DE2263842A1 - DISC PROTHESIS - Google Patents

Description

Intervertebral disc prosthesis The invention relates to an intervertebral disc prosthesis.

It is well known that there are a large number of physical injuries and impairments of well-being due to the fact that an intervertebral disc, one of the elastic Pillow between two vertebral bodies of the spine, no longer fulfilling its task Fulfills.

According to the invention, this can be eliminated in many cases or at least mitigate the consequences that the intervertebral disc is replaced by a prosthesis will. The intervertebral disc prosthesis according to the invention is characterized in that it is designed as a spacer which can be inserted between two vertebral bodies by means of arched Sliding surfaces an inclination and / or the vertebral body allowed against each other. It is an advantageous embodiment because of its simplicity characterized in that the prosthesis as between the base plate of an upper and the cover plate of a lower vertebral body insertable, at least above and below approximately lens-shaped arched end faces having a disc is formed, whose end faces on the circumference have such a distance from one another that the two Vertebral bodies do not touch each other when the spine is curved.

In the simplest case, the intervertebral disc prosthesis consists of a rigid one Body, for example made of one of the usual and proven metal alloys for endoprostheses or from a suitable plastic, which has also been tried and tested for this purpose.

Corresponding materials are known from prosthetic technology. Owns the prosthesis has precise, rotationally symmetrical lens surfaces, e.g. spherical cap-shaped End faces> so before the insertion of the prosthesis between two vertebral bodies the cover plate of the lower vertebral body and the base plate of the upper vertebral body in the area between the actual vertebral body and the natural intervertebral disc located cartilage layer are processed so far that the processing resulting bearing surface of the vertebral body is at least approximately the same as the corresponding one Lens surface of the prosthesis. Superior to others in various relationships, later to illustrative embodiments of the invention can also be the corresponding Surface of the prosthesis designed according to the natural surface of the vertebral body so that milling or other processing of the bearing surface between Vertebral body and prosthesis is not required.

The prosthesis according to the invention has a number of functions to meet at the same time. On the one hand, it holds the two adjacent vertebral bodies in place Axial direction at a distance, so that even when these two vertebral bodies are angled while the spine is curved, the two neighboring ones collide against each other Vertebral body is certainly avoided. This is essential because such a push leads to highly undesirable changes in the two neighboring ones Vertebral body leads. In order to avoid such a bump with certainty, must the intervertebral disc prosthesis all axial forces occurring between the vertebral bodies without excessive compression. Furthermore, the intervertebral disc prosthesis have sufficient elastic strength to allow them to occur when such Axial forces not too far in the radial direction from the gap between two vertebral bodies steps out. To enable the neighboring vertebral bodies to bend towards each other, In the simplest case, the prosthesis is exactly spherical cap-shaped on both end faces shaped and preferably also polished smooth, so that the vertebral bodies themselves with their cartilage frontal surfaces, which in this case should be milled off as little as possible, on the intervertebral disc prosthesis can slide. Due to the lens-shaped or spherical cap-shaped design of the both end faces of the intervertebral disc prosthesis will result in a displacement of the two adjacent, vertebral bodies supported on each other by the prosthesis in a lateral direction as well prevents the vertebral bodies under the influence of the muscles in the axial direction are tense against each other. Even if the prosthesis can be bent well vertebrae kept at a distance from one another is desirable, but so are the two other demands of keeping in flight and preventing collision when bending the more important ones. The height of the disc prosthesis according to the invention depends largely on the size of the vertebral bodies to be separated by the prosthesis away. At the edge, the thickness of the prosthesis should be advantageous between that in the middle 10 and 14 mm, about 5 to 10, preferably about 6 to 8 mm.

The diameter of the prosthesis lies with the smallest thickness of the prosthesis advantageously of the order of 30 mm, while it is stated at the largest Thickness is advantageously in the order of about 40 mm.

What is essential in all embodiments of the prosthesis is the Invention that this must not be arbitrarily compressible, but at least in the middle only slight fluctuations in the distance between the two vertebral bodies may allow, while also on the edge a possibly existing compressibility A certain amount should not be exceeded and, moreover, should not lead to large changes in diameter the prosthesis should lead. If the prosthesis is made in one piece, it can as mentioned above, be a rigid body. However, it preferably has at least an elastic intermediate layer that is in a plane normal to the axis of the prosthesis (which coincides with the axis of the vertebral bodies) extends. The elastic intermediate layer can, for example, consist of a suitably age-resistant and body-friendly Consist of silicone rubber. If you make sure that, for example, in the middle of the Intermediate layer a little or no elastic spacer or even only a harder area of the elastic intermediate layer is provided, so the Edge areas are correspondingly more elastic, which means that they can be bent of the vertebral bodies separated by the prosthesis against each other without sliding of the convex prosthesis end faces in the correspondingly concave vertebral body end faces is. This is a major advantage over the rigid training.

The elastic intermediate layer can, for example, from a Cylindrical disk be formed, which is vulcanized between two Rugelkalottenkörper. she can but also themselves have lens-shaped end faces which are provided with rigid covers are.

The prosthesis can also consist entirely of a rubber-elastic material. In this case, the Shore hardness should not be less than, for example, for the treads of automotive rubber tires is chosen. Do you want a softer one You can choose rubber-elastic material for a solid or full denture Do this if you have a correspondingly rigid insert, e.g. in the form of a of a thin, vulcanized metal plate, which has a strong radial Expansion of the prosthesis and thus also a strong axial compression of the prosthesis prevented.

The prosthesis according to the invention preferably consists of at least two superposed mutually displaceable parts, each of which on a of the two vertebral bodies connected by the prosthesis. In the simplest case such a construction can be realized in the manner set out above, in which an elastic intermediate layer at the top and bottom is harder, at least on the outside bears domed panels. When talking about movable parts here, they should these parts cannot be displaced against each other at will be. she rather, on the one hand, against each other by a certain amount (that by the above mentioned requirement that the two vertebral bodies when angled against each other may not touch, is limited) be angled or inclined. You should, however if possible not or only slightly against each other in a normal plane to the longitudinal axis the spine can be moved. Some axial compressibility of the both parts is admitted. However, this should remain quite low. The less the two parts can be axially pressed together, the more they can against each other be inclined without the adjacent vertebral bodies touching each other. The great The advantage of the displaceable arrangement just explained is that the two parts that can be moved against each other are necessary when bending the spine Perform relative movement between themselves and no longer relative to the vertebral bodies.

For the question of whether the lens-shaped curved end faces are rotationally symmetrical or should develop differently from this, it is important whether the prosthesis is in is rotatable by itself to a certain extent or not. Is the prosthesis in itself itself not or not sufficiently rotatable to accommodate the natural rotational movements of the To allow the spine, the end faces should be rotationally symmetrical, there then the relative movements when turning between the end faces and the both vertebral bodies. On the other hand, is the prosthesis sufficient in itself? rotatable, so you can see the end faces of the vertebral bodies from the rotationally symmetrical Shape deviates more precisely from the natural shape of the cover plate or the base plate of the corresponding vertebral body or another fixed in the vertebral body give anchored form.

A prosthesis made up of two mutually displaceable ones arranged one above the other Sharing, as just explained, can be created, for example, by that they are composed of a biconvex lens body and a concave-convex lens body, in which the former is slidably mounted. In this case has at least advantageous one of the two lens bodies at the edge a certain thickness to also in the angled State of keeping the two vertebral bodies at a distance. The two lens bodies should here from a favorable material pairing, for example a plastic and consist of a metal, which have good emergency running properties against each other. Corresponding material pairings are, for example, from hip joint prosthesis technology known where the pan is often made of a suitable plastic, while the joint ball is made of metal. The form of training just described has the major advantage that it not only prevents the bending movement of the neighboring Vertebral bodies against each other, but about it also is rotatable in itself. That is, a relative movement between the prosthesis and Vertebral bodies is not required. The construction just described can can also be made elastic, e.g. by inserting a uses elastic intermediate layer. Not only in this one, but also in others Embodiments can also be a liquid-filled one instead of an elastic intermediate layer flexible hollow body should be provided, provided that the prosthesis parts move is prevented against each other on both sides of the hollow body.

A somewhat more complex construction, but the biological one A prosthesis that meets requirements particularly far can be achieved by using an embodiment of the #prothesis with two stacked against each other displaceable parts the latter as connected to one another by a pivot bearing, preferably designed as a half-lens body forms support plates. As a half lens body here are two relatively flat disks, each with an outer lens surface. The outer lens surface can be designed to be rotationally symmetrical as well as being better suited to the exact shape of the vertebral end faces. The support plates can on their vertebral bodies facing surfaces z.

B. be flat and carry anchoring projections in the form of thorns. In the simplest case, the pivot bearing can be, for example, a short silicone rubber body educated be which the two support plates at a sufficient distance holds and at its two end faces with the mutually facing surfaces of the Support plates is vulcanized together. However, a pivot bearing is preferred central body with two spherical cap surfaces on which the support plates are stored with corresponding sliding surfaces. The sliding surfaces are preferred spherical central recesses with at least approximately the same radius of curvature like the spherical cap surfaces. The two spherical cap surfaces complement each other preferably to a spherical surface. Here, too, the materials are beneficial chosen that favorable sliding properties between the central body and the support plates available. The latter can, for example, be made of metal and the central body consist of a corresponding plastic or vice versa.

When the prosthesis is made up of two by means of a pivot bearing interconnected support plates is the space between the central Pivoting and the two edges of the support plates advantageously with an elastic Displacement body filled. This displacement body can, for example, a This space completely fills the ring made of closed-cell silicone rubber be. However, a body made of silicone rubber or the like is preferably used here selected, which has, for example, approximately double-T profile, the web of the double-T profile lies in a normal plane to the axis of the prosthesis and which are mutually exclusive facing surfaces of the two Support plates on the free edges the two flanges of the double-T profile are supported. For the latter purpose you can the two free edges of the flanges have widenings that attach to the support plates issue. The filler body is preferably rubber-elastic. If desired, he can be vulcanized together with the two support plates. If you vulcanize it together, however, this reduces the rotatability of the prosthesis # in itself. If the rotatability of the prosthesis is nevertheless to be maintained, this can be done achieve by keeping the flanges and webs of the filler body relatively thin. In general, however, one will prefer a design that is not vulcanized together, in which only, for example, the inner flange of the double-T profile in a corresponding ring groove engages each of the corresponding support plate and this also holds the parts of the prosthesis together.

It is to be understood that the various features set forth above different embodiments, as far as this makes sense, also combined with one another can be. For example, a displacement ring body made of sponge rubber also be vulcanized together with two half-lens bodies if you have a smaller one Takes the rotatability of the two semi-lens bodies into account.

The subject matter of the invention is shown in the following on the basis of the drawing different embodiments explained in more detail.

Fig. 1 shows schematically a section in the plane of symmetry of the skeleton by two vertebrae located on top of each other, which by means of a prosthesis according to the Invention are supported on each other.

Fig. 2 shows the view from above of the front part of the lower 1 as well as the prosthesis according to the invention lying on the vertebral body.

Fig. 3 shows the prosthesis according to FIGS. 1 and 2 in approximately natural size of the page.

FIG. 4 shows the view from above of FIG. 3.

Fig. 5 shows an axial section through a second embodiment a likewise rotationally symmetrical prosthesis according to the invention.

FIG. 6 shows a further embodiment in the same representation as FIG.

7 shows, on a significantly enlarged scale, what is considered to be optimal Embodiment of the prosthesis according to the invention in axial section.

Fig. 8 shows a slightly modified approximately natural size Embodiment of the prosthesis according to FIG. 7 FIG. 9 shows the same representation as FIGS. 5 and 6 show a modified embodiment of the prosthesis according to FIG. 6.

In Fig. 1 a prosthesis 1 according to the invention is in its position between the base plate of an upper vertebral body 2 and the cover plate of a lower vertebral body 3 shown.

The upper and lower cartilage layers of vertebral bodies 2 and 3 are indicated by thickened boundary lines 4.

It can first be seen from the drawing that all the exemplary embodiments shown the prosthesis according to the invention in the view in the longitudinal direction of the spine seen in contrast to a natural intervertebral disc at least approximately and preferably are circular. Basically, in different versions, such as 6 and 7, a non-round design is also possible. With regard to However, it is due to the considerably greater technical effort that this entails which is preferred in the view, for example, according to FIG. 2, the circular design.

The prosthesis according to the invention shown in FIGS. 1 to 4 represents the represents the simplest embodiment of a prosthesis.

It can be rigid, for example made of metal or plastic, or else made of a rubber-elastic material, such as e.g.

a silicone rubber of sufficient Shore hardness. the Conditions which determine the hardness have already been set out above. The prosthesis consists here of a solid body, which has a rotationally symmetrical upper lens-shaped End face 5 and a lower, rotationally symmetrical end face which is also designed 6 owns. The radius of curvature of the end faces 5 and 6 is on the one hand small enough to a lateral displacement of the vertebral bodies 2 and 3 in a normal plane to Backbone to prevent hse 7. On the other hand, it is so big that there are no major ones Explosive forces are exerted on the vertebral bodies 2 and 3.

The curvature of the end faces 5 and 6 need not be exactly spherical be. Other rotation curves, such as parabolas, are also possible here. What is decisive is the best possible approximation of the surfaces 5 and 6 defining Rotation curves to the natural shape of the base plate and the top plate of the vertebrae.

The prosthesis 1, like the prosthesis 5, must be rotationally symmetrical be designed, since in both cases sliding in the event of torsion of the spine takes place between the prosthesis and the vertebral body.

The prosthesis 1 has rounded edges 8. The peripheral surface 9 is convex, so that all surfaces merge continuously into one another. the Height of the circumferential surface 9 is chosen so that the largest possible to be expected Angulation of the two vertebrae held at a distance by the prosthesis against each other the opposite edges of the vertebral bodies do not collide can.

The prosthesis can be made of elastic material. The elasticity is allowed however, it should not be too large so that the prosthesis is not compressed in the axial direction can be. Such a prosthesis is therefore made from rigid in many cases Prefer material.

In Fig. 5 a further prosthesis 12 according to the invention is shown. This prosthesis has an upper, rotationally symmetrical plate 13 and the other way around curved lower plate 14. Both plates can, for example, from a corresponding suitable metal alloy. They preferably have constant wall thickness, as indicated in the drawing. They are made of an elastic plastic insert 15 kept at a distance, which is vulcanized together with the two plates 13 and 14 is. To keep the plastic insert 15 as elastic as possible in the edge areas to be able to slide the plates 13 and 14 on the vertebral bodies held at a distance when tilting the same to reduce each other to a minimum, the axial compressibility of this prosthesis must be low in the middle. to For this purpose, the central core 16 of the rubber-elastic insert 15 with a equipped with a much harder Shore hardness.

The outer shape of the prosthesis 12 advantageously corresponds to that of the prosthesis 1.

The intervertebral disc prosthesis 18 shown in FIG. 6 is constructed in two parts. It consists of a relatively rigid, rotationally symmetrical plastic body 19, which cooperates with a likewise rotationally symmetrical! Ttallschale 20. The lower surface of the plastic body 19 and the surface of the metal shell 20 have the same radius of curvature, which is constant everywhere, so that the two Parts can be rotated and inclined against each other and in doing so perfectly slide. This has the advantage that the upper surface 21 of the body 19 is also asymmetrical can be designed to better match the baseplate of the upper vertebral body to enable. The same applies mutatis mutandis to the lower surface 22 of the lower one Part 20 of the prosthesis. The circumferential edge 23 of the prosthesis hits if it is excessive Moving the two prosthesis parts 19 and 20 against each other on the Edge of the other prosthesis part 20, which again ensures here, too, that the vertebral body edges when bending the vertebrae against each other do not touch.

The prosthesis shown in Fig. 7 consists essentially of two of the parts referred to above as half-lens bodies. Both half lens bodies 25 of the in Fig. 7 are the same prosthesis. The two end faces of this prosthesis are lenticular, namely rotationally symmetrical or, on the outside, more precisely to the corresponding one Adapted to the bearing surface of the vertebral body.

The two half-lens bodies 25 each carry a spherical one in the center LagerpRanne with which they rest on a central joint ball 26 so that they are pivotable relative to one another around the center of this ball. they are furthermore rotatable relative to one another. The formation of perfect storage areas for the ball 26 inwardly protruding parts of the half-lens body 25 have a such a distance from each other that they pivot towards each other # the half-lens body 25 do not oppose this. These protruding parts are annular on both sides Turns 27 into which a rubber-elastic intermediate body 28 with lips 29 engages so that it counteracts the two semi-lens bodies 25 with a slight bias the ball 26 d # kt, which is advantageous in the case of the semi-lens body made of metal Plastic is made or vice versa. The rubber-elastic Zwisvhenring 28 has a Double T profile. The lips 29 belong to the radially inner flange of this double-T profile on, its bridge in the horizontal axis of symmetry in FIG Prosthesis lies. The radially outer flange of the double-T profile of the body 28 supports with its corresponding edges 30 on the inner surfaces of the half-lens body 25 from. As a result, the filling body 28 acts with increasing pivoting of the semi-lens body 25 against each other also with increasing force a further pivoting against each other opposite. To make it easier to rotate the two half-lens bodies 25 about the axis 31 to enable each other, the filling body 28 is not with the two half-lens bodies 25 vulcanized together.

However, the latter is also possible. In the latter case, however, you give the end faces of the prosthesis advantageously one for the reasons set out above rotationally symmetrical shape.

The prosthesis 35 shown in FIG. 8 differs from the prosthesis 26 essentially only in that a double lens body instead of the central ball 36 is provided, in which, although the position of the exact pivot point of the the two half-lens bodies 37 and 38 are indeterminate with respect to one another, but the bearing forces between the half lens bodies and the central double lens body 36 more favorable are.

Fig. 9 shows a further prosthesis shape 40 which is also a upper half lens body 41 and a lower half lens body 42 has. Advantageous there is one of the two semi-lens bodies made of a plastic, while the the other of the two consists of a metal which, together with the plastic, has good sliding properties Has. The upper half-lens body 41, for example, has a central spherical cap-shaped shape Projection 43, whose center of curvature is preferably with the center of the rest rotationally symmetrical prosthesis. The lower half lens body 42 has also a central projection 44, which has a central recess, whose radius of curvature is equal to that of the ball projection 43, so that in this way the two half-lens bodies 41 and 42 against each other around the center of the prosthesis are pivotably and rotatably mounted in one another. Swinging too much towards each other the two half-lens bodies can, for example, by dimensioning them accordingly the outer edges of the same can be prevented. However, there is also the possibility here a filler, such as that made of closed-cell silicone sponge rubber existing filler ring 45. Is the fill ring 45 not with the half lens bodies 41 and 42 vulcanized together, the latter can also not be rotationally symmetrical Surfaces have to better conform to the surfaces of the vertebral bodies to enable.

Not only the prostheses as such, but also their parts can also be modified depending on the circumstances. For example, the Filling ring or intermediate ring 28 also has a U-profile shape instead of the double-T profile shape obtain. For this purpose, it is sufficient to move the web of the double-T profile to the side to move so that he attaches the ends of the two flanges of the double-T profile to this Page connects. Another possibility is that you can use the web of the double-T profile omits at all. In this case, however, the outer flange must also be in a corresponding annular groove of the two semi-lens bodies 25 engage so that he himself can not move radially.

The intermediate body can also have holes, which in this case should be so large that they allow the body to enter and exit effortlessly Allow liquid.

This avoids an air or gas-filled space in the prosthesis. Such through holes can either only in the outer flange or both in the outer flange as well as in the inner flange of the intermediate body or filler body be provided. In many cases, the arrangement of these holes in the outer flange is alone suffice.

Claims (9)

Patent claims: k intervertebral disc prosthesis, characterized in that it is used as between two vertebral bodies insertable spacer is formed, which by means of arched Sliding surfaces allow an inclination and / or the vertebral bodies against each other. 2. Intervertebral disc prosthesis according to claim 1, characterized in that that they are at least approximately lens-shaped curved end faces at the top and bottom having disc is formed, the end faces of which on the circumference such Have a distance from each other that the two vertebral bodies each other in the curvature do not touch the spine. 3. Intervertebral disc prosthesis according to claim 1 or 2, characterized in that that it has at least one elastic intermediate layer, which is in a normal plane extends to the prosthesis axis. 4. Intervertebral disc prosthesis according to claim 1, 2 or 3, characterized in that that it consists of a rubber elastic material. 5. Intervertebral disc prosthesis according to one of claims 1 to 4, characterized characterized in that they consist of at least two on top of each other arranged there are mutually displaceable parts, each of which passes through one of the two the prosthesis is connected to the vertebral body. 6. Intervertebral disc prosthesis according to claim 5, characterized in that it has a biconvex lens body and a convex-concave lens body in which the former is slidably mounted. 7. Intervertebral disc prosthesis according to claim 5, characterized in that they are two connected to one another by a pivot bearing, preferably as a half-lens body has formed support plates. 8. Intervertebral disc prosthesis according to claim 7, characterized in that a central body with two spherical cap surfaces serves as a pivot bearing which the support plates with spherical central recesses of at least approximated with the same radius of curvature. 9. Intervertebral disc prosthesis according to claim 7 or 8, characterized in that that the support plates in the area radially outside the pivot bearing via a rubber-elastic preferably the gap between the half-lens body to the outside are supported on each other covering intermediate bodies.