, in particular, arranged within an externally formed on upper and un more excellent cover plate 11, 12 groove 22. The depth and width of this groove 22 corresponds approximately to the thickness and width of the compression band 21 . Instead of a compression band, a compression wire or the like can also be used. In the present case, the two ends of the compression band 21 are tacked together at the front of the implant 10 (soldered connection or the like). This connection is released after inserting the implant, e.g. B. opened by means of a side cutter. When using a compression wire, this can be twisted on the front of the implant 10 . After inserting the implant, the twisting is released and the wire around the implant is pulled out to the front.

Basically, it is also possible to use the top and bottom provide recesses or openings on the side of the implant, in which the tines of a pair of pliers can be inserted to the Im implant for insertion between two adjacent vertebrae press together. The above solution with a comm Press band or the like is however more elegant in that the relatively high compression pressure already at the manufacturer tion of the implant can be applied. This compress Sionsdruck then only needs after inserting the implant to be solved by opening the compression band or the like. Of course, the compression band made from biocompatible material.

Instead of convexly arching the upper and lower cover plates 11 and 12 in the embodiment shown in FIGS . 1-3, it is also conceivable to mount convexly curved and spiked cover plates on the legs of the spring element 13 , z. B. screw. This embodiment has the advantage that the arching of the cover plates 11 and 12 can be selected individually for the patient.

In the illustrated embodiments, the side flexi the implant is slightly less than in the lower plane right to the length of the implant. Accordingly the implant is also inserted so that the plane transverse to the longitudinal extension parallel to the extension-flexion Level of the patient extends. At this level, that's Im Accordingly, plantat is highly flexible. Towards the side, d. H. the implant is harder for sideways inclination. In this respect, the implant approaches the effect of the natural one Chen intervertebral disc. For the right or left sideways movement is namely a maximum of about half the mobility estimated at the front and back. That demand will be the implants described.

For the rotation of the individual vertebrae against each other the segmental movements are between 2 and 4 °. These are therefore for the construction of an implant generally neglect. Accordingly, at the described embodiments no rotation of the Im plantate provided. This allows the construction to be done entirely simplify considerably.

Claims (12)

1. vertebral body implant, consisting of a spacer body ( 10 ) which can be used between adjacent vertebral bodies and which comprises an upper ( 11 ) and a lower ( 12 ) cover plate and an intermediate spring-elastic intermediate element ( 13 ) arranged between these two cover plates, with the outer or on the sides of the cover plates facing the vertebrae vertebral body anchoring elements ( 14 , 15 , 16 ) are provided, characterized in that the resilient intermediate element ( 13 ) by an approximately U-, S- or W-shaped plate ( 17 ) made of biocompatible material, in particular titanium, a titanium-coated cobalt-chrome-molybdenum, cobalt-chrome or stainless spring steel alloy. 2. Implant according to claim 1, characterized in that the upper and lower cover plate ( 11 , 12 ) are integral components of the U-, S- or W-shaped spring plate ( 17 ) and the upper and lower cover plate by the two free legs the U, S or W-shaped spring plate ( 17 ) forms ge. 3. Implant according to claim 1 or 2, characterized in that the upper and lower ( 11, 12 ) cover plate are each oval or kidney-shaped in plan view. 4. Implant according to one of claims 1-3, characterized in that the two cover plates ( 11 , 12 ) are each convex on the outside or curved. 5. Implant according to one of claims 1-4, characterized in that the two cover plates ( 11 , 12 ) in the relaxed state of the spring-elastic inter mediate element ( 13 ) in a plane perpendicular to their longitudinal extent (in the extension-flexion plane) an angle Include (α) from about 3 to 25 °, especially about 8 °. 6. Implant according to one of claims 1 or 3-5, characterized in that the resilient inter mediate element is enclosed within a capsule ( 20 ) formed by upper ( 18 ) and lower ( 19 ) shell, the upper and lower Cover plate are part of the upper ( 18 ) and lower ( 19 ) shell. 7. Implant according to claim 6, characterized in that the upper ( 18 ) and lower ( 19 ) shell made of biocompatible material, in particular titanium sheet and are connected to one another, in particular are hooked on the edges, that they move the Be without movement can follow resilient intermediate element ( 13 ). 8. Implant according to one of claims 1-7, characterized in that it is inserted between two adjacent vertebral bodies by a removable compression band after insertion ( 21 ), a compression wire, a compression clamp or a similar compression device in the effective direction of the resilient Intermediate element ( 13 ) is compressed. 9. Implant according to claim 8, characterized in that it is compressible before insertion between two adjacent vertebral bodies by about ¼ of the maximum height plus height of the vertebral body anchoring elements ( 14 , 15 , 16 ). 10. Implant according to claim 8 or 9, characterized in that the compression band ( 21 ) or the compression device within an extending around the implant ( 10 ) around, in particular within an outside at least on upper and lower cover plate ( 11 , 12 ) formed Groove ( 22 ) is located, the depth and width of which corresponds approximately to the thickness and width of the compression band ( 21 ) or the compression device. 11. Implant according to claim 6, characterized in that the wall thickness of the upper ( 18 ) and lower ( 19 ) shell is approximately 0.10-0.30 mm, in particular approximately 0.15 mm. 12. Implant according to claim 6 or 11, characterized in that in the region of the peripheral edge of the upper ( 18 ) and lower ( 19 ) shell, the wall thickness of the same is greater than in the central region, the wall thickness there being a maximum of about 0.05. 0.25 mm, in particular about 0.10 mm.